arXiv subjects

Juan Pablo Ramos-Andrade

Publications and source records attributed to Juan Pablo Ramos-Andrade.

4 recordsLinked to original sources

arXiv2026

Shot noise signatures of Majorana-assisted transport in an Aharonov-Bohm interferometer

In this work, we investigate the finite-bias charge current, shot noise, and Fano factor in an Aharonov-Bohm interferometer composed of two parallel quantum dots, each side-coupled to a topological superconducting nanowire represented by an effective Kitaev chain hosting Majorana bound states at its ends. The transport properties are calculated using the nonequilibrium Green's function formalism within the equation-of-motion approach. Our results show that coupling to the Majorana bound states significantly modifies the interference pattern, producing distinctive signatures in the current, shot noise, and Fano factor. These signatures are particularly pronounced at the half-flux condition, where destructive interference suppresses the conventional transport background and enhances the visibility of Majorana-assisted transport. These findings demonstrate that finite-bias shot-noise spectroscopy provides a sensitive indirect probe of Majorana bound states in hybrid superconducting-nanowire interferometers.

cond-mat.mes-hall↗

arXiv2026

An improved auxiliary boson method for quantum dots with finite Coulomb interaction U

In this work, we present an improved version of the formulation of the four auxiliary bosons originally proposed by Kotliar and Ruckenstein, adapted to describe a quantum dot in the Kondo regime with finite electron-electron interaction U. The proposed refinement provides a more accurate treatment of strong electronic correlations while preserving the analytical tractability of the original approach, thereby enabling a reliable description of transport properties in nanoscale systems. Benchmark calculations show good agreement with the results of the numerical renormalization group, supporting the validity of the improved formulation. Our approach therefore provides an efficient and robust framework for investigating transport through strongly correlated quantum dots.

cond-mat.mes-hall↗

arXiv2026

Phase-controlled quasi-bound states in the continuum and thermoelectric enhancement in Majorana-quantum-dot nanostructures

We investigate how the interplay between Majorana zero modes (MZMs) and bound states in the continuum (BICs) governs the electronic thermoelectric response of a crossbar-shaped quantum dot (QD) coupled to two topological-superconductor nanowires. Using the Green-function formalism, exact linear-response energy integrals, and their low-temperature Sommerfeld expansion, we analyze the spectral and thermoelectric properties of the system. We show that symmetry breaking converts BICs into quasi-BICs, allowing them to contribute to electrical and thermal transport and thereby generate a finite thermoelectric response. While unequal nanowire lengths, reflected in different intra-Majorana coupling strengths, produce only a modest enhancement of $ZT_{el}$, detuning the QD level increases $ZT_{el}$ by approximately one order of magnitude. Superconducting-phase control produces a much stronger enhancement, reaching $ZT_{el} \simeq 0.75$ through a quadratic transmission zero and a pronounced violation of the Wiedemann-Franz law. The low-temperature values $ZT^{max}_{el} \simeq 0.755$ and $\mathscr{L} /\mathscr{L}_{0} = 21/5$ are universal consequences of this quadratic antiresonance. Our results establish phase-tunable thermoelectric signatures of the Majorana-coupled interference structure and identify superconducting-phase control as an efficient means of engineering the electronic response of topological hybrid nanostructures.

cond-mat.mes-hall↗

arXiv2022

Bound states in the continuum in a two-channel Fano-Anderson model

In this article, we study the formation of the bound states in the continuum (BICs) in a two-channel Fano-Anderson model. We employ the Green's function formalism, together with the equation of motion method, to analyze the relevant observables, such as the transmission coefficient and the density of states. Most importantly, our results show that the system hosts true BICs for the case of a symmetric configuration with the degenerate impurity levels, and a complete transmission channel is then suppressed. Finally, we argue that the proposed mechanism could be relevant for the realization of BICs in the electronic and photonic systems.

cond-mat.mes-hall↗