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Alexander X. GrayAssistant Professor of PhysicsPh.D., University of California, Davis, 2011SERC, Room 442
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Research Interests
The ever-growing demand for miniaturization and increased speeds in next-generation energy-efficient electronic devices has taken science to the quantum frontier in which emergent phenomena at the nanoscale require a clear differentiation among surface, bulk and interface properties. Thus, for many technologically-promising novel materials, such as topological insulators, strongly-correlated oxides, and high-Tc superconductors, electronic structure and far-from-equilibrium dynamics vary dramatically as functions of depth and proximity to other materials. Therefore, novel depth-, time-, and spin-resolved element-specific characterization techniques are required to disentangle these rich electronic behaviors, including correlation effects, magnetism and spin. Inspired by these challenges, my research interests span two interrelated areas in experimental condensed matter physics: (1) depth-resolved spectroscopic imaging x-ray probes of electronic structure and (2) femtosecond electronic structure and spin dynamics. In particular, my research group is focusing on the development of new time-resolved FEL- and synchrotron-based x-ray techniques and applying these techniques to ultrafast depth-resolved studies of novel materials, buried interfaces, and multilayer structures.
Key Publications
R. U. Chandrasena, C. L. Flint, W. Yang, A. Arab, S. Nemšák, M. Gehlmann, V. B. Özdöl, F. Bisti, K. D. Wijesekara, J. Meyer-Ilse, E. Gullikson, E. Arenholz, J. Ciston, C. M. Schneider, V. N. Strocov, Y. Suzuki, and A. X. Gray, Depth-resolved charge reconstruction at the LaNiO3/CaMnO3 interface, Phys. Rev. B 98, 155103 (2018). [link]
A. X. Gray et al., Ultrafast THz Field Control of Electronic and Structural Interactions in Vanadium Dioxide, Phys. Rev. B 98, 045104 (2018). [link]
M. Golalikhani, Q. Lei, R. U. Chandrasena, L. Kasaei, H. Park, J. Bai, P. Orgiani, J. Ciston, G. Sterbinsky, D. A. Arena, P. Shafer, E. Arenholz, B. Davidson, A. J. Millis, A. X. Gray, and X. X. Xi, Nature of the metal-insulator transition in few-unit-cells-thick LaNiO3 films, Nature Comm. 9, 2206 (2018). [link]
R. U. Chandrasena, W. Yang, Q. Y. Lei, M. U. Delgado-Jaime, K. Wijesekara, M. Golalikhani, B. A. Davidson, E. Arenholz, K. Kobayashi, M. Kobata, F. M. F. de Groot, U. Aschauer, N. A. Spaldin, X. X. Xi, and A. X. Gray, Strain-Engineered Oxygen Vacancies in CaMnO3 Thin Films, Nano Letters 17, 794 (2017). [link]
A. X. Gray et al., Correlation-Driven Insulator-Metal Transition in Near-Ideal Vanadium Dioxide Films, Phys. Rev. Lett. 116, 116403 (2016). [link]
A. X. Gray et al., Probing Bulk Electronic Structure with Hard X-Ray Angle-Resolved Photoemission, Nature Materials 10, 759 (2011). [link]
A. X. Gray et al., Bulk Electronic Structure of the Dilute Ferromagnetic Semiconductor Ga1-xMnxAs through Hard X-ray Angle-Resolved Photoemission, Nature Materials 11, 957 (2012). [link]
A. X. Gray et al., Electronic Structure Changes across the Metamagnetic Transition in FeRh via Hard X-ray Photoemission, Phys. Rev. Lett. 108, 257208 (2012). [link]
N. B. Aetukuri, A. X. Gray et al., Control of the Metal-Insulator Transition in Vanadium Dioxide by Modifying Orbital Occupancy, Nature Physics 9, 661 (2013). [link]
A. X. Gray et al., Momentum-Resolved Electronic Structure at a Buried Interface from Soft X-ray Standing-Wave Angle-Resolved Photoemission, Europhys. Lett. 104, 17004 (2013). [link]
A. X. Gray, Future Directions in Standing-Wave Photoemission, J. Electron Spectrosc. Relat. Phenom. 195, 399 (2014). [link]
A. X. Gray et al., Interface Properties of Magnetic Tunnel Junction LSMO/STO Superlattices Studied by Standing-Wave Excited Photoemission Spectroscopy, Phys. Rev. B 82, 205116 (2010). [link]
