Physics
104A Kane Building
University College Cork
Ireland

T: +353 21 490 2452
F: +353 21 427 6949
E: S.Fahy@ucc.ie

Tyndall Theory, Modelling & Design Centre
6.1.36B
Tyndall National Institute
University College Cork
Ireland

T: +353 21 490 4107
F: +353 21 427 6949

I grew up in Cork and took my undergraduate degrees in Mathematical Science and Physics and masters degree in Mathematics at University College Cork. I attended the University of California at Berkeley for my PhD in Physics, where I specialized in condensed matter theory under the supervision of Steven Louie. I was a member of technical staff in the physical science division at Bell Laboratories, 1988-1990. I joined the faculty at the University of Michigan in 1990 and returned to UCC in 1993. 

My research interests are in the theory of electronic properties of solids, particularly semiconductors and semimetals. 

Research Interests

Semiconductor Transport: A major part of my effort in recent years has been given to the formulation of transport in semiconductors in a form to which modern first-principles electronic structure methods can be applied. The systems under study have included conventional semiconductor alloys (SiGe) and the extreme dilute nitride alloys GaAsN and GaInNAs. In collaboration with the group of E. P. O'Reilly, I have investigated the physical origins of poor mobility in the dilute nitrides and have related this to strong band-shifts arising from the presence of nitrogen clusters in these materials. In the conventional alloys, we have calculated for the first time the mobility of a semiconductor alloy, SiGe, from first principles. This represents a major new development in the quantitative understanding of carrier transport in semiconductors.

Vibrational Spectroscopy: The use of vibration mode frequencies as a probe of extreme physical environments has been a recurrent theme in my work, starting with early investigations of the Raman shift in diamond as a gauge for ultra-high pressure in diamond anvil systems. Subsequent work in collaboration with the experimental group of Roy Clarke on the infra-red absorption of cubic boron nitride thin films demonstrated conclusively that these films exhibit islanding in the initial stages of growth and ruled out extreme stress as the instigating factor in the growth of the cubic phase, thereby resolving a long-standing controversy in the field. Seminal work with R. Merlin on the extreme anharmonic excitation of coherent phonons in ferroelectric materials has prompted on-going experimental attempts by several groups to reverse domains on a picosecond time-scale by the application of intense, ultra-short optical pulses. 

My most recent work in this area has investigated impulsive optical excitation of coherent phonons in semiconductors and simulated the resulting pump-probe reflectivity oscillations. Band structure calculations on tellurium and bismuth have demonstrated how their strong electron-phonon coupling is directly related to the Peierls distortion that stabilises the low-pressure phase of these materials. Results of these simulations have been used to understand the diffusion of carriers and their coupling to phonons in optically excited electron-hole plasmas, demonstrating both softening of the phonons at high levels of electronic excitation, slow electron-hole recombination and a substantial reduction in the carrier diffusion rate in the dense plasma. My work on ultrafast coherent dynamics has involved a particularly fruitful interaction with the experimental groups of David Reis, Roberto Merlin and Philip Bucksbaum at the FOCUS centre of the University of Michigan and Stanford University. This has culminated in recent x-ray probe measurements at the Stanford Linear Accelerator, Sub-Picosecond Pulse Source (SPPS), of the energy surface of photo-excited bismuth, which have verified our earlier calculations.

Recent calculations of nitrogen-related localized vibrational modes in dilute nitride semiconductors have provided signature spectra of various defects that are important in determining the microscopic structure and electronic transport properties of these materials. This work has led to a joint experimental-theoretical collaboration with the groups of Rachel Goldman and Cagliyan Kurdak at the University of Michigan. We are currently working on the design and growth of dilute nitride heterostructures in which we plan to use low-temperature transport as a spectroscopic probe of localized state scattering.

Quantum Monte Carlo: In the late 1980s and throughout the 1990s, my work was largely focused on the development of quantum Monte Carlo methods in electronic structure theory. Early work with S. G. Louie and X. W. Wang combined the use of non-local pseudopotentials and variational Monte Carlo methods for the first time in the calculation of electron correlation and chemical binding in solids. This work opened the field for applications in a wide range of materials and has underpinned many subsequent applications of these methods for molecules, clusters and solids. Subsequently with D. R. Hamann, I developed the positive-projection approach for auxiliary-field electronic structure calculations.  This approach inspired a series of developments in Monte Carlo methods for lattice fermion problems, including the constrained-path approach, which has been widely applied in the study of strongly-interacting fermion systems. The work on variational methods  with my research group at UCC culminated in the development of a comprehensive class of methods for the optimisation of the general Jastrow-Slater type of variational many-body wave functions - one of the outstanding theoretical problems in this area.

Noisy Nonlinear Dynamics: Arising out of my work on Monte Carlo sampling methods came a surprising prediction that random external noise may be used to synchronize non-linear dynamical systems under certain conditions. This discovery in the behaviour of complex non-linear systems has subsequently been observed in a variety of systems and has led on to a series of studies by other authors in the area of noisy non-linear systems.

High-Pressure Carbon: My PhD focused on the electronic structure and high-pressure structural properties of carbon in the solid state . This provided the first comprehensive study  of the high-pressure transformations of diamond, which was of importance in understanding the ultimate pressure limits achievable in diamond anvil cells. My analysis of the graphite-diamond transition  was the first quantitative study of energy barriers inhibiting transformation from sp2 to sp3 bonding in condensed carbon systems. In addition, these calculations provided benchmark structural energies, which have been widely used in the parameterization of classical inter-atomic force models of carbon. 

