Possible breaking of the Pauli limit in Sn_1-xIn_xTe/III-V heterostructures

Sn_1-xIn_xTe has been synthesized and studied as a candidate topological superconductor. In recent years, scientists start to explore its thin film form. Up to now, the superconducting behavior in Sn_1-xIn_xTe seems to follow traditional BCS theory.

Here we report transport studies of Sn_1-xIn_xTe/(Ga,In)(As,Sb), grown by molecular beam epitaxy. Band bending between two layers causes a depletion region at the interface. By varying the composition of (Ga,In)(As,Sb), we are able to tune the strength of band bending and modify the superconducting properties of Sn_1-xIn_xTe. Interestingly, we have observed a breaking of the Pauli limit in Sn_0.7In_0.3Te/Ga_0.52In_0.48Sb heterostructure. Meanwhile, Pauli limit is preserved in Sn_0.7In_0.3Te layers grown on wide-gap BaF₂ substrate, where no band bending occurs. The result indicates the existence of unconventional superconductivity emerging on Sn_1-xIn_xTe in the 2D limit. Our work has also shown a possible way of engineering the superconducting properties by band bending.