Chiral superconductivity in UTe2 probed by anisotropic low-energy excitations

Abstract

Chiral spin-triplet superconductivity is a topologically nontrivial pairing state with broken time-reversal symmetry, which can host Majorana quasiparticles. The recently discovered heavy-fermion superconductor UTe${}_2$ exhibits peculiar properties of spin-triplet pairing, and the possible chiral state has been actively discussed. However, the symmetry and nodal structure of its order parameter in the bulk, which determine the Majorana surface states, remains controversial. Here we focus on the number and positions of superconducting gap nodes in the ground state of UTe${}_2$. Our magnetic penetration depth measurements for three field orientations in the Meissner state reveal the power-law temperature dependence with exponents nearly equal to 2 or less than 2, which excludes single-component spin-triplet states. The anisotropy of low-energy quasiparticle excitations indicates multiple point nodes near the $k_y$- and $k_z$-axes, evidencing that the order parameter has multiple components in a chiral complex form. We find that most consistent is a chiral $B_{3u}+i{A}_u$ non-unitary state, which provides fundamentals of the topological properties in UTe${}_2$.

40 pages, 17 figures

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Cited by in corpus (41)

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• Single-Component Superconductivity in UTe${}_2$ at Ambient Pressure
• A review of UTe${}_2$ at high magnetic fields
• The fate of time-reversal symmetry breaking in UTe2
• Fully gapped pairing state in spin-triplet superconductor UTe${}_2$
• Absence of Spontaneous Magnetic Fields Due to Time-Reversal Symmetry Breaking in Bulk Superconducting UTe2
• Longitudinal spin fluctuations driving field-reinforced superconductivity in UTe${}_2$
• Molten Salt Flux Liquid Transport Method for Ultra Clean Single Crystals UTe2
• Pairing symmetries of multiple superconducting phases in UTe2: Competition between ferromagnetic and antiferromagnetic fluctuations
• Pair Wavefunction Symmetry in UTe2 from Zero-Energy Surface State Visualization
• Thermodynamic transitions and topology of spin-triplet superconductivity: Application to UTe${}_2$
• Theory of the low- and high-field superconducting phases of UTe${}_2$
• Anisotropic field-induced changes in the superconducting order parameter of UTe2
• Anisotropic paramagnetic response of topological Majorana surface states in the superconductor ${\text{UTe}}_2$
• Unconventional $s$-Wave Pairing with Point-Node-Like Gap Structure in UTe${}_2$
• Spectroscopic evidence of symmetry breaking in the superconducting vortices of UTe2
• Nodal superconducting gap structure and topological surface states of UTe${}_2$
• Theoretical studies on off-axis phase diagrams and Knight shifts in UTe${}_2$ -- Tetra-critical point, d-vector rotation, and multiple phases
• Spin caloritronics as a probe of nonunitary superconductors
• Majorana multipole response with magnetic point group symmetry
• Lifting of gap nodes by disorder in ultranodal superconductor candidate FeSe1-xSx
• Self-reconstruction of order parameter in spin-triplet superconductor UTe${}_2$
• Quasiparticle interference and spectral function of the UTe${}_2$ superconductive surface band
• Thermal conductivity of nonunitary triplet superconductors: application to UTe${}_2$
• Microscopic theory of pair density waves in spin-orbit coupled Kondo lattice
• Determination of the magnetic penetration depth with measurements of the vortex-penetration field for type-II superconductors
• Higher-order topological phases for time-reversal-symmetry breaking superconductivity in UTe${}_2$
• Topological superconductivity in a spin-orbit coupled Kondo lattice
• Magnetic edge fields in UTe${}_2$ near zero background fields
• $b$-axis and $c$-axis Knight shift measurements in the superconducting state on ultraclean UTe${}_2$ with $T_c$ = 2.1 K
• Nodal Superconductivity of UTe${}_2$ Probed by Field-Angle-Resolved Specific Heat on a Crystal with $T_{\mathrm{c}}=2.1$ K
• Visualizing the Odd-parity Superconducting Order Parameter and its Quasiparticle Surface Band in UTe2
• Revealing isotropic abundant low-energy excitations in UTe${}_2$ through complex microwave surface impedance
• Spin-lattice relaxation for point-node-like s-wave superconductivity in f-electron systems
• Quasiparticle Interference of Spin-Triplet Superconductors: Application to UTe${}_2$
• Theoretical Study of Impurity Effects on Superconductivity in UTe2
• Pair-mixing induced Time-reversal-breaking superconductivity
• Electronic structure of UTe${}_2$ under pressure
• Determination of the London penetration depth with the tunnel diode oscillator technique
• Resolving the Thermal Paradox: Many-body localization or fractionalization?
• Exotic Topological Phenomena in Chiral Superconducting States on Doped Quantum Spin Hall Insulators with Honeycomb Lattices