|DATE||October 01 (Fri), 2021|
|SPEAKER||Jung, Su Yong|
|TITLE||Electron tunneling spectroscopy studies on electron–phonon couplings in semiconducting and superconducting transition metal dichalcogenides|
Electron tunneling spectroscopies are versatile experimental methods to investigate not just detailed electronic structures of low-dimensional condensed matter systems at varying energies but also collective excitations such as phonons, magnons and plasmons and their interactions with electrons. In particular, it has proven that planar tunnel junctions that employ two-dimensional (2D) insulators like hexagonal boron nitride or wide energy- gap semiconductors such as WSe2 and MoSe2 enhance spectral resolutions of tunnel electrons in energy while varying external electric and magnetic fields, charge densities, temperatures, and others. In this talk, I will present electron tunneling spectroscopy measurements on vertically assembled van der Waals tunnel junctions of semiconducting films of WSe2, MoSe2, WS2 and MoS2 and superconducting layers of NbSe2. Through detailed electron tunneling spectroscopy measurements, phonon-mode specific electron– phonon scattering processes in the 2D semiconductors are experimentally verified. In addition, I will discuss a couple of intriguing spectral features that can be related to charge- density wave and electron–phonon couplings in the 2D superconducting NbSe2 layers.