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Anisotropic fully gapped superconductivity in quasi-one-dimensional ${Li}_{0.9} {Mo}_{6} O_{17}$

M. J. Grant ¹, T. M. Huijbregts ¹, R. Nicholls ¹, M. Greenblatt ², P. Chudzinski ^3,4, A. Carrington ¹, and N. E. Hussey ^1,5

¹H. H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, United Kingdom
²Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey, USA
³School of Mathematics and Physics, Queen's University Belfast, Belfast, United Kingdom
⁴Institute of Fundamental Technological Research, Polish Academy of Sciences, Warsaw, Poland
⁵High Field Magnet Laboratory (HFML-FELIX) and Institute for Molecules and Materials, Radboud University, Nijmegen, Netherlands

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Phys. Rev. B 113, 094524 – Published 24 March, 2026

DOI: https://doi.org/10.1103/y4fj-8c2m

Abstract

Superconductivity in quasi-one-dimensional ${Li}_{0.9} {Mo}_{6} O_{17}$ emerges from an exotic, nonmetallic normal state that exhibits signatures of Tomonaga-Luttinger liquid behavior, emergent symmetry, and excitonic order. The high upper critical field, $H_{c 2}$ , in ${Li}_{0.9} {Mo}_{6} O_{17}$ suggests that that the favored pairing state is spin-triplet in nature. Here, we report measurements of the magnetic penetration depth down to $0.08 K$ ( $T / T_{c} ≲ 0.04$ ) and the specific heat down to $0.4 K$ ( $T / T_{c} ≲ 0.2$ ), and show that they are consistent with a moderately coupled, fully gapped superconducting state with marked gap anisotropy and a minimum ( $Δ_{\min} ≃ 0.4 k_{B} T_{c}$ ) occurring over a very narrow region in $k$ space. Combined with knowledge of $H_{c 2}$ , these measurements support the presence of a nodeless and possibly odd-parity spin-triplet superconducting order parameter in ${Li}_{0.9} {Mo}_{6} O_{17}$ .

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Phys. Rev. B 113, 094524– Published 24 March, 2026

Vol. 113, Iss. 9 — 1 March 2026

Received 1 May 2025
Revised 18 February 2026
Accepted 24 February 2026

DOI: https://doi.org/10.1103/y4fj-8c2m

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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Anisotropic fully gapped superconductivity in quasi-one-dimensional ${Li}_{0.9} {Mo}_{6} O_{17}$

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Anisotropic fully gapped superconductivity in quasi-one-dimensional Li0.9Mo6O17

Abstract

Physics Subject Headings (PhySH)

Article Text

Supplemental Material

References (52)

Anisotropic fully gapped superconductivity in quasi-one-dimensional ${Li}_{0.9} {Mo}_{6} O_{17}$