Phonon-assisted electronic states modulation of few-layer PdSe2 at terahertz frequencies

TL;DR

This paper demonstrates how femtosecond laser-driven phonons can coherently manipulate electronic states in layered PdSe2 at terahertz frequencies, advancing high-speed optoelectronic device potential.

Contribution

It introduces a method to control excitonic properties in 2D materials using phonons at THz frequencies, combining ultralow frequency Raman spectroscopy with first-principles calculations.

Findings

Identification of phonon mode-selective electron-phonon interactions

Coupling of intralayer phonons to carriers and interlayer phonons to excitons

Potential for high-speed THz optoelectronic applications

Abstract

Information technology demands high-speed optoelectronic devices, but going beyond the one terahertz (THz) barrier is challenging due to the difficulties associated with generating, detecting, and processing high-frequency signals. Here, we show that femtosecond-laser-driven phonons can be utilized to coherently manipulate the excitonic properties of semiconductors at THz frequencies. The precise control of the pump and subsequent time-delayed broadband probe pulses enables the simultaneous generation and detection processes of both periodic lattice vibrations and their couplings with electronic states. Combining ultralow frequency Raman spectroscopy with first-principles calculations, we identify the unique phonon mode-selective and probe-energy dependent features of electron-phonon interactions in layered PdSe2. Two distinctive types of coherent phonon excitations could couple preferentially to different types of electronic excitations: the intralayer (4.3 THz) mode to carriers and the interlayer (0.35 THz) mode to excitons. This work provides new insights to understand the excited-state phonon interactions of 2D materials, and to achieve future applications of optoelectronic devices operating at THz frequencies.