Optical study of phase transitions in single-crystalline RuP

TL;DR

This study investigates the structural, electronic, and optical properties of single-crystalline RuP, revealing two phase transitions with significant band structure changes and a charge-density-wave gap, contrasting with polycrystalline behavior.

Contribution

It provides new insights into the phase transitions of RuP through combined structural, resistivity, magnetic, and optical measurements on single crystals.

Findings

Two structural phase transitions confirmed by x-ray diffraction.

Metallic behavior observed below the second transition, unlike polycrystals.

Band structure reconstruction and charge-density-wave gap opening detected via optical conductivity.

Abstract

RuP single crystals of MnP-type orthorhombic structure were synthesized by the Sn flux method. Temperature-dependent x-ray diffraction measurements reveal that the compound experiences two structural phase transitions, which are further confirmed by enormous anomalies shown in temperature-dependent resistivity and magnetic susceptibility. Particularly, the resistivity drops monotonically upon temperature cooling below the second transition, indicating that the material shows metallic behavior, in sharp contrast with the insulating ground state of polycrystalline samples. Optical conductivity measurements were also performed in order to unravel the mechanism of these two transitions. The measurement revealed a sudden reconstruction of band structure over a broad energy scale and a significant removal of conducting carriers below the first phase transition, while a charge-density-wave-like energy gap opens below the second phase transition.