arXiv subjects

Jaechul Lee

Publications and source records attributed to Jaechul Lee.

4 recordsLinked to original sources

arXiv2025

Anomalous proximity effect of a spin-singlet superconductor with a spin-orbit interaction

The anomalous proximity effect of a spin-triplet $p$-wave superconductor has been known as a part of the Majorana physics and is explained by the penetration of zero-energy states from a surface of a superconductor to a dirty normal metal. We demonstrate that a spin-singlet $d$-wave superconductor without any surface zero-energy states exhibits the anomalous proximity effect in the presence of a specific spin-orbit interaction. The results show the quantization of the zero-bias conductance in a dirty normal-metal/superconductor junction. We also discuss a relation between our findings and results in an experiment on a CoSi$_2$/TiSi$_2$ junction.

cond-mat.supr-con↗

arXiv2021

Strong anomalous proximity effect from spin-singlet superconductors

The proximity effect from a spin-triplet $p_x$-wave superconductor to a dirty normal-metal has been shown to result in various unusual electromagnetic properties, reflecting a cooperative relation between topologically protected zero-energy quasiparticles and odd-frequency Cooper pairs. However, because of a lack of candidate materials for spin-triplet $p_x$-wave superconductors, observing this effect has been difficult. In this paper, we demonstrate that the anomalous proximity effect, which is essentially equivalent to that of a spin-triplet $p_x$-wave superconductor, can occur in a semiconductor/high-$T_c$ cuprate superconductor hybrid device in which two potentials coexist: a spin-singlet $d$-wave pair potential and a spin--orbit coupling potential sustaining the persistent spin-helix state. As a result, we propose an alternative and promising route to observe the anomalous proximity effect related to the profound nature of topologically protected quasiparticles and odd-frequency Cooper pairs.

cond-mat.supr-con↗

arXiv2020

Odd-parity pairing correlations in a d-wave superconductor

We theoretically study the effects of spin-orbit interactions on symmetry of a Cooper pair in a spin-singlet d-wave superconductor in two-dimension. The pairing symmetry is analyzed in terms of the anomalous Green's function which is obtained by solving the Gor'kov equation analytically. A spin-orbit interaction induces a spin-triplet p-wave pairing correlation in a uniform superconductor. An odd-frequency spin-triplet s-wave pairing correlation appears at a surface of such superconductor as a result of breaking inversion symmetry locally. We also discuss a close relationship among the odd-frequency pairing correlation, chirality of surface bound states at the zero energy, and the anomalous proximity effect. The obtained results enable us to design a superconductor which causes the strong anomalous proximity effect.

cond-mat.supr-con↗

arXiv2019

Proximity effect in a ferromagnetic semiconductor with spin-orbit interactions

We study theoretically the proximity effect in a ferromagnetic semiconductor with Rashba spin-orbit interaction. The exchange potential generates opposite-spin-triplet Cooper pairs which are transformed into equal-spin-triplet pairs by the spin-orbit interaction. In the limit of strong spin-orbit interaction, symmetry of the dominant Cooper pair depends on the degree of disorder in a ferromagnet. In the clean limit, spin-singlet $s$-wave Cooper pairs are the most dominant because the spin-momentum locking stabilizes a Cooper pair consisting of a time-reversal partner. In the dirty limit, on the other hand, equal-spin-triplet $s$-wave pairs are dominant because random impurity potentials release the locking. We also discuss the effects of the spin-orbit interaction on the Josephson current.

cond-mat.supr-con↗