Identifying Bogoliubov Fermi surfaces via thermoelectric response in a d-wave superconductor heterostructure

We theoretically investigate the thermoelectric response of Bogoliubov Fermi surfaces (BFSs) generated in a two-dimensional unconventional d-wave superconductor subjected to an external in-plane Zeeman field. These BFSs exhibiting the same dimension as the underlying normal-state Fermi surface are topologically protected by combinations of discrete symmetries. Utilizing the Blonder-Tinkham-Klapwijk formalism and considering a normal-d-wave superconductor hybrid junction, we compute the thermoelectric coefficients including thermal conductance, Seebeck coefficient, and figure of merit (zT ), and examine the validation of the Widemann-Franz law in the presence of both voltage and temperature bias. Importantly, as a signature of the anisotropic nature of d-wave pairing, Andreev bound states (ABSs) formed at the normal-superconductor interface play a significant role in the thermoelectric response. In the presence of ABSs, we observe a substantial enhancement in the Seebeck coefficient (similar to 200 mu V/ K) and zT (similar to 3.5) due to the generation of the BFSs and thus making such setup a potential candidate for device applications. Finally, we strengthen our continuum model results by computing the thermoelectric coefficients based on a lattice-regularized version of our continuum model.