SKM 2021 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 16: PhD Focus Session: Symposium on Strange Bedfellows - Magnetism Meets Superconductivity" (joint session MA/AKjDPG) (joint session MA/TT)

TT 16.7: Invited Talk

Thursday, September 30, 2021, 12:15–12:45, H5

Resonance from antiferromagnetic spin fluctuations for spin-triplet superconductivity in UTe2 — •Pengcheng Dai — Rice University

Superconductivity has its universal origin in the formation of bound (Cooper) pairs of electrons that can move through the lattice without resistance below the superconducting transition temperature Tc. While electron Cooper pairs in most superconductors form anti-parallel spin-singlets with total spin S = 0, they can also form parallel spin-triplet Cooper pairs with S = 1 and an odd parity wavefunction. Spin-triplet pairing is important because it can host topological states and Majorana fermions relevant for fault tolerant quantum computation. However, spin-triplet pairing is rare and has not been unambiguously identified in any solid state systems. Since spin-triplet pairing is usually mediated by ferromagnetic (FM) spin fluctuations, uranium based heavy-fermion UTe2, which has a Tc * 1.6 K, has been identified as a strong candidate for chiral spin-triplet topological superconductor near a FM instability. Here we use inelastic neutron scattering (INS) to show that superconductivity in UTe2 is coupled with a sharp magnetic excitation at the Brillouin zone (BZ) boundary near AF order, analogous to the resonance seen in other exotic superconductors. We find that the resonance in UTe2 occurs below Tc at an energy Er = 7.9kBTc. Since the resonance has only been found in spin-singlet superconductors near an AF instability, its discovery in UTe2 suggests that AF spin fluctuations can also induce spin-triplet pairing for superconductivity.