On the thermoelectricity of correlated electrons in the zero-temperature limit

The Seebeck coefficient of a metal is expected to display a linear temperature-dependence in the zero-temperature limit. To attain this regime, it is often necessary to cool the system well below 1K. We put under scrutiny the magnitude of this term in different families of strongly-interacting electronic systems. For a wide range of compounds (including heavy-fermion, organic and various oxide families) a remarkable correlation between this term and the electronic specific heat is found. We argue that a dimensionless ratio relating these two signatures of mass renormalisation contains interesting information about the ground state of each system. The absolute value of this ratio remains close to unity in a wide range of strongly-correlated electron systems.Comment: 15 pages, including two figure

Atomic scale engineering of superlattices and magnetic wires

In the past years artificially-structured materials have been grown with an increasing degree of sophistication due to steady progress in our ability to control growth processes down to the atomic level. These materials have yielded new physical properties due to the confinement of electrons in less than three dimensions. Thus, the confinement of electrons in two-dimensional (2D) metallic superlattices has resulted in oscillatory magnetic coupling with an associated oscillatory giant magnetoresistance (GMR). New properties are expected when the electrons are further confined to one dimension (1D) of free motion in the structures known as quantum wires. In this report we briefly describe two recent examples of atomic-scale engineering of materials. In the first case a surfactant is used to purposely modify the structure of magnetic/non magnetic superlattices. The second example illustrates a further reduction in dimensionality obtained by modifying the substrate onto which the growth takes place: the fabrication of 1D magnetic quantum wires on vicinal surfaces.Peer reviewe