Transport properties of Majorana drumhead surface states in topological nodal-ring superconductors

Abstract

We propose a topological nodal-ring superconductor (TNRSC) by inducing superconductivity on a topological nodal-ring semimetal (NRSM). Such a TNRSC can map to a one-dimensional BDI class topological superconductor and host both ${N}_{\mathrm{BDI}}=1$ and 2 topological phases in the Brillouin zone. These two topological phases support one and two Majorana drumhead surface states, respectively. By virtue of these novel Majorana modes, we find (i) the presence of drumhead surface states can be identified inside the nodal ring, and the radius of the nodal ring can be accurately determined by the zero-bias conductance of a normal-metal (NM)/TNRSC junction; and (ii) the spin-polarized and correlated currents can be generated in the leads of a NM/TNRSC/NM junction. The conclusions are robust even for NRSMs with dispersive drumhead surface states, and they can also apply to the topological NRSM ${\mathrm{HgCr}}_{2}{\mathrm{Se}}_{4}$.