Observation of a Pronounced Hebel-Slichter Peak in the Spin-Lattice Relaxation Rate and Implications for Gap and Pairing Symmetry in LaNiGa2

P. Sherpa; R. Hingorani; A. Menon; I. Vinograd; C. Chaffey; A. P. Dioguardi; R. Yamamoto; M. Hirata; F. Ronning; J. R. Badger; P. Klavins; R. R. P. Singh; V. Taufour; N. J. Curro

doi:10.1103/tsnb-1mxc

Observation of a Pronounced Hebel-Slichter Peak in the Spin-Lattice Relaxation Rate and Implications for Gap and Pairing Symmetry in LaNiGa2

P. Sherpa, R. Hingorani, A. Menon, I. Vinograd, C. Chaffey, A. P. Dioguardi, R. Yamamoto, M. Hirata, F. Ronning, J. R. Badger, P. Klavins, R. R. P. Singh, V. Taufour, N. J. Curro

DOI 10.1103/tsnb-1mxc · Physical Review Letters

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Abstract

We report a pronounced Hebel-Slichter coherence peak in the zero field nuclear quadrupolar resonance (NQR) spin-lattice relaxation rate of the topological crystalline superconductor LaNiGa2 in the superconducting state. Previously, a two-band internally antisymmetric nonunitary triplet pairing state was proposed for this system, with equal spin pairing and two distinct gaps associated with different spins. A detailed examination of the temperature dependence of the NQR data shows that the data best fit an internally antisymmetric triplet pairing model if the two gaps are equal and the model is unitary. Even a tiny nonunitarity with two unequal gaps causes the coherence peak to diminish rapidly and deviate from the data. On the other hand, the data are well fit by a two-band singlet Bardeen-Cooper-Schrieffer (BCS)-like pairing with two distinct gaps consistent with previous measurements. This raises doubts on the identification of nonunitary triplet pairing with time-reversal symmetry breaking in this material.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
LaNiGa2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	2.1	Pressure not reported	unknown
LaNiGa2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	1.83	Pressure not reported	unknown