Large nonsaturating magnetoresistance and pressure-induced phase transition in the layered semimetal HfTe2

Abstract

Unusual physical properties like large magnetoresistance (MR) and superconductivity occurring in semimetals with Dirac or Weyl points are often linked to their topologically nontrivial band structures. However, there is an increasing number of reports on semimetals that show large MR in the absence of Dirac or Weyl points. Herein we report an experimental and theoretical study on the layered transition-metal dichalcogenide (TMDC) HfTe 2 that shows a large MR of 1350% at T = 2 K and μ 0 H = 9 T in the absence of Dirac or Weyl points. Moreover, the structure and electrical resistivity under pressure reveal a unique structural transition. These results clearly distinguish HfTe 2 from TMDCs like MoTe 2 or WTe 2 which both exhibit larger MR and are viewed as Weyl semimetals. HfTe 2 is an appealing platform for future investigations on the interplay of particular band-structure features and their connection to emerging physical properties.

Bulk and surface electronic states in the dosed semimetallic HfTe2

“…The modified Becke-Johnson (mBJ) functional [25] was used (see text for discussion). The used lattice parameters are a = b = 3.911 Å, c = 6.649 Å, and z Te = 0.266 [20], and the R MT K max parameter was equal to 7.0.…”

“…A recent ARPES study of thin films of HfTe 2 claimed that 1T-HfTe 2 might be classed as a topological Dirac semimetal [19], though the bands observed in measurements of single crystals did not support this [10]. Still, 1T-HfTe 2 shows a notably large and nonsaturating magnetoresistance, resulting from the carrier compensation [20]. Its electronic structure is closely analagous to that of TiSe 2 , which exhibits a CDW and can host superconductivity upon electron doping, though no such phase transition have been detected in HfTe 2 to date [15,17,20].…”

“…Still, 1T-HfTe 2 shows a notably large and nonsaturating magnetoresistance, resulting from the carrier compensation [20]. Its electronic structure is closely analagous to that of TiSe 2 , which exhibits a CDW and can host superconductivity upon electron doping, though no such phase transition have been detected in HfTe 2 to date [15,17,20].…”

“…1T-HfTe 2 is a transition-metal dichalcogenide (TMD) which has a semimetallic electronic structure, with both electronlike and holelike bands crossing the Fermi level [10,[14][15][16][17][18][19][20]. Early studies of this material were focused on the fundamental properties such as the stoichiometry, lattice constants, transport properties and thermopower [14,15,17,18,21,22].…”

Phase engineering of two-dimensional transition metal dichalcogenides

“…Besides, the transformation from 2H-MoSe 2 to 1T-LiMoSe 2 can also be realized [70]. It is noteworthy that Li-intercalation is generally driven by external assistance, such as ball milling [78], electrochemical process [79,80], and sonication [81,82], which can help to TiS 2 1T Metallicity [35] TiSe 2 1T Metallicity [36] TiTe 2 1T Metallicity [37] ZrS 2 1T Semiconducting (1.4 eV) [38] ZrSe 2 1T Semiconducting (0.95 eV) [39] ZrTe 2 1T Dirac semimetallicity [40] HfS 2 1T Semiconducting (1.45 eV) [41] HfSe 2 1T Semiconducting (1.13 eV) [39] HfTe 2 1T Semimetallicity [42] VS 2 1T Semiconducting (0.3 eV, 2-3 layers) [43] Metallicity (>8 layers) [44] VSe 2 1T Metallicity [18] VTe 2 1T Metallicity [45] NbS 2 2H Metallicity [46] 1T Metallicity [47] NbSe 2 2H Metallicity [16] 1T Metallicity [48] NbTe 2 1T Metallicity [45] TaS 2 2H Metallicity [49] 1T Metallicity [50] TaSe 2 2H Metallicity [51] 1T Metallicity [52] TaTe 2 1T' Metallicity [45] MoS 2 2H Semiconducting (1.85 eV) [53] 1T Metallicity [54] MoSe 2 2H Semiconducting (1.55 eV) [55] 1T Metallicity [56] MoTe 2 2H Semiconducting (1.1 eV) [57] 1T' Metallicity [58] T d Weyl semimetallicity [59] WS 2 2H Semiconducting (2.02 eV) [60] 1T Metallicity [25] WSe 2 2H Semiconducting (1.7 eV) [61...…”