Terahertz Kerr effect in a methylammonium lead bromide perovskite crystal

TL;DR

This study observes and analyzes the ultrafast terahertz Kerr effect in a methylammonium lead bromide perovskite crystal, revealing complex lattice and molecular dynamics induced by terahertz pulses.

Contribution

It provides the first detailed characterization of the terahertz Kerr effect and associated ultrafast dynamics in methylammonium lead bromide perovskite crystals.

Findings

Detection of short-lived optical birefringence induced by terahertz pulses

Identification of multiple decay and oscillation components in the anisotropy signal

Attribution of features to lattice Kerr effect, cation alignment, and coherent rotation

Abstract

We have observed short-lived optical birefringence in a CH$_3$NH$_3$PbBr$_3$ single crystal induced by a powerful nearly single-cycle terahertz pulse. Apart from the instantaneous contribution that follows the profile of the squared pump electric field, the recorded anisotropy signal contains an exponential component decaying in $\sim$ 350 fs, underdamped oscillations at the frequency of $\sim$ 0.16 THz and an intermediate picosecond relaxation process with a Gaussian tail. We associate these three non-trivial features with, respectively, Kerr effect in the inorganic lattice, terahertz-induced transient alignment of CH$_3$NH$_3^+$ cations, and their coherent rotation excited by the terahertz pulse in a Raman process.