Transport anomalies in the layered compound BaPt4Se6

TL;DR

This study investigates the layered compound BaPt4Se6, revealing transport anomalies, a hidden low-temperature state, and a stable metallic electronic structure without structural phase transitions.

Contribution

It uncovers unique transport anomalies and a hidden low-temperature state in BaPt4Se6, expanding understanding of layered selenides with mixed-valence platinum.

Findings

Resistivity crossover near 150K resembling metal-insulator transition

Resistivity plateau observed below 10K indicating a hidden state

No structural or magnetic phase transition detected up to 200K

Abstract

We report a layered ternary selenide BaPt4Se6 featuring sesqui-selenide Pt2Se3 layers sandwiched by Ba atoms. The Pt2Se3 layers in this compound can be derived from the Dirac-semimetal PtSe2 phase with Se vacancies that form a honeycomb structure. This structure results in a Pt (VI) and Pt (II) mixed-valence compound with both PtSe6 octahedra and PtSe4 square net coordination configurations. Temperature dependent electrical transport measurements suggest two distinct anomalies: a resistivity crossover, mimic to the metal-insulator (M-I) transition at ~150K, and a resistivity plateau at temperatures below 10K. The resistivity crossover is not associated with any structural, magnetic or charge order modulated phase transitions. Magnetoresistivity, Hall and heat capacity measurements concurrently suggest an existing hidden state below 5K in this system. Angle-resolved photoemission spectroscopy measurements reveal a metallic state and no dramatic reconstruction of the electronic structure up to 200K.