Measurement of exciton correlations using electrostatic lattices

We present a method for determining correlations in a gas of indirect excitons in a semiconductor quantum well structure. The method involves subjecting the excitons to a periodic electrostatic potential that causes modulations of the exciton density and photoluminescence (PL). Experimentally measured amplitudes of energy and intensity modulations of exciton PL serve as an input to a theoretical estimate of the exciton correlation parameter and temperature. We also present a proof-of-principle demonstration of the method for determining the correlation parameter and discuss how its accuracy can be improved.Comment: 10 pages, 11 figure

Exciton gas transport through nano-constrictions

An indirect exciton is a bound state of an electron and a hole in spatially separated layers. Two-dimensional indirect excitons can be created optically in heterostructures containing double quantum wells or atomically thin semiconductors. We study theoretically transmission of such bosonic quasiparticles through nano-constrictions. We show that quantum transport phenomena, e.g., conductance quantization, single-slit diffraction, two-slit interference, and the Talbot effect, are experimentally realizable in systems of indirect excitons. We discuss similarities and differences between these phenomena and their counterparts in electronic devices.Comment: (v2) Updated title, text, and references; 12 pages, 9 figure

Doping-Dependent Raman Resonance in the Model High-Temperature Superconductor HgBa2CuO4+d

We study the model high-temperature superconductor HgBa2CuO4+d with electronic Raman scattering and optical ellipsometry over a wide doping range. The resonant Raman condition which enhances the scattering cross section of "two-magnon" excitations is found to change strongly with doping, and it corresponds to a rearrangement of inter-band optical transitions in the 1-3 eV range seen by ellipsometry. This unexpected change of the resonance condition allows us to reconcile the apparent discrepancy between Raman and x-ray detection of magnetic fluctuations in superconducting cuprates. Intriguingly, the strongest variation occurs across the doping level where the antinodal superconducting gap reaches its maximum.Comment: 4 pages, 4 figures, contact authors for Supplemental Materia

Transport of indirect excitons in high magnetic fields

We present spatially and spectrally resolved photoluminescence measurements of indirect excitons in high magnetic fields. Long indirect exciton lifetimes give the opportunity to measure magnetoexciton transport by optical imaging. Indirect excitons formed from electrons and holes at zeroth Landau levels (0e−0h indirect magnetoexcitons) travel over large distances and form a ring emission pattern around the excitation spot. In contrast, the spatial profiles of 1e−1h and 2e−2h indirect magnetoexciton emission closely follow the laser excitation profile. The 0e−0h indirect magnetoexciton transport distance reduces with increasing magnetic field. These effects are explained in terms of magnetoexciton energy relaxation and effective mass enhancement

Indirect excitons in a potential energy landscape created by a perforated electrode

We report on the principle and realization of an excitonic device: a ramp that directs the transport of indirect excitons down a potential energy gradient created by a perforated electrode at a constant voltage. The device provides an experimental proof of principle for controlling exciton transport with electrode density gradients. We observed that the exciton transport distance along the ramp increases with increasing exciton density. This effect is explained in terms of disorder screening by repulsive exciton-exciton interactions