Crystalline topological Dirac semimetal phase in rutile structure β′−PtO2

Abstract

Based on first-principles calculations and symmetry analysis, we propose that a transition metal rutile oxide, in particular β -PtO2, can host a three-dimensional topological Dirac semimetal phase. We find that β -PtO2 possesses an inner nodal chain structure when spin-orbit coupling is neglected. Incorporating spin-orbit coupling gaps the nodal chain, while preserving a single pair of threedimensional Dirac points protected by a screw rotation symmetry. These Dirac points are created by a band inversion of two d bands, which is a realization of a Dirac semimetal phase in a correlated electron system. Moreover, a mirror plane in the momentum space carries a nontrivial mirror Chern number nM = −2, which distinguishes β -PtO2 from the Dirac semimetals known so far, such as Na3Bi and Cd3As2. If we apply a perturbation that breaks the rotation symmetry and preserves the mirror symmetry, the Dirac points are gapped and the system becomes a topological crystalline insulator.arXiv:1809.08963v2 [cond-mat.str-el]

Strong and fragile topological Dirac semimetals with higher-order Fermi arcs

“…We predict previously unidentified HOFAs and related fragilephase corner charges (Supplementary Note 9) in established candidate Dirac semimetals. We present ab initio and tightbinding calculations demonstrating the presence of HOFAs in the intermediate-temperature (α″) phase of the well-studied Dirac semimetal Cd 3 As 2 in space group (SG) 137 (P4 2 =nmc1 0 ) 10,18,56,57 and in the candidate Dirac semimetals KMgBi in SG 129 (P4=nmm1 0 ) 58,59 and rutile-structure (β 0 -) PtO 2 in SG 136 (P4 2 =mnm1 0 ) 60,61 (here and throughout this work, we follow ref. 62 in using primes to denote antiunitary group elements).…”

“…This is analogous to the helical hinge modes in the HOTI bismuth, which are only observable in samples that are cut into nanowires (or terminated with step edge configurations) that preserve bulk rotation and I symmetries 31 . A number of candidate Dirac semimetals have already been identified in the SGs in Table 2, including the aforementioned α and α″ phases of Cd 3 As 2 , the rutile-structure (β 0 -) phase of PtO 2 in SG 136 (P4 2 =mnm1 0 ) 60,61 , and families of tilted Dirac semimetals related to VAl 3 in SG 139 (I4=mmm1 0 ) 70 , YPd 2 Sn in SG 225 (Fm 3m1 0 ) 71 , and KMgBi in SG 129 (P4=nmm1 0 ) 58,59 .…”

“…5, we also examine the bulk and hinge spectra of the candidate Dirac semimetal β′-PtO 2 . Single crystals of PtO 2 in its rutile-structure (β 0 ) phase have previously been prepared in experiment 60 , and its bulk and surface electronic structure were examined in a previous theoretical work 61 . In β′-PtO 2 , the Hamiltonian of the k z = 0 plane is equivalent to a 2D TCI with mirror Chern number C M z ¼ 2; therefore β′-PtO 2 is more closely related to the s-d-hybridized HOFA semimetal model introduced in this work (Eq.…”

Topological semimetallic phase in PbO2 promoted by temperature

“…Technically, spin-orbit coupling breaks the SU(2) symmetry, generally gapping the nodal line with only one pair of Dirac points along the Γ-Z line remaining, as has been previously observed [36]. The Dirac points are protected by the fourfold screw rotationC 4z symmetry, which is a fourfold rotation about the z axis, followed by a translation by (a/2,a/2,c/2) [47]. Thus the nodal-line semimetal evolves into a Dirac semimetal with the inclusion of spinorbit coupling.…”

“…In the absence of spin-orbit coupling, for each mirror plane the inverted band states have mirror eigenvalues −1 and +1 respectively, thus the two crossing bands cannot hybridize with each other and are therefore not gapped, forming a nodal line on the plane. The two nodal lines on the (110) and (110) planes are identical, which is similar to transitionmetal rutile oxide PtO 2 [47]. For comparison, the band crossing on the Γ-X high-symmetry line is not protected by mirror symmetry and therefore gapped.…”