Ultrathin Bismuth Film on 1T-TaS<sub>2</sub>: Structural Transition and Charge-Density-Wave Proximity Effect.

Yamada, Keiko; Souma, Seigo; Yamauchi, Kunihiko; Shimamura, Natsumi; Sugawara, Katsuaki; Trang, Chi Xuan; Oguchi, Tamio; Ueno, Keiji et al. · Nano Lett · 2018

basic_science · Level V

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Abstract

We have fabricated bismuth (Bi) ultrathin films on a charge-density-wave (CDW) compound 1T-TaS<sub>2</sub> and elucidated electronic states by angle-resolved photoemission spectroscopy and first-principles band-structure calculations. We found that the Bi film on 1T-TaS<sub>2</sub> undergoes a structural transition from (111) to (110) upon reducing the film thickness, accompanied by a drastic change in the energy band structure. We also revealed that while two-bilayer-thick Bi(110) film on Si(111) is characterized by a dispersive band touching the Fermi level ( E<sub>F</sub>), the energy band of the same film on 1T-TaS<sub>2</sub> exhibits holelike dispersion with a finite energy gap at E<sub>F</sub>. We discuss the origin of such intriguing differences in terms of the CDW proximity effect.