Nodal Superconductivity of UTe${}_2$ Probed by Field-Angle-Resolved Specific Heat on a Crystal with $T_{\mathrm{c}}=2.1$ K

Abstract

Field-angle-resolved specific-heat measurements were performed on a clean single crystal of a spin-triplet superconductor UTe${}_2$ with $T_{\mathrm{c}}=2.1$ K and a low residual electronic specific heat. At low temperatures, the specific heat exhibits a linear dependence on the magnetic field when the field is applied precisely along the $b$ axis, in stark contrast to its rapid increase at low fields for other orientations. This pronounced anisotropy suggests the presence of nodal quasiparticle excitations with the Fermi velocity predominantly aligned along the $b$ axis. Considering the characteristic field-angle dependences of both the specific heat and the upper critical field, these observations are broadly compatible with theoretical models that assume a superconducting gap structure featuring either point nodes consistent with $B_{2u}$ symmetry, allowed in the infinitely strong spin-orbit coupling scheme, or line nodes confined to flat regions of the quasi-two-dimensional Fermi surface, consistent with ${}^3{B}_{3u}$ symmetry in the finite spin-orbit classification scheme. These results yield crucial hints for resolving the pairing symmetry of UTe${}_2$, paving the way for a deeper understanding of its spin-triplet superconductivity.

6 pages, 4 figures, accepted for publication in J. Phys. Soc. Jpn

References in corpus (26)

• Unconventional Superconductivity in Heavy Fermion UTe2
• Unconventional Superconductivity in UTe2
• Multiple Superconducting Phases and Unusual Enhancement of the Upper Critical Field in UTe2
• Low energy band structure and symmetries of UTe2 from angle resolved photoemission spectroscopy
• First Observation of de Haas-van Alphen Effect and Fermi Surfaces in Unconventional Superconductor UTe2
• Large Reduction in the $a$-axis Knight Shift on UTe${}_2$ with $T_{\mathrm{c}}$ = 2.1 K
• Superconducting order parameter in UTe${}_2$ determined by Knight shift measurement
• Orientational field-dependence of low-lying excitations in mixed state of unconventional superconductors
• Anisotropic response of spin susceptibility in the superconducting state of UTe${}_2$ probed with ${}^{125}$Te-NMR measurement
• Chiral superconductivity in UTe2 probed by anisotropic low-energy excitations
• Quasi-2D Fermi surface in the anomalous superconductor UTe2
• Single-Component Superconductivity in UTe${}_2$ at Ambient Pressure
• The fate of time-reversal symmetry breaking in UTe2
• Fully gapped pairing state in spin-triplet superconductor UTe${}_2$
• Vortex State and Field-Angle Resolved Specific Heat Oscillation for H // ab in d-Wave Superconductors
• Quantum interference between quasi-2D Fermi surface sheets in UTe2
• Superconducting-Spin Reorientation in Spin-Triplet Multiple Superconducting Phases of UTe2
• de Haas-van Alphen Oscillations for the Field Along c-axis in UTe2
• Molten Salt Flux Liquid Transport Method for Ultra Clean Single Crystals UTe2
• Odd-Parity Quasiparticle Interference in the Superconductive Surface State of UTe2
• Searching for zeroes: unconventional superconductors in a magnetic field
• Anomalous Field-Angle Dependence of the Specific Heat of Heavy-Fermion Superconductor UPt3
• Anisotropic field-induced changes in the superconducting order parameter of UTe2
• Theoretical studies on off-axis phase diagrams and Knight shifts in UTe${}_2$ -- Tetra-critical point, d-vector rotation, and multiple phases
• Spectroscopic evidence of symmetry breaking in the superconducting vortices of UTe2
• Observation of Persistent Zero Modes and Superconducting Vortex Doublets in UTe${}_2$