In physics and chemistry, the Nernst effect (also termed first Nernst–Ettingshausen effect, after Walther Nernst and Albert von Ettingshausen) is a thermoelectric (or thermomagnetic) phenomenon observed when a sample allowing electrical conduction is subjected to a magnetic field and a temperature gradient normal (perpendicular) to each other. An electric field will be induced normal to both.
This effect is quantified by the Nernst coefficient , which is defined to be
where is the y-component of the electric field that results from the magnetic field's z-component and the x-component of the temperature gradient .
The reverse process is known as the Ettingshausen effect and also as the second Nernst–Ettingshausen effect.
Mobile energy carriers (for example conduction-band electrons in a semiconductor) will move along temperature gradients due to statistics[dubious ] and the relationship between temperature and kinetic energy. If there is a magnetic field transversal to the temperature gradient and the carriers are electrically charged, they experience a force perpendicular to their direction of motion (also the direction of the temperature gradient) and to the magnetic field. Thus, a perpendicular electric field is induced.
Semiconductors exhibit the Nernst effect. This has been studied in the 1950s by Krylova, Mochan and many others. In metals however, it is almost non-existent. It appears in the vortex phase of type-II superconductors due to vortex motion. This has been studied by Huebener et al. High-temperature superconductors exhibit the Nernst effect both in the superconducting and in the pseudogap phase, as was first found by Xu et al. Heavy-Fermion superconductors can show a strong Nernst signal which is likely not due to the vortices, as was found by Bel et al.