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A new quantum transport theory reveals how femtosecond time scale thermoelectric fluctuations influence energy control at the nanoscale. The University of Jyväskylä, Finland, has contributed to the development of a theoretical approach that enables accurate simulations of temperature differences and electric currents in nanoscale junctions formed by single molecules. The research opens new possibilities for designing components used in quantum technologies.

In the thermoelectric effect, a temperature difference generates electricity. A well-known example is the Seebeck effect, where a voltage arises between the ends of a material held at different temperatures. In the Peltier effect, which is a complementary phenomenon, an electric current causes one end of the material to heat up while the other cools down.

"The phenomenon is particularly interesting in electronics, where components continuously produce waste heat. If this heat could be converted back into useful electricity while simultaneously controlling overheating, devices could become significantly more energy-efficient, explains Senior Lecturer Riku Tuovinen from the University of Jyväskylä.

The results are in PRX Energy.

From theory to practice

A collaboration between researchers at the University of Jyväskylä and Wroclaw University of Science and Technology reveals how temperature differences and electric currents behave in nanoscale junctions formed by single molecules, when the electrons are not in equilibrium but oscillate back and forth in time.

To describe this behavior, a new approach to time-dependent quantum transport theory was developed, allowing the study of nanoscale structures where simple models fail to capture the multifaceted quantum effects. The theory has already been implemented in the CHEERS computational software, enabling detailed simulations of nanoscale thermoelectric processes.

"Our theoretical results show that molecular junctions can exhibit ultrashort periods during which the efficiency of thermoelectric conversion surpasses the steady-state level, says Tuovinen. Such brief efficiency peaks demonstrate that a dynamical view of the thermoelectric effect is crucial for both understanding nanoscale processes and advancing future quantum and energy technologies," he continues.

Nanoscale energy management requires a deep understanding of quantum dynamics

The study shows that femtosecond time scale thermoelectric fluctuations in molecular junctions can open new opportunities for controlling energy flow in nanoscale components.

"This is particularly relevant for future technologies, for example in developing ultrafast bolometers used for qubit readout in quantum computers," adds Tuovinen.

The research highlights that understanding time-dependent quantum phenomena is essential for harnessing heat transfer in nanoscale systems.