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Collective interlayer pairing and pair superfluidity in vertically stacked layers of dipolar excitons
Michal Zimmerman1, Ronen Rapaport1, Snir Gazit1,2
1The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel.
Summary
We theoretically investigate interlayer pairing in stacked indirect exciton (IX) layers. Our findings reveal unique energy shifts and Berezinskii-Kosterlitz-Thouless (BKT) transitions, guiding future experimental observations of pair superfluidity.
Area of Science:
- Condensed Matter Physics
- Quantum Fluids
- Exciton Physics
Background:
- Layered bosonic dipolar fluids may host interlayer molecular bound states, but experimental evidence is lacking.
- Recent experiments in stacked quantum wells motivate theoretical study of interlayer pairing.
Purpose of the Study:
- To theoretically investigate experimental signatures of collective interlayer pairing in vertically stacked indirect exciton (IX) layers.
- To identify observable phenomena that distinguish interlayer pairing from independent condensation.
- To propose experimental conditions for observing pair superfluidity.
Main Methods:
- Numerically exact quantum Monte Carlo calculations.
- Analysis of indirect exciton (IX) energy shifts as a function of density imbalance.
- Investigation of Berezinskii-Kosterlitz-Thouless (BKT) transitions at finite temperatures.
Main Results:
- Indirect exciton (IX) energy shifts exhibit a nonmonotonic trend with a jump discontinuity at density balance, indicating an interlayer IX molecule gap.
- A cascade of Berezinskii-Kosterlitz-Thouless (BKT) transitions is observed, first to pair superfluidity, then to full superfluidity.
- The findings provide a theoretical interpretation for existing observations in GaAs double quantum well (DQW) structures.
Conclusions:
- Collective interlayer pairing and subsequent pair superfluidity are theoretically predicted and characterized.
- Specific experimental signatures, such as IX energy shifts and BKT transitions, are identified.
- Recommendations for experimental settings in GaAs and transition metal dichalcogenide (TMD) heterostructures are provided for optimal observation.
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