Dimensional crossover and emergence of novel phases in puckered PdSe$_2$ under pressure

TL;DR

This study explores how applying pressure to PdSe₂ causes structural and electronic phase transitions, including a dimensional crossover from 2D to 3D, leading to novel phases and potential superconductivity.

Contribution

It reveals pressure-induced structural and electronic transitions in PdSe₂, including a dimensional crossover and emergence of new phases, advancing understanding of pressure effects in puckered layered materials.

Findings

Suppression of Jahn-Teller distortion at 2.3 GPa causes lattice expansion and metallization.

At 4.8 GPa, a dimensional crossover from 2D to 3D occurs via orbital hybridization.

A new high-pressure phase with octahedral distortions emerges around 9 GPa, linked to superconductivity.

Abstract

We investigate the pressure-driven structural and electronic evolution of PdSe\(_2\) using powder X-ray diffraction, Raman spectroscopy, and first-principles calculations. Beyond 2.3 GPa, suppression of the Jahn-Teller distortion induces in-plane lattice expansion and metallization. Around 4.8 GPa, the interlayer \(d_{z^2}-\pi^*\) orbital hybridization drives the dimensional crossover, facilitating the transformation from the 2D distorted to a 3D undistorted pyrite phase. At $\sim$ 9 GPa, a novel phase emerges, characterized by octahedral distortions in the $d$ orbitals of Pd. Structural analysis suggests the presence of marcasite (\(Pnnm\)) or arsenopyrite (\(P2_1/c\)) phase with orthorhombic and monoclinic configurations, respectively. Furthermore, the observed phonon anomaly and electronic structure modifications, including the emergence of flat bands in the high-pressure phases, elucidate the fundamental mechanisms underlying the previously reported exotic superconductivity with an enhanced critical temperature. These results highlight the pivotal role of dimensional crossover and structural transitions in tuning the electronic properties of puckered materials, providing pathways for novel functionalities.