Beyond triplet: Unconventional superconductivity in a spin-3/2 topological semimetal
- Univ. of Maryland, College Park, MD (United States); Ames Lab., Ames, IA (United States)
- Univ. of Maryland, College Park, MD (United States)
- Univ. of Maryland, College Park, MD (United States); Univ. of Central Florida, Orlando, FL (United States)
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS)
- Univ. of Maryland, College Park, MD (United States); Univ. of Otago, Dunedin (New Zealand)
- Univ. of Wisconsin, Madison, WI (United States)
- Ames Lab., Ames, IA (United States)
In all known fermionic super fluids, Cooper pairs are composed of spin-1/2 quasi-particles that pair to form either spin-singlet or spin-triplet bound states. The "spin" of a Bloch electron, however, is xed by the symmetries of the crystal and the atomic orbitals from which it is derived, and in some cases can behave as if it were a spin-3/2 particle. The superconducting state of such a system allows pairing beyond spin-triplet, with higher spin quasi-particles combining to form quintet or even septet pairs. Here, we report evidence of unconventional superconductivity emerging from a spin-3/2 quasiparticle electronic structure in the half-Heusler semimetal YPtBi, a low-carrier density noncentrosymmetric cubic material with a high symmetry that preserves the p-like j = 3/2 manifold in the Bi-based Γ8 band in the presence of strong spin-orbit coupling. With a striking linear temperature dependence of the London penetration depth, the existence of line nodes in the superconducting order parameter Δ is directly explained by a mixed-parity Cooper pairing model with high total angular momentum, consistent with a high-spin fermionic super fluid state. We propose a k ∙ p model of the j = 3/2 fermions to explain how a dominant J=3 septet pairing state is the simplest solution that naturally produces nodes in the mixed even-odd parity gap. Together with the underlying topologically non-trivial band structure, the unconventional pairing in this system represents a truly novel form of super fluidity that has strong potential for leading the development of a new generation of topological superconductors.
- Research Organization:
- Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Ames Laboratory (AMES), Ames, IA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- Grant/Contract Number:
- AC02-05CH11231; DMREF-1335215; SC-0010605; AC02-07CH11358; GBMF4419
- OSTI ID:
- 1460308
- Alternate ID(s):
- OSTI ID: 1433652
- Report Number(s):
- IS-J 9234; ark:/13030/qt6r34j85g
- Journal Information:
- Science Advances, Vol. 4, Issue 4; ISSN 2375-2548
- Publisher:
- AAASCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
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