Pump-triple sum-frequency-probe spectroscopy of transition metal dichalcogenides

TL;DR

This paper introduces pump-TSF-probe spectroscopy as a novel method for studying transition metal dichalcogenides, demonstrating its advantages over traditional techniques in sensitivity and applicability to various nanostructures.

Contribution

The work presents the first application of pump-TSF-probe spectroscopy to transition metal dichalcogenides, showing its effectiveness and independence from sample coverage and morphology.

Findings

Pump-TSF-probe spectra are similar to transient-reflectance spectra.

Pump-TSF-probe sensitivity is unaffected by surface coverage.

Method is effective on various nanostructures of MoS2 and WS2.

Abstract

Triple sum-frequency (TSF) spectroscopy measures multidimensional spectra by resonantly exciting multiple quantum coherences of vibrational and electronic states. In this work we demonstrate pump-TSF-probe spectroscopy in which a pump excites a sample and some time later three additional electric fields generate a probe field which is measured. We demonstrate pump-TSF-probe spectroscopy on polycrystalline, smooth, thin films and spiral nanostructures of both MoS2 and WS2. The pump-TSF-probe spectra are qualitatively similar to the more conventional transient-reflectance spectra. While transient-reflectance sensitivity suffers under low surface coverage, pump-TSF-probe sensitivity is independent of the sample coverage and nanostructure morphologies. Our results demonstrate that pump-TSF-probe is a valuable methodology for studying microscopic material systems.