Nernst effect

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 ${\displaystyle \nu }$, which is defined to be

${\displaystyle \nu ={\frac {E_{y}}{B_{z}}}{\frac {1}{\partial _{x}T}}}$

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

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.^{[1][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.^[2][3][4] High-temperature superconductors exhibit the Nernst effect both in the superconducting and in the pseudogap phase.^[5] Heavy fermion superconductors can show a strong Nernst signal which is likely not due to the vortices.^[6]

See also

• Spin Nernst effect
• Seebeck effect
• Peltier effect
• Hall effect
• Righi–Leduc effect

References