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Lee M.,Kyung Hee University | Lopez R.,University of the Balearic Islands | Lopez R.,Institute Of Fisica Interdisciplinar I Of Sistemes Complexos Ifisc Csic Uib | Choi M.-S.,Korea University | Martin T.,Aix - Marseille University
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We investigate nonperturbatively the charge relaxation resistance and quantum capacitance in a coherent RC circuit in the strong-coupling regime. We find that the many-body correlations break the universality in the charge relaxation resistance: (i) The charge relaxation resistance has peaks at finite frequencies Γ*/, where Γ* is an effective level broadening, and (ii) the zero-frequency resistance deviates from the universal value when the Zeeman splitting is comparable to Γ*. This behavior becomes even more prominent in the Kondo regime. The observed features are ascribed to the generation of particle-hole excitations in the contacts accomplished by spin-flip processes in the dot. © 2011 American Physical Society. Source


Huang S.M.,RIKEN | Huang S.M.,National Sun Yat - sen University | Badrutdinov A.O.,RIKEN | Badrutdinov A.O.,Kazan Federal University | And 10 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We study the spin-splitting energies in low-potential-barrier quantum dots, finding splitting energies that are orbital state dependent. The theoretical analysis is done with a generalization of the Fock-Darwin states in the presence of spin-orbit interactions. We discuss experimental evidence indicating that the Rashba interaction strength in vertical InxGa1-xAs/ GaAs quantum dots is in the range 80 meV Å ≤λR≤ 120 meV Å. This enhanced spin-orbit interaction can be understood from the high penetration of the electron wave function into the quantum well with low-potential barrier. © 2011 American Physical Society. Source


Kim B.-K.,Korea Research Institute of Standards and Science | Kim B.-K.,Chonbuk National University | Ahn Y.-H.,Korea Research Institute of Standards and Science | Ahn Y.-H.,Korea University | And 8 more authors.
Physical Review Letters | Year: 2013

We report nonequilibrium transport measurements of gate-tunable Andreev bound states in a carbon nanotube quantum dot coupled to two superconducting leads. In particular, we observe clear features of two types of Kondo ridges, which can be understood in terms of the interplay between the Kondo effect and superconductivity. In the first type (type I), the coupling is strong and the Kondo effect is dominant. Levels of the Andreev bound states display anticrossing in the middle of the ridge. On the other hand, crossing of the two Andreev bound states is shown in the second type (type II) together with the 0-π transition of the Josephson junction. Our scenario is well understood in terms of only a single dimensionless parameter, kBTKminâ¡ /Δ, where TKminâ¡ and Δ are the minimum Kondo temperature of a ridge and the superconducting order parameter, respectively. Our observation is consistent with measurements of the critical current, and is supported by numerical renormalization group calculations. © 2013 American Physical Society. Source


Lee M.,Kyung Hee University | Lim J.S.,Institute Of Fisica Interdisciplinar I Of Sistemes Complexos Ifisc Csic Uib | Lopez R.,Institute Of Fisica Interdisciplinar I Of Sistemes Complexos Ifisc Csic Uib | Lopez R.,University of the Balearic Islands
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

We investigate the dynamical and transport features of a Kondo dot side coupled to a topological superconductor (TS). The Majorana fermion states (MFSs) formed at the ends of the TS are found to be able to alter the Kondo physics profoundly: For an infinitely long wire where the MFSs do not overlap (εm=0) a finite dot-MFS coupling (Γm) reduces the unitary-limit value of the linear conductance by exactly a factor 3/4 in the weak-coupling regime (ΓmTK), on the other hand, the spin-split Kondo resonance takes place due to the MFS-induced Zeeman splitting, which is a genuine many-body effect of the strong Coulomb interaction and the topological superconductivity. We find that the original Kondo resonance is fully restored once the MFSs are strongly hybridized (εm>Γ m). This unusual interaction between the Kondo effect and the MFS can thus serve to detect the Majorana fermions unambiguously and quantify the degree of overlap between the MFSs in the TS. © 2013 American Physical Society. Source


Gelabert M.M.,University of the Balearic Islands | Serra L.,University of the Balearic Islands | Serra L.,Institute Of Fisica Interdisciplinar I Of Sistemes Complexos Ifisc Csic Uib
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We present calculations of the g factors for the lower conductance steps of three-dimensional hole quantum wires. Our results prove that the anisotropy with magnetic field orientation, relative to the wire, originates in the Rashba spin-orbit coupling. We also analyze the relevance of the deformation, as the wire evolves from three-dimensional toward a flat two-dimensional geometry. For high enough wire deformations, the perpendicular g factors are greatly quenched by the Rashba interaction. On the contrary, parallel g factors are rather insensitive to the Rashba interaction, resulting in a high g-factor anisotropy. For low deformations, we find a more irregular behavior, which hints at a sample-dependent scenario. © 2011 American Physical Society. Source

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