Topological Blount's theorem of odd-parity superconductors

Abstract

From the group theoretical ground, the Blount's theorem prohibits the existence of line nodes for odd-parity superconductors (SCs) in the presence of spin-orbit coupling (SOC). We study the topological stability of line nodes under inversion symmetry. From the topological point of view, we renovate the stability condition of line nodes, in which we not only generalize the original statement, but also establish the relation to zero-energy surface flat dispersions. The topological instability of line nodes in odd-parity SCs implies not the absence of bulk line nodes but the disappearance of the corresponding zero-energy surface flat dispersions due to surface Rashba SOC, which gives an experimental means to distinguish line nodes in odd-parity SCs from those in other SCs.