Observation of gapless Dirac surface states in ZrGeTe

Abstract

The experimental discovery of the topological Dirac semimetal establishes a platform to search for various exotic quantum phases in real materials. ZrSiS-type materials have recently emerged as topological nodal-line semimetals where gapped Dirac-like surface states are observed. Here, we present a systematic angle-resolved photoemission spectroscopy (ARPES) study of ZrGeTe, a nonsymmorphic symmetry protected Dirac semimetal. We observe two Dirac-like gapless surface states at the sameX point of the Brillouin zone. Our theoretical analysis and first-principles calculations reveal that these are protected by crystalline symmetry. Hence, ZrGeTe appears as a rare example of a naturally fine tuned system where the interplay between symmorphic and non-symmorphic symmetry leads to rich phenomenology, and thus opens for opportunities to investigate the physics of Dirac semimetallic and topological insulating phases realized in a single material. arXiv:1711.08011v1 [cond-mat.mes-hall] 21 Nov 2017 the X (R) point. Here ↑(↓) denotes a pseudospin in the presence of SOC corresponding to the P Θ eigenvalue +i(−i). (b),(c) Our ab initio calculations yield two band inversions at R (and the equivalent TRIM) in bulk ZrGeTe. The calculated products of parity eigenvalues at the nonequivalent TRIMs are shown in the tables. As we write below each table, each band inversion corresponds to a different eigenvalue of the Mẑ nonsymmorphic symmetry operator, as discussed in the sections below. (d) Bottom: Schematics of the first octant of the BZ and non-equivalent high-symmetry points (TRIMs). In parenthesis the parity of δ(Γ i ) is shown. Top: Brillouin zone of the (110) surface that is probed by our ARPES measurements. The bulk inversions induce two Dirac surface states at theX 1 andX 2 , respectively, which we observed by ARPES. For each surface

Evidence for bulk nodal loops and universality of Dirac-node arc surface states in ZrGeXc ( Xc=S , Se, Te)

“…In fact, previous VUV-ARPES measurements on this material class (e.g. ZrSiS and HfSiS) [32][33][34][35][36][37][38][39][40] significantly suffered from the strong k z -broadening effect and, as a result, could not precisely argue the 3D dispersion of the bulk bands. Figure 1(c) shows the ARPES-intensity mapping at E F as a function of k z and in-plane wave vector k along the ΓM cut obtained with SX photons.…”

“…1(b)] protected by screw and time-reversal symmetries, and another with a diamond shape around E F at k z = 0 and π planes protected by glide mirror symmetry. Besides these bulk states, a SS has been commonly observed around theX point in ZrSiX c (X c = S, Se, Te), HfSiS, ZrSnTe, and ZrGeTe [32][33][34][35][36][37][38][39][40]. This SS is located away from the nodal loops and may originate from a dangling bond or a "floating" SS [39] created by a symmetry reduction at the surface, as shown in first-principles band-structure calculations [41].…”

Tunable large spin Hall and spin Nernst effects in the Dirac semimetals ZrXY (X=Si,Ge;Y=S,Se,Te)Yen1, Guo2 2020Phys. Rev. B392260View full textAdd to dashboardCite

“…For example, the recent studies on the SHE in the rutile oxide Dirac semimetals [26] and the TaAs Weyl semimetal family [27] showed that the anticrossing of the nodal points and nodal lines in these TSMs could be the sources of Among the Dirac semimetals, the studies of the ZrSiStype compounds have been particularly intense in the past few years. The members of the ZrSiS family share the same space group P 4/nmm (No.129), and they all possess the symmetry protected Dirac nodal features in the band structures [23,[28][29][30]. In addition, several exotic quantum phenomena such as highly anisotropic magnetoresistance [31], gapless Dirac surface states in topological crystalline insulator (TCI) phase [29], Shubnikovde Haas and de Haas-van Alphen oscillations [30,32], have been observed in some compounds of the family.…”

“…The members of the ZrSiS family share the same space group P 4/nmm (No.129), and they all possess the symmetry protected Dirac nodal features in the band structures [23,[28][29][30]. In addition, several exotic quantum phenomena such as highly anisotropic magnetoresistance [31], gapless Dirac surface states in topological crystalline insulator (TCI) phase [29], Shubnikovde Haas and de Haas-van Alphen oscillations [30,32], have been observed in some compounds of the family. Nonetheless, the spin Hall effect and spin Nernst effect in such systems have not been studied yet.…”

Disentangling orbital and spin textures of surface-derived states in non-symmorphic semimetal HfSiS

“…Recently the non-symmorphic Dirac nodal-line semimetals WHM (W = Zr, Hf, La; H = Si, Ge, Sn, and Sb; M = S, Se, Te, O) [21][22][23][24][25][26][27][28][29] have been theoretically and experimentally investigated. HfSiS is the most representative compound because of the emergence of spin-split surface states (SSs) due to strong SOC at theX point with C 2v symmetry near the Fermi level [22,24].…”