Thermoelectric transport properties of borophane

Abstract

We theoretically study the influence of impurity scattering on the electric and thermal transport of borophane layer, a two-dimensional anisotropic Dirac semi-metal with two tilted and anisotropic Dirac cones. In a systematic framework, we have calculated exactly the electrical conductivity and thermoelectric coefficients of borophane in the presence of the short-range, long-range charged impurity and the short-range electro-magnetic (SREM) scatterers, by using the exact solution of the Boltzmann transport equation within the linear-response theory. Contrary to the large electron-hole asymmetry in borophane, its electron-hole conductivity is nearly symmetric. Interestingly, for the short-range scatters, just like graphene, the short-range conductivities of borophane have the constant values, independent of the chemical potential, while the conductivities of the SREM scatterers are linearly dependent on the chemical potential. Regardless of the impurity type, the electric conductivity of borophane is highly anisotropic, while the Seebeck coefficient and figure of merit (ZT ) are isotropic. Along with the ambipolar nature of the borophane thermopower, a very high value of ZT around unity is obtained at room temperature, due to the large asymmetry between electrons and holes in borophane. More importantly, borophane attains its maximum value of ZT at very low chemical potentials, in the vicinity of the charge neutrality point. In comparison to phosphorene, a highly unique anisotropic 2D material, borophane with a higher anisotropy ratio (σxx/σyy ∼ 10), is an unprecedented anisotropic material. This high anisotropy ratio together with the large figure of merit, suggest that borophane is promising for the thermoelectric applications and transport switching in the Dirac transport channels. arXiv:1811.09915v2 [cond-mat.mes-hall]

Determining the Electronic Structure and Thermoelectric Properties of MoS2/MoSe2 Type‐I Heterojunction by DFT and the Landauer Approach

“…From our calculations of the Seebeck coefficient, in all heterojunctions the crossover from hole‐controlled to electron‐controlled conduction, i.e., going from positive to negative values, takes place before μ − E F = 0 ( Figure ), indicating that electron‐controlled conduction dominates. [ 38 ] Seebeck coefficient is symmetric around the crossover point in MoS 2 /MoSe 2 heterojunction configurations; however, the MoSe 2 /MoS 2 configurations are slightly asymmetrical just around the crossover point.…”

Valley-polarized and supercollimated electronic transport in an 8-Pmmn borophene superlattice

“…•r dx, where r = (x, y). If we choose the parameters of the potential as d A = d B = 10 nm, V A = 50 meV, V B = 0, N = 10, the momentum difference between the two Dirac cones is given as [16,20], the intervalley scattering matrix element can be estimated, and is very small as in the order of 10 −4 . On the other hand, the periodic potential is assumed to vary slowly on the atomic scale.…”

“…The first-principles calculations and effective low-energy model show that it also hosts massless Dirac fermions, and more interestingly, its Dirac cones are tilted and anisotropic [14][15][16], different from the isotropic Dirac cones in graphene. Based on these unique characteristics, a series of intriguing physical phenomena has been confirmed, such as oblique Klein tunneling [17,18], anisotropic plasmons [19], excellent thermoelectric performance [20], anomalous Andreev reflection [21], and so on.…”

Tuning the electronic structure and magnetic coupling in armchair B2S nanoribbons using strain and staggered sublattice potential

“…We have recently addressed the problem of isolated magnetic adatoms placed on silicene [39] and phosphorene [40] sheets as well as on zigzag silicene nanoribbons [16] and bilayer phosphorene nanoribbons [41]. In a detailed study, we found that the RKKY interaction in silicene can be written in an anisotropic Heisenberg form for the intrinsic case where the spin coupling could realize various spin models, e.g., the XXZ-like spin model [39]. In another work, it has concluded that the RKKY interaction in the bulk phosphorene monolayer is highly anisotropic and the magnetic ground-state of two magnetic adatoms can be tuned by changing the spatial configuration of impurities as well as the chemical potential varying [40].…”

“…We have recently addressed the problem of isolated magnetic adatoms placed on silicene [39] and phosphorene [40] sheets as well as on zigzag silicene nanoribbons [16] and bilayer phosphorene nanoribbons [41]. In a detailed study, we found that the RKKY interaction in silicene can be written in an anisotropic Heisenberg form for the intrinsic case where the spin coupling could realize various spin models, e.g., the XXZ-like spin model [39].…”