T. Kazimierczuk

Optical manipulation of a single Mn spin in a CdTe-based quantum dot.

Two coupled CdTe quantum dots, selected from a self-assembled system, one of them containing a single Mn ion, were studied by continuous wave and modulated photoluminescence, photoluminescence excitation, and photon correlation experiments. Optical writing of information on the spin state of the Mn ion has been demonstrated, using the orientation of the Mn spin by spin-polarized carriers transferred from the neighboring quantum dot. Mn spin orientation time values from 20 to 100 ns were measured, depending on the excitation power. Storage time of the information on the Mn spin was found to be enhanced by application of a static magnetic field of 1 T, reaching hundreds of microseconds in the dark. Simple rate equation models were found to describe correctly the static and dynamical properties of the system.

Giant Rydberg excitons in the copper oxide Cu2O

A highly excited atom having an electron that has moved into a level with large principal quantum number is a hydrogen-like object, termed a Rydberg atom. The giant size of Rydberg atoms leads to huge interaction effects. Monitoring these interactions has provided insights into atomic and molecular physics on the single-quantum level. Excitons—the fundamental optical excitations in semiconductors, consisting of an electron and a positively charged hole—are the condensed-matter analogues of hydrogen. Highly excited excitons with extensions similar to those of Rydberg atoms are of interest because they can be placed and moved in a crystal with high precision using microscopic energy potential landscapes. The interaction of such Rydberg excitons may allow the formation of ordered exciton phases or the sensing of elementary excitations in their surroundings on a quantum level. Here we demonstrate the existence of Rydberg excitons in the copper oxide Cu2O, with principal quantum numbers as large as n = 25. These states have giant wavefunction extensions (that is, the average distance between the electron and the hole) of more than two micrometres, compared to about a nanometre for the ground state. The strong dipole–dipole interaction between such excitons is indicated by a blockade effect in which the presence of one exciton prevents the excitation of another in its vicinity.

Slowing hot-carrier relaxation in graphene using a magnetic field

A degenerate pump-probe technique is used to investigate the nonequilibrium carrier dynamics in multilayer graphene. Two distinctly different dynamics of the carrier relaxation are observed. A fast relaxation

Excitation mechanisms of individual Cd Te ∕ Zn Te quantum dots studied by photon correlation spectroscopy

(\ensuremath{\sim}50\text{ }\text{fs})

Optically induced energy and spin transfer in nonresonantly coupled pairs of self-assembled CdTe/ZnTe quantum dots

of the carriers after the initial effect of phase-space filling followed by a slower relaxation

Picosecond charge variation of quantum dots under pulsed excitation

(\ensuremath{\sim}4\text{ }\text{ps})

Magnetic ground state of an individual Fe 2+ ion in strained semiconductor nanostructure

due to thermalization. Both relaxation processes are less efficient when a magnetic field is applied at low temperatures which is attributed to the suppression of the electron-electron Auger scattering due to the nonequidistant Landau-level spacing of the Dirac fermions in graphene.

Brightening of dark excitons in a single CdTe quantum dot containing a single Mn2+ ion

Systematic measurements of auto- and cross-correlations of photons emitted from individual

Magnetic polaron formation and exciton spin relaxation in single Cd1-xMnxTe quantum dots

\mathrm{Cd}\mathrm{Te}∕\mathrm{Zn}\mathrm{Te}

Magnetophotoluminescence study of intershell exchange interaction in CdTe/ZnTe quantum dots

quantum dots under pulsed excitation were used to elucidate nonresonant excitation mechanisms in this self-assembled system. Memory effects extending over a few excitation pulses have been detected in agreement with previous reports and quantitatively described by a rate equation model, fitting a complete set of correlation and PL intensity results. The important role of single carrier trapping in the quantum dot was established. An explanation was suggested for the unusually wide antibunching dip observed previously in