Study On Lattice Vibration Properties Of Monolayer 1T’-WTe₂ In Response To Charge Doping

Charge doping is an effective means to control the monolayer 1T’-WTe2 as a topological superconductor.This not only provides a good quantum platform for the study of Majorana fermions,but also provides feasible solutions for the development of single-material quantum computers.As the energons of lattice vibrations,phonons can not only couple with electrons to form superconducting state,but also undergo inelastic scattering with the photons to produce Raman spectrum.Therefore,the systematic study of the lattice vibration characteristics of doped 1T’-WTe2 is of great theoretical significance and application value for understanding the superconducting origin or Raman frequency-shift of 1T’-WTe2.In this thesis,by using the first-principles calculation,We systematically investigate the evolution of lattice vibration spectra of monolayer 1T’-WTe2 under hole doping and electron doping.Research findings are as below:1.The phonon mode of monolayer 1T’-WTe2 softens only upon electron doping,but not upon hole doping.And the soft mode mediates the electron-phonon coupling of electron-doped WTe2 to form a superconducting state,but not for the hole-doped WTe2.This conclusion explains very well the two experimental works published in the Science.2.The Raman-active modes of the monolayer 1T’-WTe2 vary differently with the doping concentration,and a detail analysis is given by combining the vibration characteristics of Raman-active modes,the charge difference density and the orbital occupation of doped charges.This points out a new way for experimentally monitoring the doping level of WTe2-based electronics according to the frequency-shift of the Raman spectrum.