Probing the topological character of superconductors via nonlocal Hanbury Brown and Twiss correlations

Superconductors can be classified as topological or not based on whether time-reversal symmetry, chiral symmetry, and particle-hole symmetry are preserved or not. Further, topological superconductors can also be classified as chiral or helical. In this paper, using Hanbury Brown and Twiss (HBT) shot-noise correlations and the nonlocal conductance, we probe metal and two-dimensional unconventional superconductor and metal junctions to understand better the pairing topological vs nontopological or helical vs chiral or nodal vs gapful. We see that HBT correlations are asymmetric as a function of bias voltage for nontopological superconductors, whereas they are symmetric for topological superconductors irrespective of the barrier strength. Topological superconductors are associated with Majorana fermions which are important for topological quantum computation. By distinguishing topological superconductors from nontopological superconductors, our study will help search for Majorana fermions, which will aid in designing a topological quantum computer.