Peer Reviewed Journals

YearPublication
(2017)'Ferroelectric phase transition and the lattice thermal conductivity of Pb(1-x)Ge(x)Te alloys'
R. M. Murphy, E. D. Murray. S. Fahy and I. Savic (2017) 'Ferroelectric phase transition and the lattice thermal conductivity of Pb(1-x)Ge(x)Te alloys'. Physical Review B, 95 (14) [DOI] [Details]
(2017)'Scattering of carriers by coupled plasmon-phonon modes in bulk polar semiconductors and polar semiconductor heterostructures'
A. Hauber and S. Fahy (2017) 'Scattering of carriers by coupled plasmon-phonon modes in bulk polar semiconductors and polar semiconductor heterostructures'. Physical Review B, 95 (4) [DOI] [Details]
(2016)'Broadband phonon scattering in PbTe-based materials driven near ferroelectric phase transition by strain or alloying'
Murphy, RM,Murray, ED,Fahy, S,Savic, I (2016) 'Broadband phonon scattering in PbTe-based materials driven near ferroelectric phase transition by strain or alloying'. Physical Review B, 93 [DOI] [Details]
(2016)'Control of two-phonon correlations and the mechanism of high-wavevector phonon generation by ultrafast light pulses'
Henighan, T,Trigo, M,Chollet, M,Clark, JN,Fahy, S,Glownia, JM,Jiang, MP,Kozina, M,Liu, H,Song, S,Zhu, D,Reis, DA (2016) 'Control of two-phonon correlations and the mechanism of high-wavevector phonon generation by ultrafast light pulses'. Physical Review B, 94 [DOI] [Details]
(2016)'Resonant squeezing and the anharmonic decay of coherent phonons'
Fahy, S,Murray, ED,Reis, DA (2016) 'Resonant squeezing and the anharmonic decay of coherent phonons'. Physical Review B, 93 [DOI] [Details]
(2016)'The origin of incipient ferroelectricity in lead telluride'
Jiang, M. P.; Trigo, M.; Savić, Ivana; Fahy, Stephen B.; Murray, Éamonn D.; Bray, C.; Clark, J.; Henighan, T.; Kozina, M.; Chollet, M.; Glownia, J. M.; Hoffmann, M. C.; Zhu, D.; Delaire, O.; May, A. F.; Sales, B. C.; Lindenberg, A. M.; Zalden, P.; Sato, T.; Merlin, R.; Reis, D. A. (2016) 'The origin of incipient ferroelectricity in lead telluride'. Nature Communications, 7 [DOI] [CORA Link] [Details]
(2015)'First-Principles Calculation of Femtosecond Symmetry-Breaking Atomic Forces in Photoexcited Bismuth'
Murray, ED;Fahy, S (2015) 'First-Principles Calculation of Femtosecond Symmetry-Breaking Atomic Forces in Photoexcited Bismuth'. Physical Review Letters, 114 [DOI] [Details]
(2014)'Optical Absorption of dilute nitride alloys using self-consistent Green's function method'
M. Seifikar, E. P. O'Reilly and S. Fahy (2014) 'Optical Absorption of dilute nitride alloys using self-consistent Green's function method'. Nanoscale Research Letters, 9 Globe icon [DOI] [Details]
(2014)'Self-consistent Green's function method for dilute nitride conduction band structure'
Seifikar, M,O'Reilly, EP,Fahy, S (2014) 'Self-consistent Green's function method for dilute nitride conduction band structure'. Journal of Physics-Condensed Matter, 26 [DOI] [Details]
(2013)'Optical Probing of Ultrafast Electronic Decay in Bi and Sb with Slow Phonons'
Li, JJ,Chen, J,Reis, DA,Fahy, S,Merlin, R (2013) 'Optical Probing of Ultrafast Electronic Decay in Bi and Sb with Slow Phonons'. Physical Review Letters, 110 [DOI] [Details]
(2013)'Fourier-transform inelastic X-ray scattering from time- and momentum-dependent phonon-phonon correlations'
Trigo, M,Fuchs, M,Chen, J,Jiang, MP,Cammarata, M,Fahy, S,Fritz, DM,Gaffney, K,Ghimire, S,Higginbotham, A,Johnson, SL,Kozina, ME,Larsson, J,Lemke, H,Lindenberg, AM,Ndabashimiye, G,Quirin, F,Sokolowski-Tinten, K,Uher, C,Wang, G,Wark, JS,Zhu, D,Reis, DA (2013) 'Fourier-transform inelastic X-ray scattering from time- and momentum-dependent phonon-phonon correlations'. Nature Physics, 9 :790-794 [DOI] [Details]
(2013)'Time- and momentum-resolved probe of heat transport in photo-excited bismuth'
Chen, J,Trigo, M,Fahy, S,Murray, ED,Sheu, YM,Graber, T,Henning, R,Chien, YJ,Uher, C,Reis, DA (2013) 'Time- and momentum-resolved probe of heat transport in photo-excited bismuth'. Applied Physics Letters, 102 [DOI] [Details]
(2013)'Free-carrier relaxation and lattice heating in photoexcited bismuth'
Sheu, YM,Chien, YJ,Uher, C,Fahy, S,Reis, DA (2013) 'Free-carrier relaxation and lattice heating in photoexcited bismuth'. Physical Review B, 87 [DOI] [Details]
(2012)'First-principles investigation of the alloy scattering potential in dilute Si1−xCx'
Vaughan, MP; F. Murphy-Armando, F; Fahy S (2012) 'First-principles investigation of the alloy scattering potential in dilute Si1−xCx'. Physical Review B, 82 [DOI] [Details]
(2012)'Giant piezoresistance in silicon-germanium alloys'
Murphy-Armando, F. and Fahy, S. (2012) 'Giant piezoresistance in silicon-germanium alloys'. Physical Review B, 86 (3) [Details]
(2012)'How reflected wave fronts dynamically establish Hooke's law in a spring'
Fahy, S,O'Riordan, J,O'Sullivan, C,Twomey, P (2012) 'How reflected wave fronts dynamically establish Hooke's law in a spring'. European Journal of Physics, 33 :417-426 [DOI] [Details]
(2012)'Giant enhancement of n-type carrier mobility in highly strained germanium nanostructures (vol 109, 113703, 2011)'
Murphy-Armando, F,Fahy, S (2012) 'Giant enhancement of n-type carrier mobility in highly strained germanium nanostructures (vol 109, 113703, 2011)'. Journal of Applied Physics, 112 [DOI] [Details]
(2011)'First principles calculation of electron-phonon and alloy scattering in strained SiGe'
Murphy-Armando, F. and Fahy, S. (2011) 'First principles calculation of electron-phonon and alloy scattering in strained SiGe'. Journal of Applied Physics, 110 (12):123706-123706 [CORA Link] [Details]
