Honors & Awards


  • NDSEG Fellowship, Office of Naval Research (2015)
  • Stanford Graduate Fellowship, Stanford University (2015)
  • Goldwater Scholar, . (2014)

Education & Certifications


  • B.S., University of Pittsburgh, Physics with Honors (2015)

Lab Affiliations


All Publications


  • Band-Resolved Imaging of Photocurrent in a Topological Insulator PHYSICAL REVIEW LETTERS Soifer, H., Gauthier, A., Kemper, A. F., Rotundu, C. R., Yang, S., Xiong, H., Lu, D., Hashimoto, M., Kirchmann, P. S., Sobota, J. A., Shen, Z. 2019; 122 (16): 167401

    Abstract

    We study the microscopic origins of photocurrent generation in the topological insulator Bi_{2}Se_{3} via time- and angle-resolved photoemission spectroscopy. We image the unoccupied band structure as it evolves following a circularly polarized optical excitation and observe an asymmetric electron population in momentum space, which is the spectroscopic signature of a photocurrent. By analyzing the rise times of the population we identify which occupied and unoccupied electronic states are coupled by the optical excitation. We conclude that photocurrents can only be excited via resonant optical transitions coupling to spin-orbital textured states. Our work provides a microscopic understanding of how to control photocurrents in systems with spin-orbit coupling and broken inversion symmetry.

    View details for DOI 10.1103/PhysRevLett.122.167401

    View details for Web of Science ID 000466440000009

    View details for PubMedID 31075004

  • Femtosecond electron-phonon lock-in by photoemission and x-ray free-electron laser SCIENCE Gerber, S., Yang, S., Zhu, D., Soifer, H., Sobota, J. A., Rebec, S., Lee, J. J., Jia, T., Moritz, B., Jia, C., Gauthier, A., Li, Y., Leuenberger, D., Zhang, Y., Chaix, L., Li, W., Jang, H., Lee, J., Yi, M., Dakovski, G. L., Song, S., Glownia, J. M., Nelson, S., Kim, K. W., Chuang, Y., Hussain, Z., Moore, R. G., Devereaux, T. P., Lee, W., Kirchmann, P. S., Shen, Z. 2017; 357 (6346): 71–74

    Abstract

    The interactions that lead to the emergence of superconductivity in iron-based materials remain a subject of debate. It has been suggested that electron-electron correlations enhance electron-phonon coupling in iron selenide (FeSe) and related pnictides, but direct experimental verification has been lacking. Here we show that the electron-phonon coupling strength in FeSe can be quantified by combining two time-domain experiments into a "coherent lock-in" measurement in the terahertz regime. X-ray diffraction tracks the light-induced femtosecond coherent lattice motion at a single phonon frequency, and photoemission monitors the subsequent coherent changes in the electronic band structure. Comparison with theory reveals a strong enhancement of the coupling strength in FeSe owing to correlation effects. Given that the electron-phonon coupling affects superconductivity exponentially, this enhancement highlights the importance of the cooperative interplay between electron-electron and electron-phonon interactions.

    View details for PubMedID 28684521

  • Three-dimensional nature of the band structure of ZrTe5 measured by high-momentum-resolution photoemission spectroscopy PHYSICAL REVIEW B Xiong, H., Sobota, J. A., Yang, S., Soifer, H., Gauthier, A., Lu, M., Lv, Y., Yao, S., Lu, D., Hashimoto, M., Kirchmann, P. S., Chen, Y., Shen, Z. 2017; 95 (19)
  • Development and evaluation of a tutorial to improve students' understanding of a lock-in amplifier PHYSICAL REVIEW PHYSICS EDUCATION RESEARCH DeVore, S., Gauthier, A., Levy, J., Singh, C. 2016; 12 (2)
  • Improving student understanding of lock-in amplifiers AMERICAN JOURNAL OF PHYSICS DeVore, S., Gauthier, A., Levy, J., Singh, C. 2016; 84 (1): 52-56

    View details for DOI 10.1119/1.4934957

    View details for Web of Science ID 000367297900009