13 research outputs found
Biexcitons in two-dimensional systems with spatially separated electrons and holes
The binding energy and wavefunctions of two-dimensional indirect biexcitons
are studied analytically and numerically. It is proven that stable biexcitons
exist only when the distance between electron and hole layers is smaller than a
certain critical threshold. Numerical results for the biexciton binding
energies are obtained using the stochastic variational method and compared with
the analytical asymptotics. The threshold interlayer separation and its
uncertainty are estimated. The results are compared with those obtained by
other techniques, in particular, the diffusion Monte-Carlo method and the
Born-Oppenheimer approximation.Comment: 11 pages, 7 figure
Collection of indirect excitons in 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.Comment: 4 Pages, 5 figure
Concentration-dependent mobility in organic field-effect transistors probed by infrared spectromicroscopy of the charge density profile
We show that infrared imaging of the charge density profile in organic
field-effect transistors (FETs) can probe transport characteristics which are
difficult to access by conventional contact-based measurements. Specifically,
we carry out experiments and modeling of infrared spectromicroscopy of
poly(3-hexylthiophene) (P3HT) FETs in which charge injection is affected by a
relatively low resistance of the gate insulators. We conclude that the mobility
of P3HT has a power-law density dependence, which is consistent with the
activated transport in disorder-induced tails of the density of states.Comment: 3+ pages, 2 figure
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 (LDT) 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 LDT 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.Comment: 4 pages, 4 figure