arXiv subjects

D. A. Mayoh

Publications and source records attributed to D. A. Mayoh.

21 records · Page 2Linked to original sources

arXiv2019

Superconductivity and the upper critical field in the chiral noncentrosymmetric superconductor NbRh$_{2}$B$_{2}$

NbRh$_{2}$B$_{2}$ crystallises in a chiral noncentrosymmetric structure and exhibits bulk type-II superconductivity below $7.46(5)$~K. Here we show that the temperature dependence of the upper critical field deviates from the behaviour expected for both Werthamer-Helfand-Hohenberg and the Ginzburg-Landau models and that $μ_{0}H_{\mathrm{c2}}\left(0\right)\approx 18$~T exceeds the Pauli paramagnetic limit, $μ_{0}H_{\mathrm{P}}=13.9$~T. We explore the reasons for this enhancement. Transverse-field muon spectroscopy measurements suggest that the superconducting gap is either $s$-wave or $\left(s+s\right)$-wave, and the pressure dependence of $T_{\mathrm{c}}$ reveals the superconducting gap is primarily $s$-wave in character. The magnetic penetration depth $λ(0) = 595(5)$~nm. Heat capacity measurements reveal the presence of a multigap $\left(s+s\right)$-wave superconducting order parameter and moderate electron-phonon coupling.

cond-mat.supr-con↗

arXiv2018

Multigap Superconductivity in Chiral Noncentrosymmetric TaRh$_{2}$B$_{2}$

We report the first observation of multigap superconductivity in TaRh$_{2}$B$_{2}$. We show TaRh$_{2}$B$_{2}$ is a bulk type-II superconductor with a transition temperature, $T_{\mathrm{c}} = 6.00(5)$ K. We present transverse-field muon spin relaxation data where the superconducting gap can be fit using a two-gap $\left(s+s\right)$-wave model. We also report the zero-field electronic specific heat in the superconducting state that is best described by the same $\left(s+s\right)$ model providing further evidence of multiband behavior in this superconductor. Zero-field muon spin relaxation measurements show time-reversal symmetry is preserved in the superconducting state. We demonstrate that TaRh$_{2}$B$_{2}$ has an upper critical field of $15.2(1)$ T, which is significantly higher than previously reported and exceeds the Pauli limit.

cond-mat.supr-con↗

arXiv2017

Superconducting and normal-state properties of the noncentrosymmetric superconductor Re6Zr

We systematically investigate the normal and superconducting properties of non-centrosymmetric Re$_{6}$Zr using magnetization, heat capacity, and electrical resistivity measurements. Resistivity measurements indicate Re$_{6}$Zr has poor metallic behavior and is dominated by disorder. Re$_6$Zr undergoes a superconducting transition at $T_{\mathrm{c}} = \left(6.75\pm0.05\right)$ K. Magnetization measurements give a lower critical field, $μ_{0}H_{\mathrm{c1}} = \left(10.3 \pm 0.1\right)$ mT. The Werthamer-Helfand-Hohenberg model is used to approximate the upper critical field $μ_{0}H_{\mathrm{c2}} = \left(11.2 \pm 0.2\right)$ T which is close to the Pauli limiting field of 12.35 T and which could indicate singlet-triplet mixing. However, low-temperature specific-heat data suggest that Re$_{6}$Zr is an isotropic, fully gapped s-wave superconductor with enhanced electron-phonon coupling. Unusual flux pinning resulting in a peak effect is observed in the magnetization data, indicating an unconventional vortex state.

cond-mat.supr-con↗