Title:	topological and thermoelectrical materials
DNr:	SNIC 2022/22-1112
Project Type:	SNIC Small Compute
Principal Investigator:	Ali Sufyan <ali.sufyan@associated.ltu.se>
Affiliation:	Luleå tekniska universitet
Duration:	2022-11-15 – 2023-12-01
Classification:	10304
Keywords:

Abstract

Topological insulators have sparked numerous theoretical and experimental studies on various topological quantum materials since the discovery of the quantum spin Hall effect in 2005. TIs differ from conventional semiconductors and insulators in that they possess unique gapless metallic surface states with an insulating bulk. These surface states are protected from back-scattering and non-magnetic perturbations due to the constraints of time-reversal symmetry (TRS), which makes TIs promising materials for technological applications in spintronics and quantum computing. Besides, many TIs are excellent thermoelectric materials because both share similar material properties such as heavy constituent elements, small bandgaps, and high spin-orbit coupling (SOC) and many TIs are regarded as the best TE materials at room temperature. Searching for high-performance thermoelectric (TE) materials is of crucial importance in order to make use of renewable heat energy efficiently. The efficiency of thermoelectric conversion of TE materials is evaluated by the dimensionless figure of merit (ZT), which is expressed as ZT= S2σT/(κe + κl), where S, σ, T, and κe and κl are Seebeck coefficient, electrical conductivity, absolute temperature, and electronic and lattice thermal conductivities, respectively. In order to attain high TE efficiency, materials with high ZT values are required, which implies that they must have large power factors (PF = S2σ) and low thermal conductivities simultaneously. However, the S and σ are strongly coupled to each other and they correspond oppositely to the carrier density. Therefore, an appropriate charge density cannot be either too large or too small which implies that narrow bandgap materials such as TIs are the most suitable candidates for thermoelectric applications. Thus, in this project, employing first-principles calculations, I will study the topological electronic structures and thermoelectric performance of bulk and 2D materials. This study will help to provide a new playground of materials in which non-trivial topological properties with excellent thermoelectric performance coexist.