A new theoretical study by Cnr Nano researchers proposes an unconventional strategy to enhance thermoelectricity in nanoscale systems by exploiting spin-related effects rather than quantum confinement alone. The paper, “Enhanced thermoelectricity in nanowires with inhomogeneous helical states”, published in Physical Review Research, is authored by Zahra Aslani, Fabio Taddei and Alessandro Braggio (NEST, Cnr Nano and Scuola Normale Superiore), together with Fabrizio Dolcini (Politecnico di Torino).
Enhancing thermoelectricity — the direct conversion of heat into electricity — is a key challenge for recovering waste heat at room temperature and for heat management in quantum technologies. While quantum confinement in nanostructures is a well-established route to boost thermoelectric performance, the study demonstrates that manipulating Rashba spin–orbit interaction in helical nanowires can provide an alternative and powerful mechanism.
Helical systems are peculiar electronic states in which electrons with opposite spin propagate in opposite directions, a behavior typically associated with topological insulators. The research team shows that semiconducting nanowires with strong spin–orbit coupling under orthogonal magnetic fields can emulate such states. “By analyzing a junction between two nanowires with opposite spin–orbit orientations, we exploited the so-called Dirac paradox — usually known for suppressing transport — and turned it into an advantage”, explains Alessandro Braggio. Simply by controlling the relative rotation angle between the two spin–orbit fields, the team predicts a significant enhancement of thermoelectric properties.
“Our results show a completely novel way to enhance thermoelectricity purely by acting on the spin degree of freedom and on the helical nature of electronic states,” continues Braggio. “We have found an alternative route to quantum confinement, combining spin–orbit interaction and magnetic fields to boost thermoelectric response even at extremely low temperatures.”
Beyond suggesting new strategies to improve the efficiency of thermoelectric materials, the findings may inspire novel spin-based sensors and innovative approaches to harvest or manage heat at cryogenic temperatures — a crucial aspect for emerging quantum technologies. Future research will explore how thermoelectric effects behave in hybrid helical systems hosting Majorana fermions in the presence of superconductivity.
“Understanding the physics of small systems can open new solutions to global challenges,” Braggio adds. “From energy harvesting to the growing demand of AI-driven technologies, nanoscale quantum physics may help address some of the most pressing energy issues of our time.”
The study was carried out in the framework of the PNRR project NEThEQS. It also involved a researcher supported through a collaboration between ICTP and the QTHERMONANO project.
Reference article [freely available in Open Access]: Enhanced thermoelectricity in nanowires with inhomogeneous helical states, Zahra Aslani, Fabio Taddei, Fabrizio Dolcini, Alessandro Braggio, Phys. Rev. Research 8, 013175, 2026, DOI: https://doi.org/10.1103/mz9c-272x
