Alicja Kawala | Searcharxiv

arXiv2024

Topological properties of the [110] SnTe nanowires

SnTe materials are know to be a platform for realization of various strong and symmetry protected topological phases in one, two and three spatial dimensions. We study symmetry-protected topological states in $[110]$ SnTe nanowires in the presence of various combinations of Zeeman field, $s-$wave superconductivity, inversion-symmetry-breaking field and the thickness of the wire. In the normal state we find a Weyl semimetal phase protected by a twofold screw axis symmetry and a topological insulating phase characterized by a $\mathbb{Z}$ invariant protected by a mirror symmetry. In the presence of superconductivity, we find inversion-symmetry-protected gapless phase which becomes fully gapped and topologically non-trivial by introducing an inversion-symmetry-breaking field. Consequently, we find topologically protected localized Majorana zero modes appear at the ends of the wire. We find that this Majorana phase is much easier to achieve in a $[110]$ SnTe nanowire than in a $[001]$ one.

cond-mat.mes-hall↗

arXiv2023

Superconductivity near the Mott-Ioffe-Regel limit in the high-entropy alloy superconductor (ScZrNb)$_{1-x}$(RhPd)$_x$ with a CsCl-type lattice

Theoretical analysis of the electronic structure of the high-entropy-type superconductor (ScZrNb)$_{1-x}$(RhPd)$_x$, $x \in (0.35, 0.45)$ is presented. The studied material is a partially ordered CsCl-type structure, with two sublattices, randomly occupied by Sc, Zr, Nb (first sublattice) and Nb, Rh, and Pd (second sublattice). Calculations were done using the Korringa-Kohn-Rostoker method with the coherent potential approximation (KKR-CPA) and take into account the substitutional disorder. Our total energy calculations confirm the preference for the partially ordered structure over the fully random {\it bcc}-type one. Electronic densities of states $N(E)$, dispersion relations, and McMillan-Hopfield parameters $η$ (electronic contribution to electron-phonon coupling) are studied as a function of composition. The computed increasing trends in $N(E_F)$ and $η$ with $x$ are opposite to what we expected based on the experimental results, where the decrease in the critical temperature with increasing $x$ was found. Very strong electron scattering due to disorder is observed, as the electronic dispersion relations are strongly smeared. As a result, the computed electronic lifetimes $τ$ are very short, leading to a small mean-free path of electrons of the order of interatomic distance, which puts (ScZrNb)$_{1-x}$(RhPd)$_x$ near the Mott-Ioffe-Regel limit. The trend in $τ(x)$ is similar to the trend observed experimentally in $T_c(x)$, suggesting that disorder may be the factor that influences $T_c$ in this series of alloys.

cond-mat.supr-con↗