Anomalous Phonon Behavior and Tunable Exciton Emissions: Insights into Pressure-Driven Dynamics in Silicon Phosphide.

Xie, Xing; Ding, Junnan; Wu, Biao; Li, Shaofei; Chen, Junying; He, Jun; Liu, Zongwen; Wang, Jian-Tao et al. · Nano Lett · 2024

basic_science · Level V

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Abstract

IV-V two-dimensional materials have emerged as key contenders for polarization-sensitive and angle-resolved devices, given their inherent anisotropic physical properties. While these materials exhibit intriguing high-pressure quasi-particle behavior and phase transition, the evolution of quasi-particles and their interactions under external pressure remain elusive. Here, employing a diamond anvil cell and spectroscopic measurements coupled with first-principles calculations, we unveil rarely observed pressure-induced phonon-phonon coupling in layered SiP flakes. This coupling manifests as an anomalous phonon hardening behavior for the A<sub>1</sub> mode within a broad wavenumber phonon softening region. Furthermore, we demonstrate the effective tuning of exciton emissions in SiP flakes under pressure, revealing a remarkable 63% enhancement in the degree of polarization (DOP) within the pressure range of 0-3.5 GPa. These findings contribute to our understanding of high-pressure phonon evolution in SiP materials and offer a strategic approach to manipulate the anisotropic performance of in-plane anisotropic 2D materials.