Mikas Remeika

Condensation of excitons in a trap.

Condensation is observed in a gas of indirect excitons confined in an electrostatic trap. Imaging and interferometric measurements detect that excitons condense at the trap bottom and exciton spontaneous coherence emerges with lowering temperature. Below a temperature of about 1 K, the direct signature of Bose-Einstein condensation, the extension of coherence over the entire cloud, is observed.

Localization-Delocalization Transition of Indirect Excitons in Lateral Electrostatic Lattices

We study transport of indirect excitons in GaAs/AlGaAs coupled quantum wells in linear lattices created by laterally modulated gate voltage. The localization-delocalization transition for transport across the lattice was observed with reducing lattice amplitude or increasing exciton density. The exciton interaction energy at the transition is close to the lattice amplitude. These results are consistent with the model, which attributes the localization-delocalization transition to the interaction-induced percolation of the exciton gas through the external potential. We also discuss applications of the lattice potentials for estimating the strength of disorder and exciton interaction.

Optically controlled excitonic transistor

We present experimental proof of principle for all-optical excitonic routers and all-optical excitonic transistors with a high ratio between the excitonic signal at the optical drain and the excitonic signal due to the optical gate.

Trapping Indirect Excitons in a GaAs Quantum-Well Structure with a Diamond-Shaped Electrostatic Trap

We report on the principle and realization of a new trap for excitons – the diamond electrostatic trap – which uses a single electrode to create a confining potential for excitons. We also create elevated diamond traps which permit evaporative cooling of the exciton gas. We observe collection of excitons towards the trap center with increasing exciton density. This effect is due to screening of disorder in the trap by the excitons. As a result, the diamond trap behaves as a smooth parabolic potential which realizes a cold and dense exciton gas at the trap center.

All-optical excitonic transistor

We demonstrate experimental proof of principle for all-optical excitonic transistors where light controls light by using excitons as an intermediate medium. The principle of operation of all-optical excitonic transistors is based on the control of exciton fluxes by light.

Two-dimensional electrostatic lattices for indirect excitons

We report on a method for the realization of two-dimensional electrostatic lattices for excitons using patterned interdigitated electrodes. Lattice structure is set by the electrode pattern and depth of the lattice potential is controlled by applied voltages. We demonstrate square, hexagonal, and honeycomb lattices created by this method.

Pattern formation in the exciton inner ring

We report on pattern formation in the exciton inner ring. The effect is explained in terms of exciton transport and thermalization.

Transport of indirect excitons in a potential energy gradient

We create a potential energy gradient for indirect excitons using a shaped electrode and study exciton transport. We observe that indirect excitons are localized at low densities and travel along the ramp at high densities.

Measurement of exciton correlations using electrostatic lattices

We present a method for determining correlations in a gas of indirect excitons. The method involves subjecting the excitons to an electrostatic lattice. We present findings of strong correlations in systems of indirect excitons.

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Condensation is observed in a gas of indirect excitons confined in an electrostatic trap. Imaging and interferometric measurements detect that excitons condense at the trap bottom and exciton spontaneous coherence emerges with lowering temperature. Below a temperature of about 1 K, the direct signature of Bose−Einstein condensation, the extension of coherence over the entire cloud, is observed.