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Seminar
FIELD Computational Sciences
DATE September 17 (Fri), 2021
TIME 15:00-18:00
PLACE 1503
SPEAKER 김근수
HOST Son, Young-Woo
INSTITUTE 연세대
TITLE Pseudogap in a crystalline insulator doped by disordered metals
ABSTRACT

Two-dimensional (2D) quantum materials have continued to attract broad interest in the field of condensed-matter physics. One of the exciting opportunities with these materials is the tunable band structure with various “tuning knobs”, such as strain and electric field. The widely tunable band gap of black phosphorus [1] was used not only to deliberately induce the topological phase transition to the 2D Dirac semimetal [2], but to systematically trace the evolution of pseudospin (quantum phases) across band inversion [3]. In this talk, I will introduce our recent discovery of a pseudogap in black phosphorus doped by various alkali metals [4]. Using angle-resolved photoemission spectroscopy (ARPES), we reveal an anomalous band dispersion of back-bending and pseudogap, which can be explained by the Anderson-McMillan band dispersion of liquid metals proposed in the 1960s [5]. This is a natural consequence of resonance scattering by dopant ions with only short-range order (or liquid order). The depth of scattering potential tuned by different kinds of alkali metal (Na, K, Rb, and Cs) allows us to classify the pseudogap of p-wave and d-wave resonance.

References
1. J. Kim et al., Science 349, 723 (2015).
2. J. Kim et al., Phys. Rev. Lett. 119, 226801 (2017).
3. S. W. Jung, S. H. Ryu, W. J. Shin et al., Nature Mater. 19, 277 (2020).
4. S. H. Ryu, M. Huh, D. Y. Park et al., Nature 596, 68 (2021).
5. P. W. Anderson and W. L. McMillan, Multiple-Scattering Theory and Resonances in Transition Metals (Academic, New York, 1967).

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