Metastable phase of UTe${}_2$ formed under high pressure above 5 GPa

Abstract

Uranium ditelluride (UTe${}_2$) has attracted recent interest due to its unique superconducting properties, which include the potential for a topological odd-parity superconducting state. Recently, ac-calorimetry measurements under pressure indicate a change in the ground state of UTe${}_2$ from superconducting to antiferromagnetic at 1.4 GPa. Here, we investigate the effect of pressure on the crystal structure of UTe${}_2$ up to 25 GPa at room temperature using x-ray diffraction. We find that UTe${}_2$, which at ambient conditions has an orthorhombic ($Immm$) structure, transforms to a body-centered tetragonal ($I4/mmm$) structure at 5 GPa in a quasi-hydrostatic neon (Ne) pressure transmitting medium. In the absence of a pressure-transmitting medium, this transformation occurs between 5 and 8 GPa. The data were fit with a third-order Birch-Murnaghan equation of state resulting in values of $B_0$=46.0 $\pm$ 0.6 GPa, $B^{\prime }$=9.3 $\pm$ 0.5 (no pressure medium) and $B_0$=42.5 $\pm$ 2.0 GPa, $B^{\prime }$=9.3 (fixed) (neon pressure medium) for the $Immm$ phase. For the $I4/mmm$ phase, $B_0$=78.9 $\pm$ 0.5 GPa and $B^{\prime }$=4.2 $\pm$ 0.1 (no pressure transmitting medium), and $B_0$=70.0 $\pm$ 1.1 GPa and $B^{\prime }$=4.1 $\pm$ 0.2 (neon pressure medium). The high-pressure tetragonal phase is retained after decompression to ambient pressure, with approximately 30% remaining after 2 days. We argue that the observed phase transition into a higher symmetry structure at P~5 GPa (orthorhombic to tetragonal), is accompanied by an increase in the shortest distance between uranium atoms from 3.6 Angstrom (orthorhombic) to 3.9 Angstrom (tetragonal), which suggests localization of the 5f electrons, albeit with a 10.7% decrease in volume.

Includes supplemental material

References in corpus (5)

• Unconventional Superconductivity in Heavy Fermion UTe2
• Metamagnetic Transition in Heavy Fermion Superconductor UTe2
• Multiple Superconducting Phases and Unusual Enhancement of the Upper Critical Field in UTe2
• Core-Level Photoelectron Spectroscopy Study of UTe${}_2$
• Expansion of the high field-boosted superconductivity in UTe2 under pressure

Cited by in corpus (1)

• Multiple localized-itinerant dualities in magnetism of 5f electron systems. The case of UPt${}_2$Si${}_2$