In physics and chemistry, the Nernst effect (also termed the 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 ν {\displaystyle \nu }, which is defined to be

ν = E y B z 1 ∂ x T {\displaystyle \nu ={\frac {E_{y}}{B_{z}}}{\frac {1}{\partial _{x}T}}}

where E y {\displaystyle E_{y}} is the y-component of the electric field that results from the magnetic field's z-component B z {\displaystyle B_{z}} and the x-component of the temperature gradient ∂ x T {\displaystyle \partial _{x}T}.

The reverse process is known as the Ettingshausen effect and also as the second Nernst–Ettingshausen effect.

Physical picture

Mobile energy carriers (for example conduction-band electrons in a semiconductor) will move along temperature gradients due to statistics[dubious – discuss] 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.

Sample types

The semiconductors exhibit the Nernst effect, as first observed by T. V. Krylova and Mochan in the Soviet Union in 1955.[non-primary source needed] In metals however, it is almost non-existent.[citation needed]

Superconductors

Nernst effect appears in the vortex phase of type-II superconductors due to vortex motion. High-temperature superconductors exhibit the Nernst effect both in the superconducting and in the pseudogap phase. Heavy fermion superconductors can show a strong Nernst signal which is likely not due to the vortices.

See also