Thermoelectricity as a sensitive probe of the electronic structure of solids

Under the effect of a thermal gradient, the electrons in a solid produce an electric field. In the presence of a magnetic field, this electric field has a transverse component. These two effects, Seebeck and Nernst, are a valuable source of information on the organization of electrons in the solid in question. There are physical phenomena that have large-scale thermoelectric signatures. The Kondo effect is a case in point: the presence of a minute concentration of iron impurities in gold alters all the transport properties of the system at low temperatures. But while electrical resistivity rises by a few percent, the Seebeck coefficient amplifies by an order of magnitude. We will review a few cases of the use of this sensitive, but still poorly understood, probe of electron organization in solids. In highly correlated systems, thermoelectric effects document the birth of heavy electrons at low temperatures and their tumultuous life under magnetic fields. In dilute metals, the Nernst effect presents giant quantum oscillations under strong magnetic fields. The profile of these oscillations depends on the dimensionality of the system, as illustrated by the contrast between graphite and graphene. This sensitivity makes the Nernst effect an excellent fermiological tool. In particular, it has been used to establish the structure of the smallest Fermi surface that crosses a superconducting instability.