2020/04/30 by Chandan Setty, Yifu Cao, Andreas Kreisel +2
Materials Science · Physics and Astronomy · #Condensed matter physics #Fermi surface #Iron-based superconductors research #Physics #Physics of Superconductivity and Magnetism #Superconductivity #Superfluidity #Topological Materials and Phenomena #cond-mat.mes-hall #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.102.064504
published as Phys. Rev. B 102, 064504 (2020) · 13 pages, 8 figures
openalex created_date 2020/04/10 · arxiv created 2020/08/05 · openalex publication_date 2020/08/05 · arxiv updated 2020/08/12 · openalex updated_date 2026/08/05
Bogoliubov Fermi surfaces (BFSs) are topologically protected regions of zero energy excitations in a superconductor whose dimension equals that of the underlying normal state Fermi surface. Examples of Hamiltonians exhibiting this ``ultranodal'' phase are known to preserve charge-conjugation (C) and parity (P) but break time-reversal (T). In this work, we provide examples of model Hamiltonians that do not necessarily preserve this symmetry pattern but have well-defined sign-changing Pfaffians yielding BFSs. While their topological character has not been recognized previously, some of the models we present have been extensively studied in prior literature. We further examine thermodynamic and electronic properties arising from the ultranodal state. In particular, we study the effect of a weak Zeeman field close to the topological transition and propose distinguishing features of BFSs using residual specific heat and tunneling conductance. Our calculation of the superfluid density in a toy multiband model indicates a window of interband pairing strength where BFSs are stable with a positive superfluid density. We also present additional signatures of BFSs in spin-polarized spectral weight and total magnetization measurements.