(2011)'Effect of strain on the deformation potentials in Ge-like SiGe'
Murphy-Armando, F. and Fahy, S. (2011) 'Effect of strain on the deformation potentials in Ge-like SiGe'. Chinese Journal of Physics, 49 (1) [Details]
(2011)'Modelling and direct measurement of the density of states in GaAsN'
Vaughan, MP,Fahy, S,O'Reilly, EP,Ivanova, L,Eisele, H,Dahne, M; (2011) 'Modelling and direct measurement of the density of states in GaAsN'. Physica Status Solidi B-Basic Solid State Physics, 248 :1167-1171 [DOI] [Details]
(2011)'Giant enhancement of n-type carrier mobility in highly strained germanium nanostructures'
Murphy-Armando, F. and Fahy, S. (2011) 'Giant enhancement of n-type carrier mobility in highly strained germanium nanostructures'. Journal of Applied Physics, 109 [CORA Link] [Details]
(2011)'Theory of intermediate- and high-field mobility in dilute nitride alloys'
Seifikar, M,O'Reilly, EP,Fahy, S (2011) 'Theory of intermediate- and high-field mobility in dilute nitride alloys'. Physical Review B, 84 [DOI] [Details]
(2011)'Mobility in gated GaNxAs1-x heterostructures as a probe of nitrogen-related electronic states'
Buckeridge, J,Fahy, S (2011) 'Mobility in gated GaNxAs1-x heterostructures as a probe of nitrogen-related electronic states'. Physical Review B, 84 [DOI] [Details]
(2011)'Analysis of band-anticrossing model in GaNAs near localised states'
Seifikar, M,O'Reilly, EP,Fahy, S; (2011) 'Analysis of band-anticrossing model in GaNAs near localised states'. Physica Status Solidi B-Basic Solid State Physics, 248 :1176-1179 [DOI] [Details]
(2010)'Comment on ``Directly Observing Squeezed Phonon States with Femtosecond X-Ray Diffraction'' Reply'
Johnson, SL; Beaud, P; Vorobeva, E; Milne, CJ; Murray, ED; Fahy, S; Ingold, G; (2010) 'Comment on ``Directly Observing Squeezed Phonon States with Femtosecond X-Ray Diffraction'' Reply'. Physical Review Letters, 104 (2) [DOI] [Details]
(2010)'Comment on Directly Observing Squeezed Phonon States with Femtosecond X-Ray Diffraction'' Reply'
Johnson, SL; Beaud, P; Vorobeva, E; Milne, CJ; Murray, ED; Fahy, S; Ingold, G; (2010) 'Comment on Directly Observing Squeezed Phonon States with Femtosecond X-Ray Diffraction'' Reply'. Physical Review Letters, 104 Globe icon [DOI] [Details]
(2010)'Vibrational signature of the Si-N defect in Si-doped GaNxAs1-x'
Buckeridge, J,O'Halloran, S,Fahy, S; (2010) 'Vibrational signature of the Si-N defect in Si-doped GaNxAs1-x'. Solid State Communications, 150 :1967-1970 [DOI] [Details]
(2010)'Nitrogen composition dependence of electron effective mass in GaAs1-xNx'
Dannecker, T,Jin, Y,Cheng, H,Gorman, CF,Buckeridge, J,Uher, C,Fahy, S,Kurdak, C,Goldman, RS; (2010) 'Nitrogen composition dependence of electron effective mass in GaAs1-xNx'. Physical Review B, 82 [DOI] [Details]
(2010)'Direct measurement and analysis of the conduction band density of states in diluted GaAs1-xNx alloys'
Ivanova, L,Eisele, H,Vaughan, MP,Ebert, P,Lenz, A,Timm, R,Schumann, O,Geelhaar, L,Dahne, M,Fahy, S,Riechert, H,O'Reilly, EP; (2010) 'Direct measurement and analysis of the conduction band density of states in diluted GaAs1-xNx alloys'. Physical Review B, 82 [DOI] [Details]
(2010)'Non-equilibrium phonon dynamics studied by grazing-incidence femtosecond X-ray crystallography'
Johnson, SL,Beaud, P,Vorobeva, E,Milne, CJ,Murray, ED,Fahy, S,Ingold, G; (2010) 'Non-equilibrium phonon dynamics studied by grazing-incidence femtosecond X-ray crystallography'. Acta Crystallographica Section A, 66 :157-167 [DOI] [Details]
(2009)'Vibrational mode shifts as a measure of local strain in the dilute nitride semiconductor alloy GaNxAs1-x'
Buckeridge, J. and Teweldeberhan, A. M. and Fahy, S.; (2009) 'Vibrational mode shifts as a measure of local strain in the dilute nitride semiconductor alloy GaNxAs1-x'. PHYSICAL REVIEW B, 79 (15) [DOI] [Details]
(2009)'Directly Observing Squeezed Phonon States with Femtosecond X-Ray Diffraction'
Johnson, SL,Beaud, P,Vorobeva, E,Milne, CJ,Murray, ED,Fahy, S,Ingold, G; (2009) 'Directly Observing Squeezed Phonon States with Femtosecond X-Ray Diffraction'. Physical Review Letters, 102 [DOI] [Details]
(2009)'Observation of Insulating Nanoislands in Ferromagnetic GaMnAs'
Wang, DM,Ren, YH,Jacobs, PW,Fahy, S,Liu, X,Furdyna, JK,Sapega, VF,Merlin, R (2009) 'Observation of Insulating Nanoislands in Ferromagnetic GaMnAs'. Physical Review Letters, 102 [DOI] [Details]
(2009)'Optical transitions in dilute GaNxAs1-x nitrides: A comparison between ab initio and empirical pseudopotentials'
Stenuit, G,Fahy, S (2009) 'Optical transitions in dilute GaNxAs1-x nitrides: A comparison between ab initio and empirical pseudopotentials'. Journal Of Physics And Chemistry Of Solids, 70 :769-777 [DOI] [Details]
(2008)'Resonant Raman Study of Local Vibration Modes In Algaasn Layers'
Gallardo, E, Lazic, S, Calleja, JM, Miguel-Sanchez, J, Montes, M, Hierro, A, Gargallo-Caballero, R, Guzman, A, Munoz, E, Teweldeberhan, AM, Fahy, S; (2008) 'Resonant Raman Study of Local Vibration Modes In Algaasn Layers'. Physica E-Low-Dimensional Systems & Nanostructures, 40 (6):2084-2086 [DOI] [Details]
(2008)'Effect of nitrogen interactions on photoluminescence linewidth broadening in dilute nitride semiconductors'
Bosa, I,McPeake, D,Fahy, S (2008) 'Effect of nitrogen interactions on photoluminescence linewidth broadening in dilute nitride semiconductors'. Physical Review B, 78 [DOI] [Details]
(2008)'Phonon spectra of the high-frequency modes in dilute nitride random GaNxAs1-x alloy'
