350 research outputs found
Manipulation of Topological States and Bulk Band Gap Using Natural Heterostructures of a Topological Insulator
We have performed angle-resolved photoemission spectroscopy on
(PbSe)5(Bi2Se3)3m, which forms a natural multilayer heterostructure consisting
of a topological insulator (TI) and an ordinary insulator. For m = 2, we
observed a gapped Dirac-cone state within the bulk-band gap, suggesting that
the topological interface states are effectively encapsulated by block layers;
furthermore, it was found that the quantum confinement effect of the band
dispersions of Bi2Se3 layers enhances the effective bulk-band gap to 0.5 eV,
the largest ever observed in TIs. In addition, we found that the system is no
longer in the topological phase at m = 1, pointing to a topological phase
transition between m = 1 and 2. These results demonstrate that utilization of
naturally-occurring heterostructures is a new promising strategy for realizing
exotic quantum phenomena and device applications of TIs.Comment: 5 pages, 5 figure
Unexpected Dirac-Node Arc in the Topological Line-Node Semimetal HfSiS
We have performed angle-resolved photoemission spectroscopy on HfSiS, which
has been predicted to be a topological line-node semimetal with square Si
lattice. We found a quasi-two-dimensional Fermi surface hosting bulk nodal
lines, alongside the surface states at the Brillouin-zone corner exhibiting a
sizable Rashba splitting and band-mass renormalization due to many-body
interactions. Most notably, we discovered an unexpected Dirac-like dispersion
extending one-dimensionally in k space - the Dirac-node arc - near the bulk
node at the zone diagonal. These novel Dirac states reside on the surface and
could be related to hybridizations of bulk states, but currently we have no
explanation for its origin. This discovery poses an intriguing challenge to the
theoretical understanding of topological line-node semimetals.Comment: 5 pages, 4 figures (paper proper) + 2 pages, figures (supplemental
material
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