arXiv subjects

Shunichiro Kittaka

Publications and source records attributed to Shunichiro Kittaka.

40 records · Page 3Linked to original sources

arXiv2011

Evaluation of Spin-Triplet Superconductivity in Sr2RuO4

This review presents a summary and evaluations of the superconducting properties of the layered ruthenate Sr2RuO4 as they are known in the autumn of 2011. This paper appends the main progress that has been made since the preceding review by Mackenzie and Maeno was published in 2003. Here, special focus is placed on the critical evaluation of the spin-triplet, odd-parity pairing scenario applied to Sr2RuO4. After an introduction to superconductors with possible odd-parity pairing, accumulated evidence for the pairing symmetry of Sr2RuO4 is examined. Then, significant recent progress on the theoretical approaches to the superconducting pairing by Coulomb repulsion is reviewed. A section is devoted to some experimental properties of Sr2RuO4 that seem to defy simple explanations in terms of currently available spin-triplet scenario. The next section deals with some new developments using eutectic boundaries and micro-crystals, which reveals novel superconducting phenomena related to chiral edge states, odd-frequency pairing states, and half-fluxoid states. Some of these properties are intimately connected with the properties as a topological superconductor. The article concludes with a summary of knowledge emerged from the study of Sr2RuO4 that are now more widely applied to understand the physics of other unconventional superconductors, as well as with a brief discussion of relatively unexplored but promising areas of ongoing and future studies of Sr2RuO4.

cond-mat.supr-con↗

arXiv2010

Higher-Tc superconducting phase in Sr2RuO4 induced by uniaxial pressure

We have investigated uniaxial pressure effect on superconductivity of pure Sr2RuO4, whose intrinsic superconducting transition temperature Tc is 1.5 K. It was revealed that a very low uniaxial pressure along the c axis, only 0.2 GPa, induces superconductivity with the onset Tc above 3 K. The present results indicate that pure Sr2RuO4 has two superconducting phases with Tc = 1.5 K and with varying Tc up to 3.2 K. The latter phase exhibits unusual features and is attributable to anisotropic crystal distortions beyond the elastic limit.

cond-mat.supr-con↗

arXiv2009

Large Enhancement of 3-K Phase Superconductivity in the Sr2RuO4-Ru Eutectic System by Uniaxial Pressure

While the superconducting transition temperature Tc of Sr2RuO4 is 1.5 K, its onset Tc is enhanced as high as 3 K in the Sr2RuO4-Ru eutectic system, which is often referred to as the 3-K phase. We have investigated effects of uniaxial pressure on the non-bulk superconductivity in the 3-K phase. While Tc of pure Sr2RuO4 is known to be suppressed by hydrostatic pressure, a large enhancement of the superconducting volume fraction of the 3-K phase was observed for both out-of-plane and in-plane uniaxial pressures. Especially, under the in-plane pressure, the shielding fraction at 1.8 K of only less than 0.5% at 0 GPa exceeds 40% at 0.4 GPa. Such a large shielding fraction suggests that under the uniaxial pressure interfacial 3-K phase superconductivity penetrates deep into the bulk of Sr2RuO4. The present finding provides a significant implication to the unresolved origin of the enhancement of Tc to 3 K in the Sr2RuO4-Ru eutectic system.

cond-mat.supr-con↗

arXiv2009

Spatial development of superconductivity in the Sr2RuO4-Ru eutectic system

We have clarified how the enhanced superconductivity, often referred to as the 3-K phase superconductivity, develops in the Sr2RuO4-Ru eutectic system. From the detailed ac and dc susceptibility measurements on well-characterized crystals, we revealed strongly anisotropic shielding, governed by the direction of the screening current dominated within the RuO2 plane rather than by the orientation of the Ru lamellae. The onset temperature of the 3-K phase superconductivity probed by diamagnetic screening is as high as 3.5 K. The temperature dependence of the diamagnetic shielding above around 2 K is well ascribed by the interfacial screening around each Ru lamella. Below around 2 K, the rapid development of the shielding fraction as well as its peculiar esponse to ac and dc magnetic fields are explained by the formation of the Josephson network consisting of inter-lamellar supercurrents.

cond-mat.supr-con↗