Thickness changes the superconducting response of 3R-TaSe₂
Flakes just two unit cells thick remained superconducting in a parallel magnetic field more than three times the Pauli limit.
The team measured a transition temperature of 2.89 K in bulk 3R-TaSe₂ before comparing flakes of different thicknesses. In two-unit-cell flakes, the in-plane upper critical field exceeded three times the Pauli limit, consistent with Ising superconductivity.
Flakes four and eight unit cells thick showed different features under a parallel magnetic field. The authors interpreted these as evidence for an orbital FFLO state, in which superconducting pairing varies across space. Liyuan Zhang, Zhigang Cheng and Jian-gang Guo are corresponding authors of the Advanced Functional Materials paper.