Nonsaturating Magnetoresistance and Nontrivial Band Topology of Type‐II Weyl Semimetal NbIrTe₄

Abstract

momentum directions. In the presence of broken time-reversal symmetry (TRS) or space-inversion symmetry, Dirac semimetals evolve into Weyl semimetals and Dirac points split into pairs of Weyl points due to the lifted spin degeneracy. [8,9] For both the Dirac and Weyl semimetals, due to the coexistence of the conventional charge carriers and relativistic carriers, interesting transport phenomena can often be observed, for example, chiral anomaly [10][11][12] and ultrahigh carrier mobilities. [13] Accordingly, transport studies are viewed as an important way to explore the unique scattering mechanism of charge carriers in Dirac/Weyl semimetals. In addition, through transport quantum oscillations, one can get deep insights into the underlying band topology of Dirac/Weyl semimetals.In general, Weyl semimetals can be classified into two types: the standard type I which possesses a point-like Fermi surface, and the type II with strongly tilted Weyl cones induced by the broken Lorentz symmetry. [14] The Weyl points for type II Weyl semimetals appear only at the contact of electron and hole pockets. The qualitatively distinct band topology of type II Weyl semimetals can lead to marked differences in physical properties, such as the direction restricted chiral anomaly and exotic superconductivity. [15][16][17] To date, several noncentrosymmetric material systems, for example, the transition metal dichalcogenides T M X 2 (T M = W, Mo, etc.; X = Se, Te), [14,[18][19][20] the diphosphides (Mo, W)P 2 , [21] LaAlGe, [22] etc., have been considered to be type II Weyl semimetals, while most of them display complex band structures with multiple Weyl points, which adds difficulties in the conventional transport studies of these materials. Moreover, in many Weyl semimetals, the Weyl points are located deeply below the Fermi level, which often hinders the observation of intrinsic characteristics associated with the relativistic carriers.Very recently, ternary MTTe 4 (M = Nb or Ta; T = Ir or Rh) compounds were theoretically predicted as a new series of type II Weyl semimetals, [23,24] and verified experimentally in TaIrTe 4 . [25][26][27] In comparison with the previous type II Weyl semimetals, the angle-resolved photoemission spectroscopy (ARPES) data and band calculation of TaIrTe 4 suggests the existence of only four Weyl points, [24,26] which is the minimum number of Weyl points allowed for a time-reversal invariant Weyl semimetals, characterized by nodal points in the bulk and Fermi arc states on the surface, have recently attracted extensive attention due to their potential application as materials for low-energy-consumption electronics. The thermodynamic and transport properties of a theoretically predicted Weyl semimetal NbIrTe 4 is measured in high magnetic fields up to 35 T and low temperatures down to 0.4 K. Remarkably, NbIrTe 4 exhibits a nonsaturating transverse magnetoresistance that follows a power-law dependence in B. Low-field Hall measurements reveal that hole-like carriers dominate the transport for T > 80 K, while...

Layered van der Waals topological metals of TaTMTe4 (TM = Ir, Rh, Ru) family

“…Among other members of this ternary telluride family NbIrTe 4 was proposed to host type-II Weyl fermions with experimental indica-tions in charge transport measurements [25]. This material also demonstrates non-saturating MR [26]. Recently both binary (WTe 2 , MoTe 2 ) and ternary (TaTMTe 4 , TM=Ir, Rh, Ru) tellurides showed bi-stable resistive metal-insulator switching in point contact measurements at room temperature, bringing those materials closer to applications.…”

Anisotropic transport and quantum oscillations in the quasi-one-dimensional TaNiTe5: Evidence for the nontrivial band topology

“…The quasi-1D topological material candidates reported thus far mainly involve the halogen compounds β-Bi 4 X 4 (X = Br, I) [3][4][5] , α-Bi 4 I 4 5,6 , (TaSe 4 ) 2 I 7-9 , the Weyl semimetal (Ta, Nb)IrTe 4 [10][11][12][13] , and the theoretically proposed molybdenum chalcogenides A 2 Mo 6 X 6 (A = Alkani, In, Tl; X = chalcogen) [14][15][16] , etc. Among them, β-Bi 4 I 4 has been experimentally verified as a weak topological insulator, i.e., the 3D stacking of 2D quantum spin Hall (QSH) states, where topological surface states emerge only on the side surfaces but not on the top and bottom surfaces 5 .…”

Pressure Engineering of the Dirac Fermions in Quasi-One-Dimensional Tl$_2$Mo$_6$Se$_6$

“…The search for new topological states has become the cynosure of condensed matter physics since the discovery of topological insulators [1,2]. With the advent of Dirac and Weyl semimetals (DSMs and WSMs), the research interest in topological phenomena has largely shifted towards various breeds of topological metals or semimetals, including the topological nodal-line semimetals and those with fermionic excitations beyond 4-fold (Dirac) or 2-fold (Weyl) degeneracies [3], e.g., the threefold/sixfold/eightfold degenerate point nodes [4,5]. More recently, a new type of topological fermion has been theoretically proposed, namely the cubically dispersed Dirac semimetal (CDSM) [6,7].…”