$\Delta_T$ Noise from Electron-Hole Asymmetry in Normal and Superconducting Quantum Point Contacts

TL;DR

This paper investigates how electron-hole asymmetry in quantum point contacts affects $ abla_T$ noise and thermovoltage in hybrid nanostructures, revealing the role of Andreev reflection in non-equilibrium charge fluctuations.

Contribution

It provides the first self-consistent analysis of $ abla_T$ noise in superconducting hybrid junctions with broken electron-hole symmetry, highlighting the impact of Andreev reflection.

Findings

Broken e-h symmetry leads to finite thermovoltage.

Andreev reflection significantly modifies $ abla_T$ noise.

Established a self-consistent framework for mesoscopic hybrid junctions.

Abstract

This work examines $\Delta_T$ noise in two-terminal hybrid nanostructures featuring a quantum point contact (QPC), realized either between two normal metals (NQN) or between a normal metal and a superconductor (NQS). The inclusion of a QPC breaks electron-hole (e-h) symmetry, leading to a finite thermovoltage. In contrast, earlier studies on hybrid junctions incorporating insulating barriers, as e-h symmetry is preserved, have vanishing thermovoltage, and consequently, $\Delta_T$ noise is calculated at zero thermovoltage. In our setup, the broken e-h symmetry allows for a finite thermovoltage, at which we compute the corresponding $\Delta_T$ noise. Unlike earlier studies restricted by e-h symmetry and vanishing thermovoltage, our work establishes a self-consistent framework in mesoscopic hybrid junctions, revealing how Andreev reflection fundamentally reshapes $\Delta_T$ noise once e-h symmetry is broken. This broad access to charge fluctuation signatures provides a more comprehensive understanding of non-equilibrium transport in linear response. To our knowledge, this work provides the first self-consistent analysis of $\Delta_T$ noise in superconducting hybrid junctions where e-h symmetry is broken, explicitly revealing how Andreev reflection modifies $\Delta_T$ noise beyond the symmetry-protected zero-thermovoltage regime.