Appearance of the universal value e(2)/h of the zero-bias conductance in a Weyl semimetal-superconductor junction

摘要

We study the differential conductance of a time-reversal symmetric Weyl semimetal-superconductor junction with an s-wave superconducting state. We find that there exists an extended regime where the zero-bias differential conductance acquires the universal value of e(2)/h per channel, independent of the pairing and chemical potentials on each side of the junction, due to a perfect cancellation of Andreev and normal reflection contributions. This universal conductance can be attributed to the interplay of the unique spin/orbital-momentum locking and s-wave pairing that couples Weyl nodes of the same chirality. We expect that the universal conductance can serve as a robust and distinct signature for time-reversal symmetric Weyl fermions and be observed in the recently discovered time-reversal symmetric Weyl semimetals.