High thermoelectric efficiency of LaX (X  =  Sb, Bi) two dimensional topological insulators

Abstract

Topological insulators with novel surfaces or edge states are the topological nature sequel of bulk electronic wave functions of these materials. The observed signatures in the electronic structure of topological insulators can make them excellent candidates for thermoelectric materials. Low dimensional materials such as phosphorene and Bi 2 Te 3 nanowire have been confirmed to be desirable for the design of devices with high thermoelectric performance. So in this work, the phonon modes, formation energy and cohesive energy of LaX (X = Sb, Bi) monolayers are first calculated and investigated. Then the band order of these monolayers is investigated by the band structure calculations and the topological phase of these monolayers is proved by using the calculation of Z 2 topological invariant. The energy band gap and the band inversion strength of these monolayers are evaluated under in-plane strains. Also, the effect of different temperatures and in-plane strains on the thermoelectric performance of LaX monolayers is studied. The results show the high thermoelectric efficiency and d-p topological band inversion of these monolayers under compressive strains.

New insights into band inversion and topological phase of TiNI monolayer

“…Therefore, the two Bravais primitive lattice vectors can be expressed as shown in eqn (6), and the reciprocal lattice basis vectors can be calculated immediately, as given in eqn (7).…”

“…[1][2][3][4][5][6] The quantum spin Hall (QSH) insulators, known as 2D TIs, host an insulating bulk gap and unique edge states that are protected by timereversal symmetry (TRS). 3,[7][8][9] In addition to 2D TIs, another class of 2D quantum materials is 2D topological Dirac semimetals. Graphene is the first and most obvious example of 2D Dirac materials.…”

Computational prediction of thermoelectric properties of 2D materials

“…Recent studies on different AB type materials such as XO (X = Sn, Pb, Cu, Ni) [53-56] [22-25], GaX (X = S, Se, Te) [57][58][59][60][61], β -BiX (X = As, Sb) [62], InX (X = S, Se, Te) [59,61,63,64], XP (X = Si, Ge) [65], InX (X = N, P, As, Sb, Bi) [66,67], PbX (X = S, Se, Te) [68][69][70][71], allotropes of SnSe monolayer [72], XSe (X = Si, Ge, Sn) [73], XN (X = B, Al, Ga, Tl) [74,75], ZnX (X = O, S, Se) [76][77][78][79][80], BX (X = P, As, Sb) [81] and LaX (X = Sb, Bi) [82] etc have been reported. This class of materials have achieved higher values of figure of merit (ZT) and are supposed to be promising thermoelectric materials.…”

Topological phase and thermoelectric properties of bialkali bismuthide compounds (Na, K)2RbBi from first-principles

“…Also, the power factor (PF) is defined as PF = S 2 σ. High-efficiency TE materials usually require a large Seebeck coefficient or high PF, high electrical conductivity, and low thermal conductivity. These parameters are usually counter-indicative and change with the carrier concentration [1,2]. For example, the large Seebeck coefficient usually happens at low carrier concentration, leading to low electrical conductivity.…”