Entropy transport in Bi$_{2}$Se$_{3}$

Bi$_2$Se$_3$ and Bi$_2$Te$_3$ are well known compounds in the thermoelectricity community as they present a high figure of merit [1]. Although the thermoelectric power of Bi$_2$Se$_3$ has been extensively studied at high temperature, little is known about its behaviour at the low temperature limit. In this presentation, we will report the results of our entropy measurement of Bi$_{2}$Se$_{3}$ at low temperature and high magnetic field for a bulk carrier concentration from 10$^{17}$cm$^3$ to 10$^{19}$cm$^3$. In all compounds we show significant quantum oscillations in the Seebeck and Nernst responses. Based on the bulk Fermi surface, we propose a simple description of the entropy transport measurement in Bi$_2$Se$_3$ (in the range of concentrations studied). Indeed, Bi$_2$Se$_3$ (non compensated system) appears as a complementary system of bismuth [2] and graphite [3] (compensated systems) to understand the entropy transport in the low carrier concentration limit. \\[4pt] [1] G.S. Nolas et al, Thermoelectrics Basic Principles and New Materials Developments, Springer.\\[0pt] [2] K.Behnia et al, PRL, 98, 166602 (2007)\\[0pt] [3] Z.Zhu et al, Nature Physics, 6, 26 (2009)