Evidence of a two-component order parameter in 4Hb-TaS2 in the Little-Parks effect

Abstract

Finding unambiguous evidence of non-trivial pairing states is one of the greatest experimental challenges in the field of unconventional superconductivity. Such evidence requires phase-sensitive probes susceptible to the internal structure of the order parameter. We measure the Little-Parks effect to provide clear evidence of an unconventional superconducting order parameter in 4Hb-TaS${}_2$. Namely, we find a $\pi$-shift in the transition-temperature oscillations of rings made of a single crystal. We argue that such an effect can only occur if the underlying order parameter belongs to a two-dimensional representation, in other words there are two degenerate order parameters right at the transition. Additionally, we show that $T_c$ is enhanced as a function of the out-of-plane field when a constant in-plane field is applied. Such an increase is consistent with a chiral state, which again, in general only emerges from a two-component order parameter. In combination with previous experiments, our results strongly indicate that 4Hb-TaS${}_2$ indeed realizes a chiral superconductor.

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Cited by in corpus (13)

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• Darkness in interlayer and charge density wave states of 2H-TaS2
• Probing enhanced superconductivity in van der Waals polytypes of V${}_x$TaS${}_2$
• Nodeless superconductivity in 4H${}_b$-TaS${}_2$ with broken time reversal symmetry
• Reciprocal and nonreciprocal paraconductivity in bilayer multiphase superconductors
• Self-consistent evaluation of proximity and inverse proximity effects with pair-breaking in diffusive SN junctions
• Charge Density Waves in the 2.5-Dimensional Quantum Heterostructure
• Anomalous currents and spontaneous vortices in spin-orbit coupled superconductors
• Topological pair density waves in kagome superconductors
• Signature of chiral superconducting order parameter evidenced in mesoscopic superconductors
• Pair-mixing induced Time-reversal-breaking superconductivity
• Strain-induced Berry phase in chiral superconductors
• Observation of field-odd and field-free superconducting diode effects in ${\mathrm{Mo}}_2\mathrm{C}$ nanoflakes