ABSTRACT
The physics of high-temperature superconductors is governed by the interplay of spin and charge degrees of freedom. Despite its simple chemical composition, monolayer FeSe on a SrTiO3 substrate exhibits one of the highest superconducting transition temperatures, exceeding that of bulk FeSe. We investigate the various factors contributing to this enhancement, including charge transfer, spin magnetic moment, and phonon coupling.
For example, a key observation of monolayer FeSe is the presence of replica bands in the photoemission spectrum, believed to be evidence of strong electron-phonon interaction. However, the exact nature of these bands remains disputed. To gain new insights into this phenomenon, we conducted angle-resolved photoemission spectroscopy measurements on monolayer FeSe/SrTiO3 using linearly polarized photons. Our results revealed high-order replica bands derived from various Fe 3d bands, similar to those observed on bare SrTiO3.
Overall, our findings provide valuable insights into the mechanisms underlying the enhanced superconductivity observed in monolayer FeSe, and shed new light on the role of charge transfer, spin magnetic moment, and phonon coupling.
References
1. C. Liu, H. Shin, A. Doll, H.H. Kung, R.P. Day, B.A. Davidson, J. Dreser, G. Levy, A. Damascelli, C. Piamonteze, and K. Zou, “High-temperature superconductivity and robustness against magnetic polarization in monolayer FeSe on EuTiO3”, npj Quantum Materials 6, 85 (2021).
2. C. Liu, R.P. Day, F. Li, R.L. Roemer, S. Zhdanovich, S. Gorovikov, T. Pedersen, J. Jiang, S. Lee, M. Schneider, D. Wong, P. Dosanjh, F.J. Walker, C.H. Ahn, G. Levy, A. Damascelli, G.A. Sawatzky, and K. Zou, “High-order replica bands in monolayer FeSe/SrTiO3 revealed by polarization-dependent photoemission spectroscopy”, Nature Communications 12, 4573 (2021).
3. R. Peng, K. Zou, M. G. Han, S.D. Albright, H. Hong, C. Lau, H. C. Xu, Y. Zhu, F.J. Walker, C.H. Ahn, “Picoscale structural insight into superconductivity of monolayer FeSe/SrTiO3”, Science Advances 6, eaay4517 (2020).
BIOGRAPHY
Prof. Ke Zou is currently an Assistant Professor in the Department of Physics and Astronomy and a Principal Investigator at the Quantum Matter Institute (QMI) of the University of British Columbia (UBC). Prior to this, he was a Postdoctoral Associate at the Department of Applied Physics at Yale University. Prof. Zou has published 38 research papers and has been cited above 2,400 times, with an h-index of 18, according to Google Scholar. At UBC, he established a molecular beam epitaxy (MBE) synthesis laboratory, which provides unique infrastructure for material and device development, with the aim of achieving scientific and technological breakthroughs utilizing various materials at the nanoscale. Prof. Zou's research combines MBE synthesis with nanostructure fabrication and characterization techniques to investigate and control the physical and electronic properties of new thin film materials.
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