A theoretical study carried out by researchers at Cnr Nano and Scuola Normale Superiore has unveiled a novel mechanism of quantum thermoelectricity, leading to a nonlinear bipolar thermoelectric response. Remarkably, the ultracold electromagnetic environment surrounding a superconducting device does not merely act as a passive background, but actively contributes to the generation of an electrical voltage. Published in npj Quantum Information, the work opens new perspectives for controlling energy transport in quantum devices operating at cryogenic temperatures.

Thermoelectricity is the phenomenon through which a temperature gradient is converted into electrical energy. In conventional materials, this effect originates from intrinsic asymmetries in charge transport properties, such as the different mobilities of electrons and holes, which redistribute unevenly under a thermal gradient and thereby generate an electric voltage.

The study, conducted by Alessandro Braggio, Giorgio De Simoni and Francesco Giazotto of Cnr Nano together with Filippo Antola of Scuola Normale Superiore, reveals a fundamentally different mechanism. The researchers investigated a superconducting tunnel junction, in which electrons cross an insulating barrier via quantum tunnelling. They demonstrated that, at temperatures approaching absolute zero, the surrounding electromagnetic environment can efficiently absorb energy from the device while exhibiting a strongly suppressed ability to return it.

“Essentially, the system responds differently depending on whether it emits or absorbs energy, and this asymmetry gives rise to an unexpected effect: heat can be converted into an electrical potential difference — namely a voltage — under conditions where, according to conventional thermoelectric theory, no such effect should occur,” explains Filippo Antola.

“The results further demonstrate that the quantum environment is not merely a passive background, but can actively shape the behaviour of the device. Thermoelectricity is therefore not generated solely by the material itself, but also by the quantum nature of its interaction with the surrounding environment,” adds Alessandro Braggio.

The study also offers a different perspective on the role of the environment in quantum devices. “In quantum technologies, the external environment has long been regarded primarily as a source of noise and information loss. Our work shows instead that, under suitable conditions, the quantum environment can become a resource for power generation, paving the way for devices in which the environment itself is engineered as a functional element,” Braggio concludes.

Although theoretical, the study may enable future applications including ultrasensitive thermal sensors and heat-management strategies in quantum circuits, where even extremely small energy variations can critically affect device performance.

Reference article: F. Antola, G. De Simoni, F. Giazotto, A. Braggio, Quantum bipolar thermoelectricity. npj Quantum Inf(2026). https://doi.org/10.1038/s41534-026-01237-8

[IMAGE: artistic rendering of the quantum thermoelectric process in a superconducting junction]