A real-time TDDFT study of femtosecond laser driven monolayer NbSe2

TL;DR

This study uses real-time TDDFT to analyze how femtosecond laser pulses induce high harmonic generation in monolayer NbSe2, revealing signatures of charge density wave order and its potential for controlling quantum phases.

Contribution

It provides the first computational prediction of HHG signatures associated with CDW order in monolayer NbSe2 under ultrafast laser excitation.

Findings

Distinct HHG spectral signatures indicate CDW presence.

HHG spectra depend on excitation intensity.

Power-law behavior observed in HHG response.

Abstract

High harmonic generation (HHG) spectra have the potential to show novel signatures of ordered phases in condensed matter. We studied the femtosecond laser-driven electronic response of monolayer NbSe2 using state-of-the-art computational methods, which can guide future synthesis and optical characterization. Earlier studies found distinct signatures of charge density wave (CDW) ordered phases in the ground state of NbSe2 monolayers, in co-existence with superconductivity. Driving such systems with ultrashort laser pulses can shed new light on optically controlling various exotic phases (e.g. CDW) in monolayer NbSe2. This will not only provide a fundamental understanding of non-equilibrium phase-transitions in NbSe2, but also will open a path forward for revolutionizing quantum information technologies, such as valleytronics. To this end, we have studied high harmonic generation (HHG) in monolayer NbSe2 under various optical pump intensities using real-time time-dependent density functional theory (RT-TDDFT). Our calculations predict distinct signatures in HHG spectra for certain harmonics in the presence of CDW order in monolayer NbSe2. Finally, we also examined the dependence of HHG spectra on excitation intensity and qualitatively revealed its power-law behavior.