Interfacial Electron-Phonon Coupling and Quantum Confinement in Ultrathin Yb Films on Graphite

Publication

Author: Yi Wu, Wenhao Zhang, Yuan Fang, Shuai Lu, Li Wang, Peng Li, Zhongzheng Wu, Zhiguang Xiao, Chao Cao, Xiaoxiong Wang, Fang-Sen Li, Yi Yin, Tai-Chang Chiang, Yang Liu Physical Review B
URL: https://doi.org/10.1103/PhysRevB.104.L161402
Date: 2021 Instruments: ARPES Lab, DA30-L, VUV5k

Interfacial electron-phonon coupling in ultrathin films has attracted much interest recently. Here, by combining angle-resolved photoemission spectroscopy and scanning tunneling microscopy, we report quantized electronic states and strong interfacial electron-phonon coupling in ultrathin Yb films on graphite. We observed clear kinks in the energy-momentum dispersion of quantum well states, and the kink positions agree well with the energies of optical phonons of graphite. The extracted coupling strength λ is largest for the thinnest film with a preferred (“magic”) thickness of four monolayers and exhibits a strong band dependence, which can be qualitatively accounted for by a simple model. The interfacial electron-phonon coupling also gives rise to characteristic steplike structures in the dI/dV spectra, implying dominant coupling with the phonons with zero in-plane momentum. A Lifshitz transition occurs at higher coverage, where quantum well states derived mainly from 5d electrons dominate near the Fermi level and possess large effective mass (up to ∼19me). Our results highlight the potentially important role of interfacial electron-phonon interaction for ultrathin films and provide spectroscopic insight to understand this cross-interface fermion-boson interaction.

Interfacial Electron-Phonon Coupling and Quantum Confinement in Ultrathin Yb Films on Graphite

Publication

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