skip to main content


Title: Beyond triplet: Unconventional superconductivity in a spin-3/2 topological semimetal

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 Γ 8 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 ismore » 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.« less
ORCiD logo [1] ;  [2] ;  [3] ;  [2] ; ORCiD logo [2] ; ORCiD logo [2] ;  [2] ; ORCiD logo [2] ; ORCiD logo [4] ;  [5] ;  [6] ; ORCiD logo [7] ; ORCiD logo [7] ; ORCiD logo [2]
  1. Univ. of Maryland, College Park, MD (United States); Ames Lab., Ames, IA (United States)
  2. Univ. of Maryland, College Park, MD (United States)
  3. Univ. of Maryland, College Park, MD (United States); Univ. of Central Florida, Orlando, FL (United States)
  4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS)
  5. Univ. of Maryland, College Park, MD (United States); Univ. of Otago, Dunedin (New Zealand)
  6. Univ. of Wisconsin, Madison, WI (United States)
  7. Ames Lab., Ames, IA (United States)
Publication Date:
Report Number(s):
IS-J 9234
Journal ID: ISSN 2375-2548
Grant/Contract Number:
DMREF-1335215; SC-0010605; AC02-07CH11358; AC02-05CH11231; GBMF4419
Accepted Manuscript
Journal Name:
Science Advances
Additional Journal Information:
Journal Volume: 4; Journal Issue: 4; Journal ID: ISSN 2375-2548
Research Org:
Ames Laboratory (AMES), Ames, IA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1433652