Anisotropic field-induced changes in the superconducting order parameter of UTe2
arXiv:2310.04938 · doi:10.1103/PhysRevResearch.7.L022053
Abstract
UTe2 is a newly discovered unconventional superconductor, where electron Cooper pairs combine into a spin-triplet ground state. Here we report the specific heat C(H,T) of a high-quality single crystal of UTe2 with a single specific heat anomaly at the superconducting transition temperature T_c {\approx} 2 K and a small zero-field residual Sommerfeld coefficient γ_0 = C/T (T=0) = 10 mJ/mol-K^2. We applied magnetic field up to 12 T along the three principal crystallographic axes of UTe2 to probe the nature of the superconducting state. The evolution of the residual Sommerfeld coefficient as a function of magnetic field, γ_0 (H), is highly anisotropic and reveals distinct regions. In magnetic field up to 4 T applied along a, b, and c axes, we find γ_0{\approx}α_i {\square}H, with i=a,b,c, as expected for an unconventional superconductor with nodes (zeros) of the superconducting order parameter on the Fermi surface. A pronounced kink in γ_0(H), however, is observed at roughly 4 T for field applied along both a and b axes, whereas a smooth change from square-root to linear behaviour is observed at 4 T for H//c. These results strongly indicate that a zero-field ground state is stable up to 4 T and undergoes a field-induced evolution above 4 T. {α_c} > {α_a} > {α_b}, indicating that the nodes in the low-field state are predominantly located in the vicinity of the a-b plane. The modification of the order parameter is strongest when field is applied in the a-b plane, which causes nodes to move away from the direction of the applied field. Both d_(B_2u)+id_(B_1u) and d_(B_2u)+id_(A_u) two-component order parameters can account for our observations, with d_(B_2u)+id_(B_1u) a more likely candidate. In either scenario, our measurements indicate that B_2u is the primary superconducting order parameter in UTe2.
References in corpus (19)
- Topological properties of spin-triplet superconductors and the Fermi surface topology in the normal state
- Metamagnetic Transition in Heavy Fermion Superconductor UTe2
- Unusual upper critical field of the ferromagnetic superconductor UCoGe
- Topological Blount's theorem of odd-parity superconductors
- Low energy band structure and symmetries of UTe2 from angle resolved photoemission spectroscopy
- Low-dimensional antiferromagnetic fluctuations in the heavy-fermion paramagnetic ladder UTe
- Large Reduction in the -axis Knight Shift on UTe with = 2.1 K
- Superconducting order parameter in UTe determined by Knight shift measurement
- Orientational field-dependence of low-lying excitations in mixed state of unconventional superconductors
- Magnetic-Field-Induced Phenomena in the Paramagnetic Superconductor UTe
- Anisotropic response of spin susceptibility in the superconducting state of UTe probed with Te-NMR measurement
- Unconventional superconductors under rotating magnetic field I: density of states and specific heat
- Single-Component Superconductivity in UTe at Ambient Pressure
- A review of UTe at high magnetic fields
- The fate of time-reversal symmetry breaking in UTe2
- Absence of Spontaneous Magnetic Fields Due to Time-Reversal Symmetry Breaking in Bulk Superconducting UTe2
- Inhomogeneous Superconducting State Probed by Te NMR on UTe$_2
- Superconductivity in disordered locally noncentrosymmetric materials: an application to CeRhAs
- Theory of the low- and high-field superconducting phases of UTe