Teweldeberhan, AM,Fahy, S; (2008) 'Phonon spectra of the high-frequency modes in dilute nitride random GaNxAs1-x alloy'. Physical Review B, 77 [DOI] [Details]
(2008)'Resonant Raman-active localized vibrational modes in AlyGa1-yNxAs1-x alloys: Experiment and first-principles calculations'
Teweldeberhan, AM,Stenuit, G,Fahy, S,Gallardo, E,Lazic, S,Calleja, JM,Miguel-Sanchez, J,Montes, M,Hierro, A,Gargallo-Caballero, R,Guzman, A,Munoz, E; (2008) 'Resonant Raman-active localized vibrational modes in AlyGa1-yNxAs1-x alloys: Experiment and first-principles calculations'. Physical Review B, 77 [DOI] [Details]
(2008)'First-principles calculation of carrier-phonon scattering in n-type Si\_ $$1- x$\$ Ge\_ $$x$\$ alloys'
Murphy-Armando, F. and Fahy, S. (2008) 'First-principles calculation of carrier-phonon scattering in n-type Si\_ $$1- x$\$ Ge\_ $$x$\$ alloys'. Physical Review B, 78 (3) [Details]
(2007)'First-principles calculations of the mechanical and structural properties of GaNxAs1-x: Lattice and elastic constants'
Stenuit, G,Fahy, S; (2007) 'First-principles calculations of the mechanical and structural properties of GaNxAs1-x: Lattice and elastic constants'. Physical Review B, 76 [DOI] [Details]
(2007)'Ultrafast bond softening in bismuth: Mapping a solid's interatomic potential with X-rays'
Fritz, DM,Reis, DA,Adams, B,Akre, RA,Arthur, J,Blome, C,Bucksbaum, PH,Cavalieri, AL,Engemann, S,Fahy, S,Falcone, RW,Fuoss, PH,Gaffney, KJ,George, MJ,Hajdu, J,Hertlein, MP,Hillyard, PB,Hoegen, MHV,Kammler, M,Kaspar, J,Kienberger, R,Krejcik, P,Lee, SH,Lindenberg, AM,McFarland, B,Meyer, D,Montagne, T,Murray, ED,Nelson, AJ,Nicoul, M,Pahl, R,Rudati, J,Schlarb, H,Siddons, DP,Sokolowski-Tinten, K,Tschentscher, T,von der Linde, D,Hastings, JB; (2007) 'Ultrafast bond softening in bismuth: Mapping a solid's interatomic potential with X-rays'. Science, 315 :633-636 [DOI] [Details]
(2007)'Phonon Dispersion Relations and Softening In Photoexcited Bismuth From First Principles'
Murray, ED, Fahy, S, Prendergast, D, Ogitsu, T, Fritz, DM, Reis, DA; (2007) 'Phonon Dispersion Relations and Softening In Photoexcited Bismuth From First Principles'. Physical Review B, 75 (18) [DOI] [Details]
(2007)'Calculated mechanical and structural properties of GaNxAs1-x'
G. Stenuit and S. Fahy; (2007) 'Calculated mechanical and structural properties of GaNxAs1-x'. Physical Review B, [Details]
(2007)'First-principles calculation of p-type alloy scattering in Si\_ $$1- x$\$ Ge\_ $$x$\$'
Joyce, S. and Murphy-Armando, F. and Fahy, S. (2007) 'First-principles calculation of p-type alloy scattering in Si\_ $$1- x$\$ Ge\_ $$x$\$'. Physical Review B, 75 (15) [Details]
(2006)'Effect of indium-nitrogen bonding on the localized vibrational mode in Iny Ga1-y Nx As1-x'
Teweldeberhan, A. M. and Fahy, S. ; (2006) 'Effect of indium-nitrogen bonding on the localized vibrational mode in Iny Ga1-y Nx As1-x'. Phys. Rev. B, 73 (24) [DOI] [Details]
(2006)'Simulations of Time-Resolved X-Ray Diffraction In Laue Geometry'
Lings, B, Wark, JS, DeCamp, MF, Reis, DA, Fahy, S; (2006) 'Simulations of Time-Resolved X-Ray Diffraction In Laue Geometry'. Journal of Physics-Condensed Matter, 18 (40):9231-9244 [DOI] [Details]
(2006)'Effect of indium-nitrogen bonding on the localized vibrational mode in InyGa1-yNxAs1-x'
Teweldeberhan, AM,Fahy, S (2006) 'Effect of indium-nitrogen bonding on the localized vibrational mode in InyGa1-yNxAs1-x'. Physical Review B, 73 [DOI] [Details]
(2006)'Alloy scattering of n-type carriers in GaNxAs1-x'
Fahy, S,Lindsay, A,Ouerdane, H,O'Reilly, EP; (2006) 'Alloy scattering of n-type carriers in GaNxAs1-x'. Physical Review B, 74 [DOI] [Details]
(2006)'Alloy scattering of n -type carriers in GaN_xAs_1-x'
Fahy, S., Lindsay, A., Ouerdane, H., O'Reilly, E.P.; (2006) 'Alloy scattering of n -type carriers in GaN_xAs_1-x'. Physical Review B, 74 (3) Globe icon [DOI] [Details]
(2006)'First-Principles Calculation of Alloy Scattering in Ge_xSi_1-x'
Murphy-Armando, F. and Fahy, S.; (2006) 'First-Principles Calculation of Alloy Scattering in Ge_xSi_1-x'. Physical Review Letters, 97 (9) Globe icon [DOI] [CORA Link] [Details]
(2006)'First-Principles Calculation of Alloy Scattering in Ge\_ $$x$\$ Si\_ $$1-x$\$'
Murphy-Armando, F. and Fahy, S. (2006) 'First-Principles Calculation of Alloy Scattering in Ge\_ $$x$\$ Si\_ $$1-x$\$'. Physical review letters, 97 (9) [Details]
(2005)'Effect of lattice anharmonicity on high-amplitude phonon dynamics in photoexcited bismuth'
E. D. Murray, D. M. Fritz, J. K. Wahlstrand, S. Fahy and D. A. Reis; (2005) 'Effect of lattice anharmonicity on high-amplitude phonon dynamics in photoexcited bismuth'. Physical Review B: Rapid Communications, 72 (6) Globe icon [DOI] [Details]
(2005)'Calculated pressure dependence of the localized vibrational mode of nitrogen in GaNxAs1-x'
Teweldeberhan, AM,Fahy, S (2005) 'Calculated pressure dependence of the localized vibrational mode of nitrogen in GaNxAs1-x'. Physical Review B, 72 [DOI] [Details]
(2004)'Coherent phonons: Electronic softening or anharmonicity?'
Fahy, S,Reis, DA (2004) 'Coherent phonons: Electronic softening or anharmonicity?'. Physical Review Letters, 93 [DOI] [Details]
(2004)'Theory of the electronic structure of dilute nitride alloys: beyond the band-anti-crossing model'
O'Reilly, EP,Lindsay, A,Fahy, S; (2004) 'Theory of the electronic structure of dilute nitride alloys: beyond the band-anti-crossing model'. Journal of Physics-Condensed Matter, 16 :3257-3276 [DOI] [Details]
(2004)'Intrinsic limits on electron mobility in disordered dilute nitride semiconductor alloys'
