Kavli Affiliate: Long Zhang
| First 5 Authors: Zhongdong Han, Tingxin Li, Long Zhang, Rui-Rui Du,
| Summary:
We report a magneto-induced topological phase transition in inverted
InAs/GaSb bilayers from a quantum spin Hall insulator to a normal insulator. We
utilize a dual-gated Corbino device in which the degree of band inversion, or
equivalently the electron and hole densities, can be continuously tuned. We
observe a topological phase transition around the magnetic field where a band
crossing occurs, that is accompanied by a bulk-gap closure characterized by a
bulk conductance peak (BCP). In another set of experiments, we study the
transition under a tilted magnetic field (tilt angle $theta$). We observe the
characteristic magneto-conductance around BCP as a function of $theta$, which
dramatically depends on the density of the bilayers. In a relatively
deep-inversion (hence a higher density) regime, where the electron-hole
hybridization dominates the excitonic interaction, the BCP grows with $theta$.
On the contrary, in a shallowly-inverted (a lower density) regime, where the
excitonic interaction dominates the hybridization, the BCP is suppressed
indicating a smooth crossover without a gap closure. This suggests the
existence of a low-density, correlated insulator with spontaneous symmetry
breaking near the critical point. Our highly controllable electron-hole system
offers an ideal platform to study interacting topological states as proposed by
recent theories.
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