Response of Raman-active modes in monolayer 1T\'-WTe2 to charge doping

• 1、School of Electronic Engineering, Beijing University of Posts and Telecommunications, Beijing, 100876

Abstract：Monolayer 1T\'-WTe2 has been tuned to be superconducting by electrostatic gating in recent experiments, which has been explained by soft-mode-phonon-mediated superconductivity in theory. In addition to the phonon branch softening, the charge doping would also affect the Raman vibration properties of monolayer 1T\'-WTe2. In this paper, by using the first-principles calculation, we investigate the response of Raman-active modes in monolayer 1T\'-WTe2 to charge doping systematically. It is found that, when doped with electrons, most of the Raman modes are blue-shifted, and when doped with holes, most of the Raman modes are red-shifted. Anomalously, Ag2, Ag3 and Bg3 modes decrease in frequency with the increasing doping concentration, and Ag3 and Ag6 modes have frequency changes with multiple turning points. The frequency of Ag3 mode, especially, varies in a "M" type with increasing doping concentration, which is correlated with the out-of-plane vibrational properties of the Te atoms. The other two vibration modes corresponding to the Raman spectral peaks, Ag1 and Ag4 modes, whose frequencies vary linearly with the doping concentration. This is important for understanding the Raman spectra of doped WTe2 as well as for monitoring the doping levels in WTe2-based electronic devices with a frequency-shift for Raman spectral peaks.

Keywords： condensed matter physics monolayer 1T\'-WTe2 Raman-active modes charge doping