High-magnetic-field phases in U_1-xTh_xTe₂

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• The heavy fermion superconductor UTe2 exhibits a complex superconducting phase diagram at low temperatures.
• This phase diagram is sensitive to magnetic field orientation and strength, featuring distinct superconducting phases (SC1, SC2, SCFP) and a field-polarized (FP) phase.

Purpose of the Study:

• To investigate the impact of Thorium (Th) substitution on the magnetic field-dependent superconducting phase diagram of UTe2.
• To understand how increasing disorder affects the different superconducting phases in the U(1-x)ThxTe2 system.

Main Methods:

• Experimental study of the H vs. θ phase diagram for U(1-x)ThxTe2 single crystals at ~0.6 K.
• Systematic variation of Thorium concentration (x) from 0.005 to 0.047.
• Analysis of superconducting phase boundaries and the influence of disorder, indicated by the residual resistance ratio (RRR).

Main Results:

• SC1 phase persists at higher Th concentrations (x=0.047) but with reduced critical field, while SC2 is suppressed.
• SCFP and FP phases remain largely unaffected up to x=0.02.
• SCFP and FP phases are completely suppressed at higher Th concentrations (x=0.025-0.047), correlating with increased disorder (RRR ~3).

Conclusions:

• Thorium substitution tunes the superconducting phase diagram of UTe2, suppressing specific phases like SC2.
• The study highlights the distinct behavior of different superconducting phases under disorder, with SCFP and FP phases showing resilience to moderate disorder but eventual suppression.