Large enhancement of superconducting transition temperature in single-element superconducting rhenium by shear strain

Abstract

Finding a physical approach for increasing the superconducting transition temperature (Tc) is a challenge in the field of material science. Shear strain effects on the superconductivity of rhenium were investigated using magnetic measurements, X-ray diffraction, transmission electron microscopy, and first-principles calculations. A large shear strain reduces the grain size and simultaneously expands the unit cells, resulting in an increase in Tc. Here we show that this shear strain approach is a new method for enhancing Tc and differs from that using hydrostatic strain. The enhancement of Tc is explained by an increase in net electron–electron coupling rather than a change in the density of states near the Fermi level. The shear strain effect in rhenium could be a successful example of manipulating Bardeen–Cooper–Schrieffer-type Cooper pairing, in which the unit cell volumes are indeed a key parameter.

Pressure induced superconductivity in MnSe

“…On the other hand, superconducting T c of rhenium under pressure was found to enhance along with increasing lattice strain. Detailed structural analysis of Rh case shows the grain size is reduced accompanying unit cell expansion suggesting that the enhancement in T c is due to the shear stress 44 . The rhenium result is in line with the observed T c increasing in MnSe at the pressure range where the material is orthorhombic.…”

“…The correlation between the superconducting T c with lattice strain of materials has been investigated either in the presence of defects 43 or under pressure 44 . The increase in lattice strain due to the presence of Mg vacancies was found to supress T c of MgB 2 43 .…”

Hydrostatic Compression Effects on Fifth-Group Element Superconductors V, Nb, and Ta Subjected to High-Pressure Torsion

“…It is known to be effective in increasing T c of superconductors such as Nb 10) and Re. 12) There we have to consider both the intergrain network via grain boundary and intragrain crystallinity as factors to influence T c . The strain installed in the SPD process is relatively evaluated via semi-experimental manner: In the case of high-pressure torsion (HPT), 1317) which is one of the SPD techniques along with equal-channel angular pressing 18) and accumulative roll bonding, 19,20) the revolution number N is a parameter to pursue the grain refinement.…”

Critical Temperature in Bulk Ultrafine-Grained Superconductors of Nb, V, and Ta Processed by High-Pressure Torsion

“…In contrast to homogeneous bulk superconductors, bulk nanostructured superconductors generated by SPD provide a new route to control superconducting property, because ultrafine-grain structures with a high density of grain boundaries, dislocations, and other crystalline defects interact with the superconducting order parameter, which varies with the superconducting coherence length (several tens of nanometers). Recently, the HPT process has been applied to Nb, 21) Re, 22) and NbTi, 23) and enhancement of the critical temperature T c , 21,22) upper critical field H c2 21) and critical current density J c 21) has been reported. For mechanisms of the T c -enhancement, the increase of the superconducting order parameter due to the quantum size effect 46,21) and the increase of electronelectron coupling 22) have been discussed in the ultrafine-grained superconductors with a grain size comparable to the coherence length.…”

“…Recently, the HPT process has been applied to Nb, 21) Re, 22) and NbTi, 23) and enhancement of the critical temperature T c , 21,22) upper critical field H c2 21) and critical current density J c 21) has been reported. For mechanisms of the T c -enhancement, the increase of the superconducting order parameter due to the quantum size effect 46,21) and the increase of electronelectron coupling 22) have been discussed in the ultrafine-grained superconductors with a grain size comparable to the coherence length. However, the effect of SPD on the superconducting property is not simple because of competing effects on superconductivity.…”