Kavli Affiliate: Jie Shan
| First 5 Authors: Phuong X. Nguyen, Raghav Chaturvedi, Bo Zou, Kenji Watanabe, Takashi Taniguchi
| Summary:
Quantum oscillations in magnetization or resistivity are a defining feature
of metals subject to an external magnetic field. The phenomenon is generally
not expected in insulators without a Fermi surface. The observations of quantum
oscillations in Kondo insulating materials have provided a rare counterexample
and attracted much theoretical interest. However, the magnetic oscillations in
correlated insulators remain poorly understood. Here we report the observations
of resistivity quantum oscillations in an excitonic insulator realized in
Coulomb-coupled electron-hole double layers with gate-tunability that allows
the phenomenon to be explored in a more controllable fashion than in bulk
materials. When the cyclotron energy of the electrons or holes is tuned to be
comparable to or larger than the exciton binding energy, recurring transitions
between excitonic insulators and electron-hole decoupled quantum Hall states
are observed. Compressibility measurements show an oscillatory exciton binding
energy as a function of magnetic field and electron-hole pair density. Coulomb
drag measurements further reveal the formation of excitons with finite angular
momentum. Our results are qualitatively captured by mean-field theory
calculations. The study demonstrates a new platform for studying quantum
oscillations in correlated insulators.
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