Switching of band inversion and topological surface states by charge density wave

Abstract

Topologically nontrivial materials host protected edge states associated with the bulk band inversion through the bulk-edge correspondence. Manipulating such edge states is highly desired for developing new functions and devices practically using their dissipation-less nature and spin-momentum locking. Here we introduce a transition-metal dichalcogenide VTe2, that hosts a charge density wave (CDW) coupled with the band inversion involving V3d and Te5p orbitals. Spin- and angle-resolved photoemission spectroscopy with first-principles calculations reveal the huge anisotropic modification of the bulk electronic structure by the CDW formation, accompanying the selective disappearance of Dirac-type spin-polarized topological surface states that exist in the normal state. Thorough three dimensional investigation of bulk states indicates that the corresponding band inversion at the Brillouin zone boundary dissolves upon the CDW formation, by transforming into anomalous flat bands. Our finding provides a new insight to the topological manipulation of matters by utilizing CDWs’ flexible characters to external stimuli.

Axionic band topology in inversion-symmetric Weyl-charge-density waves

“…Our methodology can be extended to spin-density waves [69,[114][115][116] and CDWs in T -symmetric semimetals, including Dirac [97,117,118], Weyl, and nodal-line semimetals [119][120][121][122], which also exhibit signatures of higher-order topology [55,100,123,124]. Most interestingly, because rotation-and T -symmetric HOTIs [28,56] can be formed from weak stacks of 2D TIs [48,51], rotationsymmetric CDWs in T -symmetric WSMs, such as the CDW in (TaSe 4 ) 2 I [78], may also exhibit nontrivial response effects.…”

Electronic states of multilayer VTe2: quasi-one-dimensional Fermi surface and implications to charge-density waves

“…These results do not support the FS-nesting-driven structural transition. Thus, the mechanism of structural transition in ultrathin VTe 2 would be different from that of bulk showing the 1T "-to-1T phase transition at 482 K, because the bulk 1T " phase can be associated with the formation of CDW 27 .…”

“…[20][21][22][23][24] VTe 2 is an excellent target to address the essential question regarding the evolution of physical properties upon the 2D-3D crossover, because the electronic property shows an intriguing difference between monolayer and bulk. Bulk VTe 2 forms the monoclinic 1T " phase with 3×1×3 PLD and undergoes a structural transition to the polymorphic 1T structure at T = 482 K [25][26][27] . On the other hand, monolayer VTe 2 stabilizes with the 1T structure [28][29][30][31][32][33] and exhibits the 4×4 CDW [25][26][27] .…”

“…Bulk VTe 2 forms the monoclinic 1T " phase with 3×1×3 PLD and undergoes a structural transition to the polymorphic 1T structure at T = 482 K [25][26][27] . On the other hand, monolayer VTe 2 stabilizes with the 1T structure [28][29][30][31][32][33] and exhibits the 4×4 CDW [25][26][27] . Although the relationship between fermiology and PLD as well as the origin of different crystal structures between monolayer and bulk have been intensively discussed, these key questions 34,35 are still controversial [34][35][36][37] .…”

Topological charge density wave in monolayer NbSe2

“…A new frontier in condensed matter physics concerns the study of emergent topological phases in correlated materials [1,2]. Recent proposals, which have focused on realizing a topological charge ordered (TCO) state in materials [3][4][5][6] start by assuming a pre-existing topological order before introducing the charge density wave (CDW) transition. It remains unclear how a topological state could emerge driven by the spontaneous symmetry breaking (SSB) involved in the formation of the CDW itself.…”