A. X. Gray et al., Standing-Wave Excited Soft X-Ray Photoemission Microscopy: Application to Co Microdot Magnetic Arrays, Appl. Phys. Lett. 97, 062503 (2010). [link]
A. M. Kaiser, A. X. Gray et al., Suppression of Near-Interface Electronic States at the Fermi Level of LaNiO3/SrTiO3 Superlattices, Phys. Rev. Lett. 107, 116402 (2011). [link]
S. X-L. Sun, A. P. Kaduwela, A. X. Gray, and C. S. Fadley, Progress Toward Time-Resolved Molecular Imaging: a Theoretical Study of Optimal Parameters in Static Photoelectron Holography, Phys. Rev. A 89, 053415 (2014). [link]
A. X. Gray et al., Ultrafast THz Field Control of Electronic and Structural Interactions in Vanadium Dioxide, Phys. Rev. B 98, 045104 (2018). [link]
M. Golalikhani, Q. Lei, R. U. Chandrasena, L. Kasaei, H. Park, J. Bai, P. Orgiani, J. Ciston, G. Sterbinsky, D. A. Arena, P. Shafer, E. Arenholz, B. Davidson, A. J. Millis, A. X. Gray, and X. X. Xi, Nature of the metal-insulator transition in few-unit-cells-thick LaNiO3 films, Nature Comm. 9, 2206 (2018). [link]
R. U. Chandrasena, W. Yang, Q. Y. Lei, M. U. Delgado-Jaime, K. Wijesekara, M. Golalikhani, B. A. Davidson, E. Arenholz, K. Kobayashi, M. Kobata, F. M. F. de Groot, U. Aschauer, N. A. Spaldin, X. X. Xi, and A. X. Gray, Strain-Engineered Oxygen Vacancies in CaMnO3 Thin Films, Nano Letters 17, 794 (2017). [link]
A. X. Gray et al., Correlation-Driven Insulator-Metal Transition in Near-Ideal Vanadium Dioxide Films, Phys. Rev. Lett. 116, 116403 (2016). [link]
A. X. Gray et al., Probing Bulk Electronic Structure with Hard X-Ray Angle-Resolved Photoemission, Nature Materials 10, 759 (2011). [link]
A. X. Gray et al., Bulk Electronic Structure of the Dilute Ferromagnetic Semiconductor Ga1-xMnxAs through Hard X-ray Angle-Resolved Photoemission, Nature Materials 11, 957 (2012). [link]
A. X. Gray et al., Electronic Structure Changes across the Metamagnetic Transition in FeRh via Hard X-ray Photoemission, Phys. Rev. Lett. 108, 257208 (2012). [link]
N. B. Aetukuri, A. X. Gray et al., Control of the Metal-Insulator Transition in Vanadium Dioxide by Modifying Orbital Occupancy, Nature Physics 9, 661 (2013). [link]
A. X. Gray et al., Momentum-Resolved Electronic Structure at a Buried Interface from Soft X-ray Standing-Wave Angle-Resolved Photoemission, Europhys. Lett. 104, 17004 (2013). [link]
A. X. Gray, Future Directions in Standing-Wave Photoemission, J. Electron Spectrosc. Relat. Phenom. 195, 399 (2014). [link]
A. X. Gray et al., Interface Properties of Magnetic Tunnel Junction LSMO/STO Superlattices Studied by Standing-Wave Excited Photoemission Spectroscopy, Phys. Rev. B 82, 205116 (2010). [link]
A. X. Gray et al., Standing-Wave Excited Soft X-Ray Photoemission Microscopy: Application to Co Microdot Magnetic Arrays, Appl. Phys. Lett. 97, 062503 (2010). [link]
A. M. Kaiser, A. X. Gray et al., Suppression of Near-Interface Electronic States at the Fermi Level of LaNiO3/SrTiO3 Superlattices, Phys. Rev. Lett. 107, 116402 (2011). [link]
S. X-L. Sun, A. P. Kaduwela, A. X. Gray, and C. S. Fadley, Progress Toward Time-Resolved Molecular Imaging: a Theoretical Study of Optimal Parameters in Static Photoelectron Holography, Phys. Rev. A 89, 053415 (2014). [link]
Book Chapters
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A. X. Gray, Hard X-ray Angle-Resolved Photoelectron Spectroscopy (HARPES), invited chapter in the book Hard X-ray Photoelectron Spectroscopy (HAXPES), J. Woicik, Ed. (Springer, 2016).
S. Nemsak, A. X. Gray, and C. S. Fadley, Standing-Wave and Resonant Soft- and Hard- X-Ray Photoelectron Spectroscopy of Oxide Interfaces, invited chapter in the book Spectroscopy of Transition-Metal Oxide Interfaces, C. Cancellieri and V. N. Strocov, Eds. (Springer, 2018).
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