Setup for energy-harvesting experiment. Credit: Communications Physics (2025). DOI: 10.1038/s42005-025-02297-6

Touch the back of a laptop and it often feels warm. This is because part of the energy used for computation and communication escapes to the outside as heat. Yet even this "waste heat" still contains a great deal of usable energy. Technologies that convert such waste heat into electricity for reuse are known as energy harvesting.

Classical and quantum approaches to waste heat

Conventional energy-harvesting technologies have been developed within the framework of classical thermodynamics. In classical thermodynamics, a heat source is typically assumed to be in thermal equilibrium—a stable state in which temperature becomes uniform and heat flow is minimal.

However, as waste heat approaches thermal equilibrium, the amount of energy that can be reused decreases, and consequently the amount that can be extracted as electricity also diminishes.

For this reason, researchers have focused on non-thermal states, special quantum states that do not settle into thermal equilibrium. Non-thermal states have been realized in various ways—for example, in atoms whose temperature distribution is controlled by lasers, or in coherent atomic ensembles (special states in which many atoms behave in synchrony, following the same rhythm).

In many cases, however, creating these non-thermal states requires highly precise control, making practical applications to energy recovery challenging.

The promise of Tomonaga–Luttinger liquids

In recent years, a promising candidate has attracted increasing attention: the Tomonaga–Luttinger (TL) liquid. A TL liquid refers to a special state in which electrons are confined to a narrow channel and move collectively while strongly influencing one another. Rather than behaving independently, the electrons flow in a coordinated manner reminiscent of a liquid—hence the name.

In TL liquids, electronic energy does not readily relax into thermal equilibrium, and non-thermal states can be sustained naturally. This has led to expectations that TL liquids could be useful for energy harvesting, but it had remained unclear whether they are truly advantageous for thermoelectric conversion.

Experimental breakthrough and findings

A research team led by Professor Toshimasa Fujisawa of Institute of Science Tokyo (Science Tokyo) has now provided the world’s first clear experimental evidence addressing this question. In their study www.nature.com="" articles="" s42005-025-02297-6"="">published</a> in the journal Communications Physics, the team fabricated a compact energy-harvesting device that utilizes a naturally occurring non-thermal state (the NT state) in a TL liquid, and compared its ability to convert heat into electricity with that of a state close to thermal equilibrium (the QT state).

The results showed that, when the same amount of heat was supplied, the voltage generated in the NT state was approximately two to three times higher than that in the QT state. The team also confirmed that the conversion efficiency from heat to electricity was consistently higher in the NT state.

Why non-thermal states are advantageous

The key to understanding why the NT state is advantageous lies in how electronic energy is distributed. Analysis revealed that, in the NT state, electrons exhibit a distribution in which high-energy and low-energy populations coexist while maintaining disorder (entropy). In other words, instead of relaxing uniformly as in thermal equilibrium, a prominent population of high-energy electrons remains—making it easier to extract electrical energy.

Implications and future directions

This achievement marks a major advance in technologies that convert waste heat into electricity. Potential applications include large-scale recovery of exhaust heat in factories and data centers, self-powered operation of compact electronic devices, energy-saving technologies in extremely low-temperature environments, and extensions to other quantum systems and integrable systems.

Output power may also be increased by refining the design of energy filters that selectively extract the "high-energy side" of the non-thermal state. More broadly, this concept is expected to be applicable to other quantum systems and to a range of material systems that do not readily relax into thermal equilibrium.

The team has conducted experiments based on the belief that naturally emerging "non-thermal states" in the quantum world can achieve high thermal efficiency, but proving this was more difficult than we expected.

The team feel that the day is approaching when heat that is currently lost will become useful again through the power of quantum effects.

More information: Hikaru Yamazaki et al, Efficient heat-energy conversion from a non-thermal Tomonaga-Luttinger liquid, Communications Physics (2025). DOI: 10.1038/s42005-025-02297-6

Citation: A new approach to energy harvesting opened up by the quantum world (2026, January 18) retrieved 18 January 2026 from https://techxplore.com/news/2026-01-approach-energy-harvesting-quantum-world.html

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