2026/07/17 by Alejandro Garrido, David Zambrano, Hishan Farfán-Bachiloglu +3
#cond-mat.mes-hall
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 ZTel, detuning the QD level increases ZTel by approximately one order of magnitude. Superconducting-phase control produces a much stronger enhancement, reaching ZTel ≃ 0.75 through a quadratic transmission zero and a pronounced violation of the Wiedemann-Franz law. The low-temperature values ZTmaxel ≃ 0.755 and \mathscrL /\mathscrL0 = 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.