S. Fahy, A. Lindsay and E. P. O'Reilly; (2004) 'Intrinsic limits on electron mobility in disordered dilute nitride semiconductor alloys'. IEE Proceedings Optoelectronics, 151 (5):352-356 [DOI] [Details]
(2004)'Theory of electron mobility in dilute nitride semiconductors'
Fahy, S,O'Reilly, EP (2004) 'Theory of electron mobility in dilute nitride semiconductors'. Physica E-Low-Dimensional Systems & Nanostructures, 21 :881-885 [DOI] [Details]
(2003)'Transient strain driven by a dense electron-hole plasma'
DeCamp, MF,Reis, DA,Cavalieri, A,Bucksbaum, PH,Clarke, R,Merlin, R,Dufresne, EM,Arms, DA,Lindenberg, AM,MacPhee, AG,Chang, Z,Lings, B,Wark, JS,Fahy, S (2003) 'Transient strain driven by a dense electron-hole plasma'. Physical Review Letters, 91 [DOI] [Details]
(2003)'Intrinsic limits on electron mobility in dilute nitride semiconductors'
Fahy S, O'Reilly EP; (2003) 'Intrinsic limits on electron mobility in dilute nitride semiconductors'. Applied Physics Letters, 83 (18):3731-3733 [DOI] [Details]
(2002)'Optimization of configuration interaction coefficients in multideterminant Jastrow-Slater wave functions'
Schautz, F,Fahy, S (2002) 'Optimization of configuration interaction coefficients in multideterminant Jastrow-Slater wave functions'. The Journal of chemical physics, 116 :3533-3539 [DOI] [Details]
(2002)'Optimization of inhomogeneous electron correlation factors in periodic solids'
Prendergast D, Bevan D, Fahy S; (2002) 'Optimization of inhomogeneous electron correlation factors in periodic solids'. Physical Review B: Condensed Matter, 66 (15):155104-* Globe icon [DOI] [Details]
(2002)'Density-functional theory approach to ultrafast laser excitation of semiconductors: Application to the A(1) phonon in tellurium'
Tangney P, Fahy S; (2002) 'Density-functional theory approach to ultrafast laser excitation of semiconductors: Application to the A(1) phonon in tellurium'. Physical Review B: Condensed Matter, 65 (5):054302-* Globe icon [DOI] [Details]
(2001)'Impact of electron-electron cusp on configuration interaction energies'
Prendergast, D,Nolan, M,Filippi, C,Fahy, S,Greer, JC (2001) 'Impact of electron-electron cusp on configuration interaction energies'. The Journal of chemical physics, 115 :1626-1634 [Details]
(2000)'Optimal orbitals from energy fluctuations in correlated wave functions'
Filippi C. and Fahy S.; (2000) 'Optimal orbitals from energy fluctuations in correlated wave functions'. Journal of Chemical Physics, 112 (8):3523-3531 [DOI] [Details]
(2000)'Alloy corrections to the virtual crystal approximation and explicit band structure calculations for silicon-germanium'
Fahy, S,Greer, JC (2000) 'Alloy corrections to the virtual crystal approximation and explicit band structure calculations for silicon-germanium'. Materials Science In Semiconductor Processing, 3 :109-114 [Details]
(1999)'Calculations of the A(1) phonon frequency in photoexcited tellurium'
Tangney P, Fahy S; (1999) 'Calculations of the A(1) phonon frequency in photoexcited tellurium'. Physical Review Letters, 82 (21):4340-4343 Globe icon [DOI] [Details]
(1998)'Onset of chaos in a pendulum coupled to a thermal environment'
Fahy, S,Twohig, S,Stefansson, M,Courtney, D; (1998) 'Onset of chaos in a pendulum coupled to a thermal environment'. Physical Review E, 57 :2799-2810 [Details]
(1997)'Variational quantum Monte Carlo calculation of the cohesive properties of cubic boron nitride'
Malatesta, A,Fahy, S,Bachelet, GB; (1997) 'Variational quantum Monte Carlo calculation of the cohesive properties of cubic boron nitride'. Physical Review B, 56 :12201-12210 [Details]
(1997)'Islanding and Strain-Induced Shifts in the Infrared Absorption Peaks of Cubic Boron Nitride Thin Films'
Fahy, S. B.; Taylor, C. A.; Clarke, R.; (1997) 'Islanding and Strain-Induced Shifts in the Infrared Absorption Peaks of Cubic Boron Nitride Thin Films'. Physical Review B: Condensed Matter, 56 (19):12573-12580 Globe icon [DOI] [Details]
(1996)'Variational Monte Carlo on a Parallel Architecture: an Application to Graphite'
Menchi, M.; Bosin, A.; Fahy, S. B.; (1996) 'Variational Monte Carlo on a Parallel Architecture: an Application to Graphite'. Materials Research Society Symposia Proceedings, 408 :169-174 [Details]
(1995)'Strain-Induced Shifts in the Infra-Red Absorption Peaks of Boron Nitride'
Fahy, S.; (1995) 'Strain-Induced Shifts in the Infra-Red Absorption Peaks of Boron Nitride'. Physical Review B: Rapid Communications, 51 (18):12873-12876 Globe icon [DOI] [Details]
(1995)'IMPULSIVE LIGHT-SCATTERING BY COHERENT PHONONS IN LAALO3 - DISORDER AND BOUNDARY EFFECTS'
LIU, Y,FRENKEL, A,GARRETT, GA,WHITAKER, JF,FAHY, S,UHER, C,MERLIN, R; (1995) 'IMPULSIVE LIGHT-SCATTERING BY COHERENT PHONONS IN LAALO3 - DISORDER AND BOUNDARY EFFECTS'. Physical Review Letters, 75 :334-337 [Details]
(1994)'REVERSAL OF FERROELECTRIC DOMAINS BY ULTRASHORT OPTICAL PULSES'
FAHY, S,MERLIN, R; (1994) 'REVERSAL OF FERROELECTRIC DOMAINS BY ULTRASHORT OPTICAL PULSES'. Physical Review Letters, 73 :1122-1125 [Details]
(1994)'SIMPLE EFFECTIVE-MASS MODEL TO INCLUDE THE EFFECTS OF GAMMA-X MIXING IN MULTIQUANTUM BARRIERS'
MORRISON, AP,LAMBKIN, JD,OSULLIVAN, E,FAHY, S; (1994) 'SIMPLE EFFECTIVE-MASS MODEL TO INCLUDE THE EFFECTS OF GAMMA-X MIXING IN MULTIQUANTUM BARRIERS'. Optical Engineering, 33 :3926-3930 [Details]
(1994)'Molecular Dynamics Study of Single-Atom Radiation Damage in Diamond'
Wu, W.; Fahy, S. ; (1994) 'Molecular Dynamics Study of Single-Atom Radiation Damage in Diamond'. Physical Review B: Condensed Matter, 49 (5):3030-3035 Globe icon [DOI] [Details]
