Research

Magnetic field induced polarization enhancement in monolayers of tungsten dichalcogenides: effects of temperature T. Smoleński, T. Kazimierczuk, M. Goryca, M. R. Molas, K. Nogajewski, C. Faugeras, M. Potemski, P. Kossacki Phys. Rev. X 6, 021024 (2016)

Optical orientation of localized/bound excitons is shown to be effectively enhanced by the application of magnetic fields as low as 20 mT in monolayer WS₂. At low temperatures, the evolution of the polarization degree of different emission lines of monolayer WS₂ with increasing magnetic fields is analyzed and compared to similar results obtained on a WSe₂ monolayer. We study the temperature dependence of this effect up to T=60 K for both materials, focusing on the dynamics of the valley pseudospin relaxation.

Tuning Valley Polarization in a WSe₂ Monolayer with a Tiny Magnetic Field T. Smoleński, M. Goryca, M. Koperski, C. Faugeras, T. Kazimierczuk, A. Bogucki, K. Nogajewski, P. Kossacki, M. Potemski Phys. Rev. X 6, 021024 (2016)

The electron-hole pairs in monolayers of transition metal dichalcogenides exhibit a novel degree of freedom, so called valley pseudospin, that might be exploited to store the quantum information. Here we show that dark excitons can store the information on their valley pseudospin for orders of magnitude longer than previously studied bright excitons in a WSe₂ monolayer.

Giant Rydberg excitons in the copper oxide Cu₂O
T. Kazimierczuk, D. Fröhlich, S. Scheel, H. Stolz, M. Bayer
Nature, 514, 343-347 (2014)

In this work we present results of exciton absorption measurements on bulk Cu₂O. We show the longest hydrogen-like excitonic series reported so far. We observed excitons with principal number n up to 25, which corresponds to exciton extension more than 1μm.

Optical study of electron-electron exchange interaction in CdTe/ZnTe quantum dots
T. Kazimierczuk, T. Smoleński, J. Kobak, M. Goryca, W. Pacuski, A. Golnik, K. Fronc, Ł. Kłopotowski, P. Wojnar, and P. Kossacki
Phys. Rev. B 87, 195302 (2013)

I participated in a number of research projects on different aspects of physics of excitons in quantum dots (QDs). In particular, in this work we investigated the fingerprints of the electron-electron exchange interaction in the photoluminescence spectrum of CdTe/ZnTe QDs. We identified transitions originating from both triplet and singlet configurations of doubly charged exciton X^2-, which allowed us to determine the exchange constant between them as 20 meV.

Excitation of complex spin dynamics patterns in a quantum-dot electron spin ensemble
S. Varwig, I. A. Yugova, A. Rene, T. Kazimierczuk, A. Greilich, D. R. Yakovlev, D. Reuter, A. D. Wieck, and M. Bayer
Phys. Rev. B 90, 121301(R) (2014)

Pump-probe techniques like Time-Resolved Faraday Rotation are a useful tool to study spin dynamics on pico- and nanosecond scale. In this work we show report on unexpected features in such experiment: emergence of a oscillatory signal at double, triple and quadruple of electron Larmor precession frequency.