Resonant quenching of Raman scattering due to out-of-plane A$_{1g}$/A'$_1$ modes in few-layer MoTe$_2$

TL;DR

This study investigates temperature-dependent Raman scattering in few-layer MoTe₂, revealing resonant quenching effects in out-of-plane phonon modes due to interference between resonant and non-resonant scattering contributions, with implications for understanding electronic-phonon interactions.

Contribution

It demonstrates the temperature-dependent resonant quenching of Raman modes in few-layer MoTe₂, highlighting interference effects linked to electronic excitations at the M point.

Findings

Non-monotonic temperature dependence of Raman mode intensity.

Complete vanishing and recovery of A₁g mode intensity in 2L MoTe₂.

Resonant quenching attributed to interference at the M point.

Abstract

Temperature-dependent (5 K to 300 K) Raman scattering study of A$_{1g}$/A'$_1$ phonon modes in mono-layer (1L), bilayer (2L), trilayer (3L), and tetralayer (4L) MoTe$_2$ is reported. The temperature evolution of the modes' intensity critically depends on the flake thickness. In particular with $\lambda$=632.8 nm light excitation, a strongly non-monotonic dependence of the A$_{1g}$ mode intensity is observed in 2L MoTe$_2$. The intensity decreases with decreasing temperature down to 220 K and the A$_{1g}$ mode almost completely vanishes from the Stokes scattering spectrum in the temperature range between 160 K and 220 K. The peak recovers at lower temperatures and at T=5 K it becomes three times more intense that at room temperature. Similar non-monotonic intensity evolution is observed for the out-of-plane mode in 3L MoTe$_2$ in which tellurium atoms in all three layers vibrate in-phase. The intensity of the other out-of-plane Raman-active mode, (with vibrations of tellurium atoms in the central layer shifted by 180$^o$ with respect to the vibrations in outer layers), only weakly depends on temperature. The observed quenching of the Raman scattering in 2L and 3L MoTe$_2$ is attributed to a destructive interference between the resonant and non-resonant contributions to the Raman scattering amplitude. The observed "antiresonance" is related to the electronic excitation at the M point of the Brillouin zone in few-layer MoTe$_2$.