In this talk, we will discuss the efficiency of thermoelectric conversion in doped semiconductor nanowires equipped with a gate allowing the carrier density to be varied. We will first show old experimental results by M. Sanquer and co-workers [1], which indicate the interest of moving towards the edges of the impurity band when taking nanowires at very low temperature (elastic regime where quantum transport remains coherent). We will then present recent theoretical results [2] describing thermoelectric conversion in this regime for disordered chains where the electronic states are localized. The typical Seebeck coefficient and its sample-to-sample fluctuations will be given, from the center of the impurity band to its edges. In the same elastic regime, we will then describe the Seebeck coefficient distribution for cavities with chaotic classical dynamics [3, 4]. We'll see that these distributions are universal and differ depending on whether the Fermi energy probes the core or the edges of the cavity spectrum. Finally, we will consider disordered nanowires in an intermediate temperature regime where transport becomes inelastic and activated (variable range jump Mott regime). Using recent work by Y. Imry and co-workers [5] on electron glasses, we will see that the interest in moving towards the edges of the impurity band remains in the activated regime. Finally, we will show that recent measurements by P. Kim's group [6] at Columbia in silicon and germanium/silicon nanowires confirm that this interest remains at room temperature.
10:45 - 11:45
Seminar
Low-temperature thermoelectric conversion in disordered nanowires and chaotic quantum cavities : the interest of spectral edges
Jean-Louis Pichard
