arXiv subjects

Michal Zimmerman

Publications and source records attributed to Michal Zimmerman.

4 recordsLinked to original sources

arXiv2025

Quadrupolar and dipolar phases of excitons in transition-metal dichalcogenide trilayer heterostructures

Recent experiments on trilayer transition-metal dichalcogenide heterostructures have revealed the rich behavior of dipolar excitons. Motivated by these experimental observations, we investigate the collective dynamics of planar quantum dipoles whose orientation fluctuates due to charge tunneling between the outer layers. Using large-scale quantum Monte Carlo simulations, we map out the low-temperature phase diagram as a function of experimentally tunable parameters. We uncover a diverse landscape of phases driven by dipolar correlations. Under strong dipole fluctuations, a quadrupolar superfluid emerges. Suppressing charge tunneling nucleates a droplet state stabilized by the attractive interaction between antiparallel dipoles. At high exciton densities, the system gives way to a partially fragmented condensate, characterized by competing quadrupolar and dipolar superfluid states. Furthermore, at a large exciton mass and high density, we find a staggered dipolar crystal. Our detailed study of the dependence of exciton energy shifts on an external electric field directly interprets existing experimental data and underscores the crucial role of the antiparallel dipolar configuration. Our results provide a guide for future experimental explorations of quantum phases of trilayer excitons.

cond-mat.mes-hall↗

arXiv2025

Trimer superfluidity of antiparallel dipolar excitons in a bilayer heterostructure

We study the phase diagram of a bilayer of antiparallel dipolar excitons with a 1:2 density ratio between the layers, as a function of temperature and density. Using quantum Monte Carlo simulations, we show that such a system supports the formation of trimers, namely, three-exciton bound states consisting of a single dipole in one layer and two dipoles in the second layer. At sufficiently low temperatures and densities, these trimers condense into a trimer superfluid phase. Increasing the excitonic density induces a quantum phase transition into a phase in which condensates of independent dipoles exist in both layers, in parallel to the trimers. We also study the thermal transitions out of these phases, and find that while the normal state is reached directly from the trimer superfluid, the thermal disordering of the two-superfluid phase involves an intermediate state which is either a trimer superfluid or a single excitonic condensate in the denser layer. A potential experimental realization using transition metal dichalcogenide heterostructures is discussed.

cond-mat.mes-hall↗

arXiv2024

Reciprocity-assisted ghost imaging through dynamic random media

Ghost imaging enables the imaging of an object using intensity correlations between a single-pixel detector placed behind the object and a camera that records light that did not interact with the object. The object and the camera are often placed at conjugate planes to ensure correlated illumination patterns. Here, we show how the combined effect of optical reciprocity and the memory effect in a random medium gives rise to correlations between two beams that traverse the random medium in opposite directions. Using these correlations, we demonstrate a ghost imaging scheme in which the object and camera are placed at opposite ends of the random medium and illuminated by counter-propagating beams that can potentially be emitted by two different sources.

physics.optics↗

arXiv2022

Collective interlayer pairing and pair superfluidity in vertically stacked layers of dipolar excitons

Layered bosonic dipolar fluids have been suggested to host a condensate of interlayer molecular bound states. However, its experimental observation has remained elusive. Motivated by two recent experimental works [Hubert et al., Phys. Rev. X 9, 021026 (2019) and D. J. Choksy et al., Phys. Rev. B 103 045126 (2021)], we theoretically study, using numerically exact quantum Monte Carlo calculations, the experimental signatures of collective interlayer pairing in vertically stacked indirect exciton (IX) layers. We find that IX energy shifts associated with each layer evolve non trivially as a function of density imbalance following a nonmonotonic trend with a jump discontinuity at density balance, identified with the interlayer IX molecule gap. This behavior discriminates between the superfluidity of interlayer bound pairs and independent dipole condensation in distinct layers. Considering finite temperature and finite density imbalance conditions, we find a cascade of Berezinskii--Kosterlitz--Thouless (BKT) transitions, initially into a pair superfluid and only then, at lower temperatures, into complete superfluidity of both layers. Our results may provide a theoretical interpretation of existing experimental observations in GaAs double quantum well (DQW) bilayer structures. Furthermore, to optimize the visibility of pairing dynamics in future studies, we present an analysis suggesting realistic experimental settings in GaAs and transition metal dichalcogenide (TMD) bilayer DQW heterostructures where collective interlayer pairing and pair superfluidity can be clearly observed.

cond-mat.mes-hall↗