Thermodynamic and electrical transport properties of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi mathvariant="normal">UTe</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math> under uniaxial stress
C Girod, Callum R. Stevens, Andrew Huxley, E. D. Bauer, F.B. Santos, J. D. Thompson, Rafael M. Fernandes, Jian‐Xin Zhu, F. Ronning, P. F. S. Rosa, S. M. Thomas
Abstract
Despite intense experimental efforts, the nature of the unconventional superconducting order parameter of ${\mathrm{UTe}}_{2}$ remains elusive. This puzzle stems from reports of either a single or a double superconducting transition at ambient pressure as well as a complex pressure-temperature phase diagram. To address this issue, we measured the heat capacity and electrical resistivity of ${\mathrm{UTe}}_{2}$ under compressive uniaxial stress $\ensuremath{\sigma}$ applied along different crystallographic directions. We find that the critical temperature ${T}_{\mathrm{c}}$ of the single observed bulk superconducting transition decreases with $\ensuremath{\sigma}$ along [100] and [110] but increases with $\ensuremath{\sigma}$ along [001]. Aside from its effect on ${T}_{\mathrm{c}}$, $c$-axis stress leads to a significant piezoresistivity. Importantly, an in-plane shear stress ${\ensuremath{\sigma}}_{xy}$ does not induce any observable splitting of the superconducting transition over a stress range of ${\ensuremath{\sigma}}_{xy}\ensuremath{\approx}0.17\phantom{\rule{0.28em}{0ex}}\mathrm{GPa}$. This result suggests that the superconducting order parameter of ${\mathrm{UTe}}_{2}$ may be single component at ambient pressure.