(1993)'Long-Range Interactions in Auxiliary-Field Many-Electron Calculations'
Hamann, D. R.; Fahy, S. B.; (1993) 'Long-Range Interactions in Auxiliary-Field Many-Electron Calculations'. Physical Review B: Condensed Matter, 47 (4):1717-1725 Globe icon [DOI] [Details]
(1992)'Transition From Chaotic to Non-Chatoic Behavior in Randomly Driven Systems'
Fahy, S. B.; Hamann, D. R.; (1992) 'Transition From Chaotic to Non-Chatoic Behavior in Randomly Driven Systems'. Physical Review Letters, 69 (5):761-764 Globe icon [DOI] [Details]
(1991)'Diffusive behavior of states in the Hubbard-Stratonovitch transformation'
Fahy S, Hamann D.R.; (1991) 'Diffusive behavior of states in the Hubbard-Stratonovitch transformation'. Physical Review B: Condensed Matter, 43 (1):765-779 Globe icon [DOI] [Details]
(1990)'Electronic and structural properties of CaSi2'
S. Fahy and D. R. Hamann ; (1990) 'Electronic and structural properties of CaSi2'. Physical Review B, 41 (11):7587-7592 [DOI] [Details]
(1990)'Energy measurement in auxiliary-field many-electron calculations'
Hamann DR, Fahy SB; (1990) 'Energy measurement in auxiliary-field many-electron calculations'. Physical Review B, 41 (16):11352-11363 Globe icon [DOI] [Details]
(1990)'Positive-projection Monte Carlo simulation: A new variational approach to strongly interacting fermion systems'
FAHY SB, HAMANN DR; (1990) 'Positive-projection Monte Carlo simulation: A new variational approach to strongly interacting fermion systems'. Physical Review Letters, 65 (27):3437-3440 Globe icon [DOI] [Details]
(1990)'Variational quantum Monte Carlo nonlocal pseudopotential approach to solids: Formulation and application to diamond, graphite, and silicon'
S. Fahy, X. W. Wang and Steven G. Louie; (1990) 'Variational quantum Monte Carlo nonlocal pseudopotential approach to solids: Formulation and application to diamond, graphite, and silicon'. Physical Review B, 42 (6):3503-3522 [DOI] [Details]
(1990)'Magnetic structure and equation of state of bcc solid hydrogen: A variational quantum Monte Carlo study'
Wang XW, Zhu J, Louie SG, Fahy S; (1990) 'Magnetic structure and equation of state of bcc solid hydrogen: A variational quantum Monte Carlo study'. Physical Review Letters, 65 (19):2414-2417 Globe icon [DOI] [Details]
(1989)'Ab initio calculation of pressure coefficients of band gaps of silicon: Comparison of the local-density approximation and quasiparticle results'
Xuejun Zhu, S. Fahy, and Steven G. Louie ; (1989) 'Ab initio calculation of pressure coefficients of band gaps of silicon: Comparison of the local-density approximation and quasiparticle results'. Physical Review B, 39 (11):7840-7847 [DOI] [Details]
(1988)'Ab initio study of graphite --> diamondlike transitions in BN'
Wentzcovitch RM, Fahy S, Cohen ML, Louie SG; (1988) 'Ab initio study of graphite --> diamondlike transitions in BN'. Physical Review B, 38 (9):6191-6195 [DOI] [Details]
(1988)'Variational quantum Monte Carlo nonlocal pseudopotential approach to solids: Cohesive and structural properties of diamond'
Fahy S, Wang XW, Louie SG; (1988) 'Variational quantum Monte Carlo nonlocal pseudopotential approach to solids: Cohesive and structural properties of diamond'. Physical Review Letters, 61 (14):1631-1634 [DOI] [Details]
(1988)'Electromagnetic screening by metals'
S. Fahy and Charles Kittel and Steven G. Louie; (1988) 'Electromagnetic screening by metals'. American Journal of Physics, 56 (11):989-992 Globe icon [Details]
(1988)'Magnetic screening by a thin superconducting surface layer'
Kittel C, Fahy S, Louie SG; (1988) 'Magnetic screening by a thin superconducting surface layer'. Physical Review B, 37 (1):642-643 [DOI] [Details]
(1987)'Pressure coefficients of band gaps of diamond'
Fahy S, Chang KJ, Louie SG, Cohen ML; (1987) 'Pressure coefficients of band gaps of diamond'. Physical Review B, 35 (11):5856-5859 Globe icon [DOI] [Details]
(1987)'Theoretical total-energy study of the transformation of graphite into hexagonal diamond'
Fahy S, Louie SG, Cohen ML; (1987) 'Theoretical total-energy study of the transformation of graphite into hexagonal diamond'. Physical Review B, 35 (14):7623-7626 Globe icon [DOI] [Details]
(1987)'High-pressure structural and electronic properties of carbon'
Fahy, S. and Louie, Steven G.; (1987) 'High-pressure structural and electronic properties of carbon'. Phys. Rev. B, 36 (6):3373-3385 Globe icon [DOI] [Details]
(1987)'Probing electronic density of states and magnetic interactions at the rare-earth site in ErBa2Cu3O7'
Walter U, Fahy S, Zettl A, Louie SG, Cohen ML, Tejedor P, Stacy AM; (1987) 'Probing electronic density of states and magnetic interactions at the rare-earth site in ErBa2Cu3O7'. Physical Review B, 36 (16):8899-8902 [Details]
(1986)'Pseudopotential total-energy study of the transition from rhombohedral graphite to diamond'
Fahy S, Louie SG, Cohen ML; (1986) 'Pseudopotential total-energy study of the transition from rhombohedral graphite to diamond'. Physical Review B, 34 (2):1191-1199 [Details]
(1986)'The first-order Raman mode of diamond under pressure'
M. Hanfland and K. Syassen and S. Fahy and Steven G. Louie and Marvin L. Cohen; (1986) 'The first-order Raman mode of diamond under pressure'. Physica B+C, 139-140 :516-519 Globe icon [DOI] [Details]
(1985)'Pressure dependence of the first-order Raman mode in diamond'
Hanfland M, Syassen K, Fahy S, Louie SG, Cohen ML; (1985) 'Pressure dependence of the first-order Raman mode in diamond'. Physical Review B, 31 (10):6896-6899 [Details]

