Photoacoustic detection of phase transitions at low temperatures in CsPbCl$_3$ crystals

TL;DR

This study uses photoacoustic methods to detect and analyze phase transitions in CsPbCl$_3$ crystals at low temperatures, revealing two phase transitions around 200 K through ultrasonic wave analysis.

Contribution

The paper introduces a photoacoustic technique combined with wavelet analysis to identify phase transitions in CsPbCl$_3$ crystals at low temperatures, providing new insights into their thermoelastic properties.

Findings

Identification of two phase transitions near 200 K.

Detection of MHz components in thermoelastic ultrasonic waves.

Correlation of PA signals with phase transition phenomena.

Abstract

Phase transitions in CsPbCl$_3$ crystals have been explored by photoacoustic (PA) method in a wide temperature range of 150--300 K. The PA signals, induced by ns-pulsed laser excitation of electronic states and detected with a piezoelectric transducer, are thermoelastic ultrasonic waves lasting for hundreds of microseconds. The wavelet analysis of the PA wave has clarified that the thermoelastic wave includes several MHz components. The PA signals have been made use of in order to examine phase transitions at low temperatures in the crystal. Changes of PA signals indicate that two phase transitions take place at low temperatures around 200 K. The types of phase transitions are discussed taking into recent experimatal results.