Principal Investigator :

Cyril Proust ()
LNCMI (FFC)

Type of project : Disruptive Project

Date (start/end) : 2018 - 2020

   

Sample contacted for thermoelectric measurements. 

 

Abstract

In thermoelectric measurements a thermal gradient is generated across the length of the sample, which results in a longitudinal voltage (thermoelectric power) and a transverse voltage (Nernst effect) in presence of a magnetic field. While the thermoelectric power is directly related to the Fermi temperature and carrier type (hole or electron like), the Nernst effect holds information on the carrier mobility of the system. The measurement of the thermoelectric power is a useful and sensitive tool to probe the Fermi surface. It has been used to detect Fermi surface reconstruction by charge density wave in underdoped cuprate [1]. In the heavy fermions URu ₂ Si ₂ , a change in the Fermi surface has been detected in the so-called \\\'hidden order\\\' phase using high field measurements of TEP [2]. At low temperature, a linear low-temperature dependence of thermoelectric power, much like the T ² -behavior of the resistivity, can be interpreted as a hallmark of Fermi liquid behavior. Deviations from this behavior is consequently considered as a signature of unusual, so-called non-Fermi-liquid physics found in the vicinity of quantum phase transitions.

We propose to build a novel and unique setup to measure thermoelectric power and the Nernst effect in pulsed magnetic fields up to 100 T. The primary motivation is to measure the thermoelectric power in overdoped cuprates with their superconductivity quenched by high magnetic field. Through this, we will be able to deduce the doping ( p ) dependence of the effective mass and test whether the opening of the pseudogap at p ^* corresponds to a quantum critical point or to the opening of a gap associated with the vanishing of an energy scale. The use of this setup for the study of other correlated electron systems, such as pnictide superconductors, heavy fermions, topological insulators is also envisaged.

 

References:

[1] Laliberté F. et al. Nature Comm. 2 432 (2011).

[2] Malone L. et al. Physical Review B 83 245117 (2011).