F. Lisandrini | Searcharxiv

arXiv2019

Influence of Rashba spin-orbit coupling on the 0-$π$ transition and Kondo temperature in 1D superconductors

Using the framework of the density-matrix renormalization group (DMRG), we study a quantum dot coupled to a superconducting nanowire with strong Rashba spin-orbit coupling. Regarding the singlet-to-doublet "0-$π$" transition that takes place when the Kondo effect is overcome by the superconducting gap, we show that the Rashba coupling modifies the critical values at which the transition occurs, favouring the doublet phase. In addition, using a generalized Haldane's formula for the Kondo temperature $T_K$, we show that it is lowered by the Rashba coupling. We benchmark our DMRG results comparing them with previous numerical renormalization group (NRG) results. The excellent agreement obtained opens the possibility of studying chains or clusters of impurities coupled to superconductors by the means of DMRG.

cond-mat.str-el↗

arXiv2017

Width of the charge-transfer peak in the SU(N) impurity Anderson model and its relevance to non-equilibrium transport

We calculate the width $2Δ_{\text{CT}}$ and intensity of the charge-transfer peak (the one lying at the on-site energy $E_d$) in the impurity spectral density of states as a function of $E_d$ in the SU($N$) impurity Anderson model (IAM). We use the dynamical density-matrix renormalization group (DDMRG) and the noncrossing-approximation (NCA) for $N$=4, and a 1/$N$ variational approximation in the general case. In particular, while for $E_d \gg Δ$, where $Δ$ is the resonant level half-width, $Δ_{\text{CT}}=Δ$ as expected in the noninteracting case, for $-E_d \gg N Δ$ one has $Δ_{\text{CT}}=NΔ$. In the $N$=2 case, some effects of the variation of $% Δ_{\text{CT}}$ with $E_d$ were observed in the conductance through a quantum dot connected asymmetrically to conducting leads at finite bias [J. Könemann \textit{et al.}, Phys. Rev. B \textbf{73}, 033313 (2006)]. More dramatic effects are expected in similar experiments, that can be carried out in systems of two quantum dots, carbon nanotubes or other, realizing the SU(4) IAM.

cond-mat.str-el↗