Electron–phonon interaction and transport properties of metallic bulk and monolayer transition metal dichalcogenide TaS ₂

Abstract

Transition metal dichalcogenides have recently emerged as promising two-dimensional materials with intriguing electronic properties. Existing calculations of intrinsic phonon-limited electronic transport so far have concentrated on the semicondcucting members of this family. In this paper we extend these studies by investigating the influence of electron-phonon coupling on the electronic transport properties and band renormalization of prototype inherent metallic bulk and monolayer TaS2. Based on density functional perturbation theory and semi-classical Boltzmann transport calculations, promising room temperature mobilities and sheet conductances are found, which can compete with other established 2D materials, leaving TaS2 as promising material candidate for transparent conductors or as atomically thin interconnects. Throughout the paper, the electronic and transport properties of TaS2 are compared to those of its isoelectronic counterpart TaSe2 and additional informations to the latter are given. We furthermore comment on the conventional superconductivity in TaS2, where no phonon-mediated enhancement of TC in the monolayer compared to the bulk state was found. A. IntroductionSucceeding the many advances in fundamental science and applications of graphene, other two-dimensional materials, especially the transition-metal dichalcogenides (TMDs), have attracted remarkable interest for their appealing electrical, optical and mechanical properties. TMDs form layered compounds having a metal layer sandwiched between two chalcogen layers. These monolayers are weakly bound to each other by the dispersive van der Waals interaction, leading to a quasi-twodimensional behavior in the monolayers 1,2 . Among the TMDs, exfoliated semi-conducting materials, e.g. MoS 2 and WS 2 , have been extensively in focus for their promising electronic mobilities and thus a high potential in thin-film transistor applications [3][4][5] . Recently metallic TMDs are in focus for their potential as transparent conductive electrodes and gained increasing importance for information-, optoelectronic-and energy-applications 6,7 . Crucial requirements for these are high electrical conductivity and high transparency; properties that are often contradicting.Based on density functional theory and semi-classical Boltzmann transport, we will elaborate and discuss the influence of electron-phonon coupling onto the electronic transport properties and band renormalization of prototype metallic bulk and monolayer TaS 2 and compare it to conventionally used two-dimensional and bulk materials. Additional details on to the isoelectronic counterpart monolayer TaSe 2 are given along the discussion and can be found in the supplemental material 8 . Furthermore the influence of low-dimensionality on the phononmediated superconductivity in metallic TaS 2 will be discussed. While the Mermin-Wagner theorem 9-11 suggests that in two-dimensional systems no superconductivity, or even an enhancement compared to its bulk state, should be observed, opposite trends have bee...

Gapped metals as thermoelectric materials revealed by high-throughput screening

“…Moreover, calculated band structure using HSE confirms the presence of the two band gaps for TaS 2 [48]. Electron-phonon scattering in TaS 2 was recently studied theoretically [76], but no Seebeck coefficient was reported. In general the effect of the doping on the Seebeck coefficient seems not to have been investigated extensively in this class of metallic compounds.…”

“…In the literature, the existence of one or two band gaps in these materials was recently considered for optical applications in Ref. [76]. A low Seebeck coefficient was reported in Ref.…”

Electron–phonon coupling in single-layer MoS2

“…The electron-phonon induced broadening of the electronic states was obtained within a modified version of the EPW code [29]. An improved tetrahedron Fermi-surface-adaptive integration scheme based on the Wannier-interpolated electron-phonon matrix elements was applied [30][31][32]. Wannier interpolated electronic bands had an error of less than 5 meV compared to the ab initio derived eigenvalues.…”

Electron-phonon coupling and the coexistence of superconductivity and charge-density wave in monolayer NbSe2

“…Except this, there is no significant changes. In fact, a similar method was used to investigate the influence of electron-phonon coupling on electronic transport properties [33].…”