Enhanced spin-triplet superconductivity near dislocations in Sr2RuO4

Abstract

Superconductors with a chiral p-wave pairing are of great interest because they could support Majorana modes that could enable the development of topological quantum computing technologies that are robust against decoherence. Sr 2 RuO 4 is widely believed to be a chiral p-wave superconductor. Yet, the mechanism by which superconductivity emerges in this, and indeed most other unconventional superconductors, remains unclear. Here we show that the local superconducting transition temperature in the vicinity of lattice dislocations in Sr 2 RuO 4 can be up to twice that of its bulk. This is all the more surprising for the fact that disorder is known to easily quench superconductivity in this material. With the help of a phenomenological theory that takes into account the crystalline symmetry near a dislocation and the pairing symmetry of Sr 2 RuO 4 , we predict that a similar enhancement should emerge as a consequence of symmetry reduction in any superconductor with a two-component order parameter.

Little-Parks oscillations with half-quantum fluxoid features in Sr2RuO4 microrings

“…It should also be mentioned that a superconducting state can exist with an enhanced transition temperature, the so-called 3-K phase. This is observed in eutectic crystals [28][29][30] or in bulk crystals under uniaxial strain [31][32][33].…”

“…It should also be mentioned that a superconducting state can exist with an enhanced transition temperature, the so-called 3-K phase. This is observed in eutectic crystals [28][29][30] or in bulk crystals under uniaxial strain [31][32][33].Fluxoid quantization can be investigated by measuring magnetoresistance oscillations as a function of a field applied along the axis of the ring in the regime of the resistive transition, known as the Little-Parks (LP) oscillations [34]. The LP oscillations originate from the oscillations in the free energy and hence in the transition temperature T c , caused by field-induced supercurrents that flow to satisfy the quantization condition.…”

Enhanced superconductivity at the interface ofW/Sr2RuO4point contacts

“…This enhanced T c is consistent with previous susceptibility measurements on bulk SRO sample under uniaxial pressure, where the mechanism of T c enhancement was ascribed to anisotropic lattice distortion, 21,22,25 similar to that found in the eutectic 3K phase. 26,27 In Figs. 2 and 3, for easy comparison with theoretical description, dV /dI is converted to dI/dV .…”

Higher-Tc Superconducting Phase in Sr2RuO4 Induced by In-Plane Uniaxial Pressure

“…Previous studies on the Sr 2 RuO 4 -Ru eutectic, Sr 2 RuO 4 under out-of-plane UAP, and Sr 2 RuO 4 around dislocations all indicate that Sr 2 RuO 4 has a maximal T c of about 3 K. 27,36,37 In this study, we have newly clarified that the higher-T c SC phase is also induced in pure Sr 2 RuO 4 by in-plane UAP. As a common feature of these higher-T c SC phases, the lattice is distorted and the in-plane crystal symmetry is expected to be reduced at least in part of the sample.…”

“…2 and 5. In the cases of both P [100] and P [110] , the onset T c decreases to about 2.5 K, and the shielding fraction is markedly suppressed in the temperature range between the original bulk T c at ambient pressure and 3.3 K. These results indicate that the higher-T c superconductivity under in-plane UAP is induced mainly by elastic distortion, although plastic distortion, such as dislocation, 36 should also play some role because the onset T c after pressure release is still higher than the original value. Figure 5 shows the temperature dependence of the imagi- ∆χ'' (normalized) nary part of the AC susceptibility of Sr 2 RuO 4 under in-plane UAP.…”