Book Chapters

YearPublication
(1996)'Quantum Monte Carlo Methods'
Fahy, S.B.; (1996) 'Quantum Monte Carlo Methods' In: Quantum Theory of Real Materials. Massachusetts: Kluwer Academic Publishing. [Details]
(1993)'Ground State Projection With Auxiliary Fields: Imaginary-Time and Simulation-Time Dynamics'
Fahy, S.B.; (1993) 'Ground State Projection With Auxiliary Fields: Imaginary-Time and Simulation-Time Dynamics' In: Computer Simulation Studies in Condensed Matter Physics VI. New York: Springer. [Details]
(1993)'Ground-State Projection Using Auxiliary Fields'
Fahy, S.B.; (1993) 'Ground-State Projection Using Auxiliary Fields' In: Quantum Monte Carlo Methods in Condensed Matter Physics. Singapore: World Scientific. [Details]

Other Journals

YearPublication
(2010)'First principles calculations of the scattering cross section of substitutional carbon in silicon'
Vaughan, MP; Fahy, S (2010) 'First principles calculations of the scattering cross section of substitutional carbon in silicon' Journal of Physics: Conference Series, 242 . [DOI] [Details]
(2009)'Viewpoint: Squeezing more out of ultrafast x-ray measurements'
Johnson, SL and Beaud, P and Vorobeva, E and Milne, CJ and Murray, \'ED and Fahy, S and Ingold, G (2009) 'Viewpoint: Squeezing more out of ultrafast x-ray measurements' Phys. Rev. Lett, 102 . [Details]

Conference Publications

YearPublication
(2012)Ultimate Integration on Silicon (ULIS), 2012 13th International Conference on
Murphy-Armando, F. and Fahy, S. (2012) Very large piezoresistance in Si 1- x Ge x alloys Ultimate Integration on Silicon (ULIS), 2012 13th International Conference on , pp.117-120 [Details]
(2011)Ultimate Integration on Silicon (ULIS), 2011 12th International Conference on
Murphy-Armando, F. and Fahy, S. (2011) Giant mobility enhancement in highly strained, direct gap Ge Ultimate Integration on Silicon (ULIS), 2011 12th International Conference on , pp.1-3 [Details]
(2011)Ultimate Integration on Silicon (ULIS), 2011 12th International Conference on
Vaughan, MP and Murphy-Armando, F. and Fahy, S. (2011) Alloy scattering of substitutional carbon in silicon: a first principles approach Ultimate Integration on Silicon (ULIS), 2011 12th International Conference on , pp.1-4 [Details]
(2005)27th Int. Conf. on the Physics of Semiconductors
A. Lindsay, S. Fahy and E.P. O'Reilly; (2005) Theory Of Electron Effective Mass And Mobility in Dilute Nitride Alloys . In: Menédez and C.G. Van de Walle eds. 27th Int. Conf. on the Physics of Semiconductors [Details]
(2004)Intrinsic limits on electron mobility in disordered dilute nitride semiconductor alloys
Fahy, S,Lindsay, A,O'Reilly, EP (2004) IEE PROCEEDINGS-OPTOELECTRONICS Intrinsic limits on electron mobility in disordered dilute nitride semiconductor alloys , pp.352-356 [DOI] [Details]
(2003)26th Int. Conf. on the Physics of Semiconductors
S. Fahy and E. P. O'Reilly; (2003) Scattering of Carriers by Nitrogen Defects in GaAs . In: A. R. Long and J. H. Davies eds. 26th Int. Conf. on the Physics of Semiconductors [Details]
(1994)18th European Workshop on Compound Semiconductor Devices and Integrated Circuits (WOCSDICE)
A. P. Morrison , J. D. Lambkin, E. O'Sullivan and S. Fahy; (1994) Design of a multiquantum barrier using an extended effective mass model to include the effects of G-X mixing . In: * eds. 18th European Workshop on Compound Semiconductor Devices and Integrated Circuits (WOCSDICE) Kinsale, Ireland, , 29-MAY-94 - 01-JUN-94 , pp.91-91 [Details]
(1988)19th Int. Conf. Phys. of Semicond
S. Fahy, X. W. Wang, and S. G. Louie; (1988) Quantum Monte Carlo calculation of the properties of atomic carbon and diamond . In: W. Zawadzki eds. 19th Int. Conf. Phys. of Semicond Warsaw, Poland, [Details]

