Negative differential thermal conductance by photonic transport in electronic circuits

TL;DR

This paper demonstrates how electromagnetic heat transfer in simple circuits can exhibit negative differential thermal conductance, enabling thermal transistor functionalities at the nanoscale, especially using superconductor-resistive phase transitions.

Contribution

It introduces a practical framework for engineering NDTC through impedance matching in electromagnetic heat transfer circuits, with a case study on superconductor-based structures.

Findings

NDTC occurs near impedance matching conditions in electromagnetic heat transfer.

A superconductor-resistive transition can induce a temperature drop of a few millikelvin.

The approach offers new pathways for nanoscale thermal transistor implementation.

Abstract

The negative differential thermal conductance (NDTC) provides the key mechanism for realizing thermal transistors. This exotic effect has been the object of an extensive theoretical investigation, but the implementation is still limited to a few specific physical systems. Here, we consider a simple circuit of two electrodes exchanging heat through electromagnetic radiation. We demonstrate that the existence of an optimal condition for power transmission, well-known as impedance matching in electronics, provides a natural framework for engineering NDTC: the heat flux is reduced when the temperature increase is associated to an abrupt change of the electrode's impedance. As a case study, we analyze a hybrid structure based on thin-film technology, in which the increased resistance is due to a superconductor-resistive phase transition. For typical metallic superconductors operating below $1$K, NDTC reflects in a temperature drop of the order of a few mK by increasing the power supplied to the system. Our work draws new routes for implementing a thermal transistor in nanoscale circuits.