Pressure-induced structural phase transition and new superconducting phase in UTe2

TL;DR

This study explores how high pressure induces structural phase transitions in UTe2, leading to a new superconducting phase above 7 GPa, with significant changes in electronic states and crystal structure.

Contribution

It provides the first detailed high-pressure structural and electronic characterization of UTe2, revealing a pressure-induced phase transition and emergence of a new superconducting phase.

Findings

Structural phase transition from orthorhombic to tetragonal above 3.5-4 GPa.

Detection of a new superconducting phase above 7 GPa with Tsc > 2K.

Significant electronic state change from heavy fermion to weakly correlated states.

Abstract

We report on the crystal structure and electronic properties of the heavy fermion superconductor UTe2 at high pressure up to 11 GPa, as investigated by X-ray diffraction and electrical resistivity experiments. The X-ray diffraction measurements under high pressure using a synchrotron light source reveal anisotropic linear compressibility of the unit cell up to 3.5 GPa, while a pressure-induced structural phase transition is observed above 3.5-4GPa at room temperature, where the body-centered orthorhombic crystal structure with the space group Immm changes into a body-centered tetragonal structure with the space group I4/mmm. The molar volume drops abruptly at the critical pressure, while the distance between the first-nearest neighbor of U atoms increases, implying a switch from the heavy electronic states to the weakly correlated electronic states. Surprisingly, a new superconducting phase at pressures higher than 7 GPa was detected at Tsc above 2K with a relatively low upper-critical field, Hc2(0). The resistivity above 3.5GPa, thus, in the high-pressure tetragonal phase, shows a large drop below 230 K, which may also be related to a considerable change from the heavy electronic states to the weakly correlated electronic states.