Thermoelectric Properties In Low-dimensional Quantum Materials

Thermoelectric conversion technology is a new and environment-friendly energy conversion technology with wide application prospect.However,the conversion efficiency of thermoelectric materials is too low to applied to the actual.Recently,people found that the topological insulators have excellent thermoelectric conversion ability.Therefore,the study of the thermoelectric properties of new topological insulator materials can help us understand the material better,and provide important reference to the subsequent development of thermoelectric devices.In this paper,we studied the thermoelectric properties of Sb₂H/LaFeO₃ heterostructure and Z₂=0 topological insulator,by using the tight binding model combined with non-equilibrium Green function method and Landauer-Büttiker transport theory.Firstly,the thermoelectric properties of Sb₂H/LaFeO₃ heterostructure under different topological phases were studied.The width of the band gap varies with the topological phase of the material.We find that the narrower the bulk gap is,the worse the thermoelectric conversion efficiency is.However,the thermoelectric conversion capability of the material with narrow gap is better at low temperature.In addition,the thermoelectric properties of Sb₂H/LaFeO₃ heterostructure with a novel quantum spin-quantum Hall effect was specially studied.We found that the thermoelectric properties of the system can be manipulated through tuning the exchange fields of the outmost sublattice or varying the geometric size of the sample.The increase of edge state reduces the Seebeck coefficient of the system,thus reducing the thermoelectric conversion ability,especially at low temperatures.Moreover,with the increase of the width of the sample increases the Seebeck coefficient of the system,so that the system has better thermoelectric conversion capability.At the end,the thermoelectric properties of Z₂=0 topological insulator was investigated,we found that the performance of the thermoelectric properties of the system is similar as other topological insulators,but it is not a good thermoelectric materials.Moreover,we found that the Seebeck coefficient is less affected by temperature.In addition,we also found that the disordered will reduce the Seebeck coefficient of this material system,thereby reducing the thermoelectric conversion ability.Increasing the size of the sample does not improve its thermoelectric conversion capability as other two-dimensional topological insulator materials.