Electrically tunable giant Nernst effect in two-dimensional van der Waals heterostructures

The Nernst effect, a transverse thermoelectric phenomenon, has attracted significant attention for its potential in energy conversion, thermoelectrics and spintronics. However, achieving high performance and versatility at low temperatures remains elusive. Here we demonstrate a large and electrically tunable Nernst effect by combining the electrical properties of graphene with the semiconducting characteristics of indium selenide in a field-effect geometry. Our results establish a new platform for exploring and manipulating this thermoelectric effect, showcasing the first electrical tunability with an on/off ratio of 103. Moreover, photovoltage measurements reveal a stronger photo-Nernst signal in the graphene/indium selenide heterostructure compared with individual components. Remarkably, we observe a record-high Nernst coefficient of 66.4 μV K−1 T−1 at ultralow temperatures and low magnetic fields, an important step towards applications in quantum information and low-temperature emergent phenomena.

The investigation of thermoelectricity traces its origins back to the mid-nineteenth century when Lord Kelvin embarked on a quest to comprehend it as a quasi-thermodynamic phenomenon. A notable milestone in this journey occurred in 1931 with the formulation of reciprocal relations by Onsager1. Such relations established crucial connections, including the Kelvin relation between Seebeck and Peltier coefficients and the Bridgman relation linking the Nernst and Ettingshausen effects2. Practical applications, however, have been limited to date. Nevertheless, recent technological advancements and promising applications in energy conversion, thermoelectrics and spintronics have renewed interest in thermoelectric phenomena3,4,5,6,7. One such effect is the Nernst–Ettingshausen effect, which manifests itself as a transverse electric field, known as the Nernst voltage, generated by the Lorentz force acting on charge carriers in the presence of a temperature gradient and a magnetic field. Among the recently investigated materials, topological semimetals show promise for efficient thermoelectric cooling via the Nernst–Ettingshausen effect3,8. Such materials are characterized by zero or slight band overlap, and high carrier mobilities that are beneficial for enhancing thermoelectric effects. On the other hand, difficulties in measuring the transverse thermoelectric effects have slowed down the progress compared with its longitudinal counterpart9,10,11,12, despite extensive work on reaching high thermoelectric figures of merit3,5,6.

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