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Projects A1-A8

A [1] [3] [4] [5] [6] [7] [8]     B [1] [2] [3] [4] [6] [7] [8] [9]     C [1] [2] [5] [7] [8] [9]     Z [3] [4]

 

A1 Coherent manipulation of complex spin ensembles in semiconductor nanostructures

Principal investigators:

Associated: Dr. Alex Greilich (TU Dortmund)

Summary:

The project focuses on tailoring the precession of spins in a quantum dot ensemble and exploring the interactions between different spin ensembles. The variability provided by a spin ensemble shall be exploited to generate and study spin mode distributions with complex dynamics. Furthermore, based on a microscopic understanding of the spin-spin interaction, we plan to optimize the interaction strength for obtaining spin states with robust entanglement. Based on these methods, tools for coherent manipulation of interacting and entangled spin states shall be worked out, for which also the potential of dynamic decoupling tools will be elaborated.

 

A3 Transient four-wave mixing with spins

Principal investigators:

Summary:

The project focuses on photon echo phenomena involving semiconductor nanostructures (quantum wells and quantum dots) with localized resident carriers subject to external magnetic fields. The goal is to combine optical and spin excitations in an inhomogeneously broadened system to realize long-lived optical quantum memories. The interaction of resonant optical pulses with fundamental optical excitations such as excitons or trions with well-defined spin level structure will be explored. Stimulated and spontaneous photon echoes will be analyzed using transient four-wave mixing with heterodyne detection.

 

A4 Coherent control of the electronic and nuclear spins in quantum dot ensembles

Principal investigators:

Summary:

The project is focused on the quantitative theoretical description of coherent control and dynamic spin polarization in ensembles of quantum dots induced by ultrafast pumping by optical laser pulses. We describe the radiative decay of the intermediate trion states simultaneously considering the hyperfine coupling to baths of various nuclear spins due to the presence of different isotopes, the dipole-dipole interaction among the nuclear spins, and the nuclear quadrupolar interaction induced by strain fields. Quantum mechanical and semi-classical techniques combined with stochastic approaches will be employed to assess the effect of trains of pulses and to suggest protocols for spin manipulation. Novel foci are interactions between the spins of different quantum dots and spin inertia as measured by the laser pulses with modulated circular polarization. We will study both conventional quantum dots from III-V semiconductors as well as novel types of nanosystems such as organic/inorganic perovskites.

 

A5 Basic problems of spin-noise signal formation

Principal investigators:

Associated: Dr. Alex Greilich (TU Dortmund)

Summary:

This project is aimed to study the influence of external perturbations on spin systems in thermal equilibrium by the spin noise methodology. We want to provide comparative studies of unperturbed vs. perturbed spin systems, for which the perturbations are provided either by optical illumination or by radio-frequency fields influencing the nuclear surrounding of localized carriers. Furthermore, we plan to develop cavity-enhanced spin noise spectroscopy and apply it to different spin systems with the goal to detect magnetic resonances and study the dynamics of spins through higher order correlations.

 

A6 Impact of nuclear spin cooling on carrier spin coherence

Principal investigators:

Associated: Dr. Maria Kusnetzova, Dr. Mikhail Petrov, and Prof. Dr. Sergey Verbin (St. Petersburg State University) as well as Prof. Dr. Vladimir Kalevich (Ioffe Institute)

Summary:

This project investigates nuclear spin fluctuations, effects of quadrupole splitting of nuclear spin states, spin-lattice relaxation and decoherence in the nuclear spin system of semiconductors. For this purpose, the nuclear spin polarization will be enhanced by dynamic polarization via spin-oriented electrons. Optically detected magnetic resonance will be used to determine the evolution of the nuclear spins in magnetic fields and their back-action on the central electron spin of a localized charge carrier. The role of quadrupole splittings of nuclear spin states, which may considerably affect the nuclear-nuclear and electron-nuclear spin dynamics and carrier spin coherence, will also be studied.

 

A7 Theory of spin-noise in semiconductor quantum dots

Principal investigators:

Summary:

Spin-noise spectroscopy is an important technique for revealing the microscopic nature of spin decoherence in quantum dots. For its theoretical descriptions, isotropic and anisotropic variants of the central spin model will be investigated. Issues to be addressed are quantum mechanical effects in large spin baths, the computation of higher order correlators such as four-point correlators, and the description of nuclear spin noise and the correlations of the nuclear spins of different sub-ensembles. Furthermore, we want to address diluted baths, i.e., baths of small numbers of nuclear spins, and how they can be manipulated and how specific states of them can be prepared. We will also study correlations between the electron and nuclear spins and microscopic scenarios of nuclear polaron formation.

 

A8 Interacting Rydberg excitons in modulated potential landscapes

Principal investigators:

Associated: Dr. Philipp Grigoryev, Dr. Gleb Kozlov, and Dr. Artur Trifonov (St. Petersburg State University

Summary:

Rydberg excitons with wavefunction extensions up into the μm-range are attractive for studying confinement and interaction effects on much larger length scales than ground state excitons, which typically can be confined in nanostructures only. Recent studies of Rydberg excitons in cuprous oxide have demonstrated that an accurate description of these effects requires the inclusion of band structure details and, in particular, exciton orbital and spin angular momenta. With our current understanding obtained on bulk crystals, we will attempt to tailor the interactions by exciting excitons in designed potential landscapes which can be created, for example, by varying the size and geometry of the sample, by applying strain to crystal slabs through shaped pistons, or by optical lattices formed by counter-propagating laser beams. With these tools, potentials with extensions comparable to the Rydberg exciton size can be achieved. Besides cuprous oxide, we will study wide (bulk-like) GaAs quantum wells for comparison, providing different optical selection rules.


 

Sub content

Contact

ICRC - TRR 160
Katharina Sparka
Technische Universität Dortmund
Otto-Hahn-Straße 4a
D-44227 Dortmund
Germany

 

Office

Phone +49 (0)231 755 2041
Fax +49 (0)231 755 3674

 

Arrival

Chair's arrival description