In physics and chemistry, the Nernst effect (also termed first Nernst–Ettingshausen effect, after
Walther Nernst and
Albert von Ettingshausen) is a
thermoelectric
The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa via a thermocouple. A thermoelectric device creates a voltage when there is a different temperature on each side. Conversely, when ...
(or thermomagnetic) phenomenon observed when a sample allowing
electrical conduction
Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allows ...
is subjected to a
magnetic field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and t ...
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 , ''N'', , 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 temperature gradient
.
The reverse process is known as the
Ettingshausen effect and also as the second Nernst–Ettingshausen effect.
Physical picture
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energy carriers (for example
conduction-band electron
The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family,
and are generally thought to be elementary partic ...
s in a
semiconductor
A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. ...
) will move along
temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer.
Thermometers are calibrated in various temperature scales that historically have relied on ...
gradients due to statistics and the relationship
between temperature and kinetic energy. If there is a
magnetic field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and t ...
transversal to the temperature gradient and the carriers are
electrically charged, they experience a
force
In physics, a force is an influence that can change the motion of an object. A force can cause an object with mass to change its velocity (e.g. moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a ...
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
Semiconductors exhibit the Nernst effect. This has been studied in the 1950s by Krylova, Mochan and many others. In
metal
A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typi ...
s 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
In solid-state physics, heavy fermion materials are a specific type of intermetallic compound, containing elements with 4f or 5f electrons in unfilled electron bands. Electrons are one type of fermion, and when they are found in such materials, th ...
superconductors can show a strong Nernst signal which is likely not due to the vortices, as was found by Bel et al.
See also
*
Seebeck effect
The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa via a thermocouple. A thermoelectric device creates a voltage when there is a different temperature on each side. Conversely, when ...
*
Peltier effect
The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa via a thermocouple. A thermoelectric device creates a voltage when there is a different temperature on each side. Conversely, when ...
*
Hall effect
The Hall effect is the production of a voltage difference (the Hall voltage) across an electrical conductor that is transverse to an electric current in the conductor and to an applied magnetic field perpendicular to the current. It was disc ...
*
Righi–Leduc effect
Journal articles
* R. P. Huebener and A. Seher, "Nernst Effect and Flux Flow in Superconductors. I. Niobium"
Web* R. P. Huebener and A. Seher, "Nernst Effect and Flux Flow in Superconductors. II. Lead Films"
Web* V. A. Rowe and R. P. Huebener, "Nernst Effect and Flux Flow in Superconductors. III. Films of Tin and Indium"
Web*
*
*{{Cite journal , last1=Krylova , first1=T. V. , last2=Mochan , first2=I. V. , journal=J. Tech. Phys. (USSR) , volume=25 , pages=2119 , year=1955
Walther Nernst
Electrodynamics
Thermoelectricity