Probing anharmonic phonons in WS van der Waals crystal by Raman spectroscopy and machine learning.

Understanding the optothermal physics of quantum materials will enable the efficient design of next-generation photonic and superconducting circuits. Anharmonic phonon dynamics is central to strongly interacting optothermal physics. This is because the pressure of a gas of anharmonic phonons is temperature dependent. Phonon-phonon and electron-phonon quantum interactions contribute to the anharmonic phonon effect. Here we have studied the optothermal properties of physically exfoliated WS van der Waals crystal via temperature-dependent Raman spectroscopy and machine learning strategies. This fundamental investigation will lead to unveiling the dependence of temperature on in-plane and out-of-plane Raman shifts (Raman thermometry) of WS to study the thermal conductivity, hot carrier diffusion coefficient, and thermal expansion coefficient.