New polymorphic phase and rich phase diagram in the PdSe2-xTex system

TL;DR

This study explores the structural and electronic phase transitions in the PdSe2-xTex system, revealing a new monoclinic phase, diverse structural phases, and enhanced superconductivity within specific Te compositions, combining experimental and theoretical insights.

Contribution

The paper reports the discovery of a new monoclinic polymorphic phase in PdSe2-xTex and maps its rich phase diagram with detailed electronic and transport properties, advancing understanding of transition metal dichalcogenides.

Findings

Identification of a new monoclinic phase (C2/c) in PdSe2-xTex.

Observation of superconductivity with increased critical temperature in the trigonal phase.

Detailed structural evolution from orthorhombic to monoclinic to trigonal phases.

Abstract

We report a combined experimental and theoretical study of the PdSe2-xTex system. With increasing Te fraction, structural evolutions, first from an orthorhombic phase (space group Pbca) to a monoclinic phase (space group C2/c) and then to a trigonal phase (space group P-3m1), are observed accompanied with clearly distinct electrical transport behavior. The monoclinic phase (C2/c) is a completely new polymorphic phase and is discovered within a narrow range of Te composition (0.3 \leq x \leq 0.8). This phase has a different packing sequence from all known transition metal dichalcogenides to date. Electronic calculations and detailed transport analysis of the new polymorphic PdSe1.3Te0.7 phase are presented. In the trigonal phase region, superconductivity with enhanced critical temperature is also observed within a narrow range of Te content (1.0 \leq x \leq 1.2). The rich phase diagram, new polymorphic structure as well as abnormally enhanced superconductivity could further stimulate more interest to explore new types of polymorphs and investigate their transport and electronic properties in the transition metal dichalcogenides family that are of significant interest.