Strong correlations and orbital texture in single-layer 1T-TaSe2

Deconfinement of Mott localized electrons into topological and spin–orbit-coupled Dirac fermions

“…This is similar to the configuration observed experimentally in ref. 15 and it is thus plausible that also the honeycomb configuration considered here, is within reach of experiments. Experimental approaches including tear-and-stack 22 and Scanning Tunneling Microscopy voltage pulse-based manipulation schemes 23 can present possible avenues to control and switch metastable stacking configurations and to reach the honeycomb configurations discussed in our paper.…”

“…1c). While this kind of local stacking is not the most commonly observed one of the T-phase TMDCs 15,17 , a corresponding stacking sequence has been found in transmission electron microscopy studies of 1T-TaS 2 17 and turns out to be metastable in density functional theory (DFT) simulations of 1T-TaSe 2 21 . Regarding the stacking of the SoD centers further van der Waals DFT total energy calculations (see Supplementary Information) show that the particular honeycomb arrangement studied here, is metastable and energetically on the order of 10 meV per formula unit above the lowest energy configuration.…”

“…In 1T-TaSe 2 , the bulk remains conductive till lowest temperatures, while the surface exhibits a Mott transition around 250 K 11,12 . Recently, 1T-TaSe 2 has been fabricated down to monolayer thickness [13][14][15] and a pronounced thickness dependence of the electronic structure has been reported 15 . As bonds between the layers are mainly of van der Waals type, different stacking configurations are observed in experiments 16,17 and have a strong impact on the electronic structure [18][19][20] .…”

“…The effective Hubbard interaction U for the SoD Wannier orbitals of CCDW TaSe 2 calculated in RPA is U ≈ 130 meV, which is also in line with the experimental estimates in ref. 15 and calculations for TaS 2 19 . The ratio of hopping to Coulomb interaction is decisive in determining the strength and kind of electronic correlation phenomena taking place.…”

Impurity-induced resonant spinon zero modes in Dirac quantum spin liquids

“…The unique properties of quantum spin liquids have attracted much research interest [6][7][8], in particular for their emergent Majorana physics [9] and their long-standing relation with unconventional superconductivity [10,11]. A variety of compounds showing quantum spin-liquids physics have been identified [12][13][14][15][16][17][18][19][20][21][22], including the gapless triangular lattice Dirac quantum spin-liquid in NaYbO 2 [23,24] and different van der Waals materials [25][26][27][28]. Interestingly, finding gapless Dirac spin liquids in van der Waals materials would provide a spinon version of graphene Dirac electrons, opening the door to explore strain gauge fields in spinons [29][30][31], spinon flat bands by twist engineering [32][33][34][35], and impurityinduced spinon resonances [36,37].…”