arXiv subjects

Marie Ohuchi

Publications and source records attributed to Marie Ohuchi.

4 recordsLinked to original sources

arXiv2020

Charging in the vortex lattice of type-II superconductors

We study the magnetic-field dependence of the vortex-core charge in the Abrikosov lattice of an $s$-wave superconductor based on the augmented quasiclassical equations, where we incorporate the pair-potential gradient (PPG) terms characteristic of charging in superconductors besides the well-known Lorentz force. Our numerical results at $T=0.2 T_{\rm c}$ and $0.5 T_{\rm c}$ reveal that periodic charge redistribution is superimposed on the magnetic flux-line lattice with different spatial patterns at different fields. The PPG terms are dominant at weak fields over the Lorentz force for accumulating charge in the vortex cores, whereas the Lorentz force prevails at higher fields to give rise to a peak structure in the core charge around $H\sim \frac{1}{2}H_{{\rm c}2}$. We estimate the peak value of the core charge at $T=0.2 T_{\rm c}$ using parameters appropriate for cuprates to obtain a large value of $Q \sim 10^{-2} |e|$ in the core region of radius $0.2 \xi_0$ in the $ab$ plane and length $1 \ {\rm nm}$ along the $c$ axis.

cond-mat.supr-con↗

arXiv2019

Drastic enhancement of the thermal Hall angle in a $d$-wave superconductor

A drastic enhancement of the thermal Hall angle in $d$-wave superconductors was observed experimentally in a cuprate superconductor and in CeCoIn$_5$ at low temperatures and very weak magnetic field [Phys. Rev. Lett. $\bf 86$, 890 (2001); Phys. Rev. B $\bf 72$, 214515 (2005)]. However, to the best of our knowledge, its microscopic calculation has not been performed yet. To study this microscopically, we derive the thermal Hall coefficient in extreme type-II superconductors with an isolated pinned vortex based on the augmented quasiclassical equations of superconductivity with the Lorentz force. Using it, we can confirm that the quasiparticle relaxation time and the thermal Hall angle are enhanced in $d$-wave superconductors without impurities of the resonant scattering because quasiparticles around the gap nodes which become dominant near zero temperature are restricted to the momentum in a specific orientation. This enhancement of the thermal Hall angle may also be observed in other nodal superconductors with large magnetic-penetration depth.

cond-mat.supr-con↗

arXiv2018

Charging in a Superconducting Vortex Due to the Three Force Terms in Augmented Eilenberger Equations

We derive augmented Eilenberger equations that incorporate the following missing force terms: (i) the Lorentz force, (ii) the pair-potential gradient (PPG) force, and (iii) the pressure difference arising from the slope in the density of states (DOS). Recently, augmented Eilenberger equations with the Lorentz and PPG forces have been derived microscopically by studying the Hall and charging effects in superconductors, but the pressure due to the slope in the DOS has not yet been considered in augmented Eilenberger equations, despite phenomenological indications that it is a charging mechanism in a vortex of type-II superconductors. This newly added pressure is called "the SDOS pressure". We calculate the charging in an isolated vortex of an s-wave superconductor with a spherical Fermi surface using the augmented Eilenberger equations incorporating the Lorentz force, PPG force, and SDOS pressure. When we compare the charge densities due to the three force terms in the augmented Eilenberger equations, the vortex-core charging due to the SDOS pressure is larger than that due to the other forces near the superconducting transition temperature. Thus, when we calculate the charging in an isolated vortex of a superconductor with a finite slope in the DOS, we should consider not only the Lorentz and PPG forces but also the SDOS pressure.

cond-mat.supr-con↗

arXiv2017

Charging due to Pair-Potential Gradient in Vortex of Type-II Superconductors

Besides the magnetic Lorentz force familiar from the Hall effect in metals and semiconductors, there exists a mechanism for charging peculiar to superconductors that is caused by the pair-potential gradient (PPG). We incorporate it in the augmented quasiclassical equations of superconductivity with the Lorentz force to study charging of an isolated vortex in an equilibrium s-wave type-II superconductor. It is found that the PPG mechanism gives rise to charging concentrated within the core whose magnitude at the core center can be 10 to 100 times larger than that caused by the Lorentz force. Our detailed calculations on the spatial, temperature, and magnetic-penetration-depth dependences of the vortex-core charge reveal that the PPG mechanism contributes dominantly to the core charging of the isolated vortex over a wide parameter range. The two mechanisms are also found to work additively at the core center for the present model with an isotropic Fermi surface.

cond-mat.supr-con↗