Is the insulating state of monolayer WTe_2 an excitonic insulator? · revision history

Revision 2

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Title · changed
Revision 1: Is the insulating state of monolayer WTe2 an excitonic insulator
Revision 2: Is the insulating state of monolayer $\mathrm{WTe_2}$ an excitonic insulator?
Plain · changed
Revision 1: Monolayer WTe2 is insulating at charge neutrality and conducts along its edges. Experiments suggest the bulk gap comes from electron-hole pairing, but a gap from ordinary band mixing or disorder has not been ruled out.
Revision 2: Monolayer $\mathrm{WTe_2}$ is insulating at charge neutrality and conducts along its edges. Experiments suggest the bulk gap comes from electron-hole pairing, but a gap from ordinary band mixing or disorder has not been ruled out.
Precise
Monolayer 1T'-WTe2 has a small bulk gap at charge neutrality that closes with gate-induced doping; 2022 experiments interpreted it as an interaction-driven excitonic insulator, possibly with spontaneous symmetry breaking. Determine whether the gap is an excitonic condensate (order parameter, symmetry breaking, mean-field or BKT-like temperature dependence, collective mode) or a single-particle hybridization gap enhanced by interactions. An answer is the identified gap origin with evidence for or against a broken symmetry.
Settled by
Direct detection of the predicted broken symmetry (e.g. by optical second-harmonic generation or scanning tunneling spectroscopy of order-parameter domains) or of an excitonic collective mode.
Kind
phenomenon
Answer type
identification
References
(empty)
Literature status
contested
Status note
2022 Nature Physics reports gave excitonic signatures; independent evidence of a broken symmetry had not appeared as of 2025.
Posed since
(empty)

Decisions