Published Reports

YearPublication
(1987)Variational Monte Carlo sampling of the superconducting ground state.
S. Fahy and S. G. Louie; (1987) Variational Monte Carlo sampling of the superconducting ground state. Lawrence Berkeley Laboratory, Lawrence Berkeley Laboratory. [Details]

Thesis/Dissertation

YearPublication
(1987)Electronic properties, structural phase transitions, and bonding of carbon in the solid state.
S. Fahy; (1987) Electronic properties, structural phase transitions, and bonding of carbon in the solid state. Thesis/Dissertation [Details]

Honours and Awards

 YearTitleAwarding Body
2005Fellow of the American Physical Society American Physical Society
1985Victor Lenzen Scholarship, University of California UC, Berkeley
1982Regents Fellowship, University of California UC, Berkeley
1981Travelling Studentship in Mathematical Science, National University of Ireland National University of Ireland
1976College Scholarship, University College Cork University College Cork

Professional Associations

 AssociationFunctionFrom / To
American Physical Society Fellow/

Patents

 Patent NumberTitleGranted
5,477,519Data storage using pulsed optical domain reversal 19-DEC-95

Conference Contributions

YearPublication
(2012)Piezo-resistance in $ n $-type Si $ \_ $$1-x$\$ $ Ge $ \_x $ alloys as a function of alloy composition and strain,
Murphy-Armando, F. and Fahy, S. (2012) APS. [Oral Presentation], Piezo-resistance in $ n $-type Si $ \_ $$1-x$\$ $ Ge $ \_x $ alloys as a function of alloy composition and strain, Boston , 27-FEB-12 - 02-MAR-12. [Details]
(2007)Irish Atomistic Simulation Conference,
S.Fahy; (2007) Conference Organization. [Conference Organising Committee Chairperson], Irish Atomistic Simulation Conference, Cork , 12-DEC-07 - 14-DEC-07. [Details]
(2006)First-principles calculation of phonon scattering of n-type carriers in SiGe alloys,
Murphy Armando, F. and Fahy, S. (2006) First-principles calculation of phonon scattering of n-type carriers in SiGe alloys, . [Details]
(2006)Hole mobility in SiGe alloys from first principles,
Joyce, S. and Murphy-Armando, F. and Fahy, S. (2006) Hole mobility in SiGe alloys from first principles, . [Details]
(2005)First-principles calculation of alloy scattering of n-type carriers in SiGe,
Murphy-Armando, F. and Fahy, S. (2005) First-principles calculation of alloy scattering of n-type carriers in SiGe, . [Details]
(2004)Irish Atomistic Simulation Conference,
S.Fahy; (2004) Conference Organization. [Conference Organising Committee Chairperson], Irish Atomistic Simulation Conference, Cork , 12-DEC-04 - 14-DEC-04. [Details]
(2001)Irish Atomistic Simulation Conference,
S.Fahy; (2001) Conference Organization. [Conference Organising Committee Chairperson], Irish Atomistic Simulation Conference, Cork , 12-DEC-01 - 14-DEC-01. [Details]
(1998)Irish Atomistic Simulation Conference,
S. Fahy; (1998) Conference Organization. [Conference Organising Committee Chairperson], Irish Atomistic Simulation Conference, Cork , 10-DEC-98 - 12-DEC-98. [Details]

Committees

 CommitteeFunctionFrom / To
Research Committee, Tyndall National Institute (Chair) Chair2007 /
Academic Council Research Committee, University College Cork (Chair, 2006-2009) Chair2006 / 2009
Scientific Council, Irish Centre for High-end Computing (Chair, 2005-2008) Chair (2005-2008)2005 /
Irish Atomistic Simulation Conference Coordinator1998 / 2007
Committee for Physics of Royal Irish Academy 2001 / 2004
European TMR Network Coordinator Coordinator1995 / 1997

Employment

 EmployerPositionFrom / To
Department of Physics / Tyndall Institute Associate Professor / Academic Member01-SEP-92 /
University of Michigan, USA Assistant Professor of Physics and Applied Physics01-AUG-90 / 01-MAY-93
AT&T Bell Laboratories, Murray Hill, USA Member of Technical Staff01-AUG-88 / 01-AUG-90
University of California, Berkeley Postdoctoral fellow01-JAN-87 / 01-JAN-88

Education

 YearInstitutionQualificationSubject
1987University of California, Berkeley PhDPhysics
1981University College Cork MScMathematics
1979University College Cork BScMathematical Science

Consultancy

 ClientDescription
Enterprise Ireland/Forbairt

Basic Science Grants Scheme 

Science Foundation Ireland

Research Frontiers Programme 2007

US National Science Foundation

: Reviewer for Division of Materials Research

Outreach Activities

 Description

SFI STARS Programme for Secondary School Teachers (2004-2005)

SFI UREKA Programme for undergraduate research experience (2004-2007)

Irish Primary Schools Outreach Programme - Bridging the Gap (2003-2005)

 Tyndall Sound Show - demonstration lecture for primary school students

 Sound Show, presented at the British Association Meeting, Dublin, 2005 

Journal Activities

 JournalRoleTo / From
Physical Review Letters Referee-
Physical Review B Referee-
Applied Physics Letters Referee-
Journal Of Physics A Referee-

Teaching Interests

My teaching interests are in general physics, condensed matter physics, theoretical & computational physics. Currently I am teaching:

Introductory Physics (PY1052 and PY1053) for physical and mathematical science majors

Condensed Matter Physics (PY3105 and PY4104)

Computational Physics (PY2105 and PY4109) 

INSPIRE graduate course on Numerical Methods