@article{WOS:000613942700067,
 abstract = {Topological insulators, along with Chern insulators and quantum Hall
insulator phases, are considered as paradigms for symmetry protected
topological phases of matter. This article reports the experimental
realization of the time-reversal invariant helical edge-modes in bilayer
graphene/monolayer WSe2-based heterostructures-a phase generally
considered as a precursor to the field of generic topological
insulators. Our observation of this elusive phase depended crucially on
our ability to create mesoscopic devices comprising both a moire
superlattice potential and strong spin-orbit coupling; this resulted in
materials whose electronic band structure could be tuned from trivial to
topological by an external displacement field. We find that the
topological phase is characterized by a bulk bandgap and by helical
edge-modes with electrical conductance quantized exactly to 2e(2)/h in
zero external magnetic field. We put the helical edge-modes on firm
ground through supporting experiments, including the verification of
predictions of the Landauer-Buttiker model for quantum transport in
multiterminal mesoscopic devices. Our nonlocal transport properties
measurements show that the helical edge-modes are dissipationless and
equilibrate at the contact probes. We achieved the tunability of the
different topological phases with electric and magnetic fields, which
allowed us to achieve topological phase transitions between trivial and
multiple, distinct topological phases. We also present results of a
theoretical study of a realistic model which, in addition to replicating
our experimental results, explains the origin of the topological
insulating bulk and helical edge-modes. Our experimental and theoretical
results establish a viable route to realizing the time-reversal
invariant Z(2) topological phase of matter.},
 author = {Tiwari, Priya and Srivastav, Saurabh Kumar and Ray, Sujay and Das,
Tanmoy and Bid, Aveek},
 doi = {10.1021/acsnano.0c07524},
 eissn = {1936-086X},
 issn = {1936-0851},
 journal = {ACS NANO},
 month = {JAN 26},
 number = {1},
 orcid-numbers = {SRIVASTAV, SAURABH/0000-0002-0498-4217
Bid, Aveek/0000-0002-2378-7980},
 pages = {916-922},
 researcherid-numbers = {Bid, Aveek/F-3076-2010},
 title = {Observation of Time-Reversal Invariant Helical Edge-Modes in Bilayer
Graphene/WSe2 Heterostructure},
 unique-id = {WOS:000613942700067},
 volume = {15},
 year = {2021}
}