microstructures

We revisited the temperature-pressure (T−p) phase diagram of CeRhIn₅ utilizing microstructures to probe the electrical resistivity for well-defined crystalline directions along the a- and c-axes of the tetragonal structure. At ambient pressure CeRhIn₅ orders antiferromagnetically below 3.8K. Application of external pressure suppresses the antiferromagnetism and induces an unconventional superconducting (SC) state. The T−p phase diagram obtained on the microstructure resembles that of bulk single crystals. Initially, we observe broad SC transitions in resistivity, which sharpen upon approaching the maximum of the SC dome. The electrical resistivity data in the transition region follows the predictions of the Berezinskii-Kosterlitz-Thouless theory proposed for 2D superconductors, e.g. we find the characteristic non-linear I-V curves for current applied along both a- and c- axes. The latter is not expected for CeRhIn₅ and puts a purely intrinsic origin of the 2D superconductivity related to 2D antiferromagnetic fluctuations in question. That is supported by finite element analysis of strain-fields in the microstructure. Therefore, we speculate that the observed features of 2D superconductivity in CeRhIn₅ may have an origin in a combination of intrinsic and extrinsic effects.