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1

Ultrafast Coherent Terahertz Spectroscopy in High Magnetic Fields and Directed Energy Flows in Quantum Dot Assemblies

100%

Crooker S., Barrick T., Hollingsworth J., Klimov V.

Acta Physica Polonica A

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2003

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vol. 104

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issue 2

113-122

EN

We describe the design, construction, and use of fiber-coupled terahertz antennas for performing ultrafast coherent THz spectroscopy directly in the cryogenic bore of high-field magnets. With an aim towards measuring the high-frequency (100 GHz to 2000 GHz) complex conductivity of correlated electron materials in the regime of low temperatures and high magnetic fields, these miniature THz emitters and receivers are demonstrated to work down to 1.5 K and up to 18 T, for eventual use in higher-field magnets. Results from a variety of semiconducting and superconducting samples are presented. This paper also describes a separate effort towards achieving coupling between colloidal semiconductor nanocrystal quantum dots, wherein we realize and study inter-dot communication via resonant (Förster) energy transfer. We present studies of the dynamics of resonant energy transfer in monodisperse and energy gradient (layered) assemblies of CdSe nanocrystal quantum dots. Time- and spectrally-resolved photoluminescence data directly reveal the energy-dependent transfer rate of excitons from smaller to larger dots. Results from layered nanocrystal quantum dot assemblies demonstrate unidirectional energy flows, a first step towards artificial light-harvesting structures. Lastly, time-resolved studies at millikelvin temperatures elucidate the nature of ground-state"dark" excitons in these quantum dots.

2

Temperature Dependence of Exciton and Trion States in CdTe Quantum Well at High Magnetic Fields

88%

Andronikov D., Platonov A., Crooker S., Barrick T., Karczewski G.

Acta Physica Polonica A

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2005

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vol. 108

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issue 4

653-660

EN

Temperature dependent photoluminescence and reflectivity spectra of excitons, singlet and triplet states of trions were studied in CdTe-based quantum wells at high magnetic fields. Interesting features of the exciton and trion spectral lines with altering temperatures are explained by analyzing the thermal population and the kinetics of the exciton-electron-trion energetic system.

3

Excitons and Trions in Modulation Doped Structures in High Magnetic Fields

76%

Kochereshko V., Andronikov D., Platonov A., Crooker S., Barrick T., Karczewski G., Tronc P.

Acta Physica Polonica A

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2004

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vol. 106

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issue 3

319-328

EN

Photoluminescence spectra of modulation-doped CdTe/CdMgTe quantum well structures containing two-dimensional electron gases of low, moderate and high electron concentrations were studied in high magnetic fields up to 45 T. The recombination line of triplet trion state was found in the spectra. A model calculation of photoluminescence spectra in magnetic fields, which takes into account singlet and triplet trion states, was carried out. It was shown that the dark triplet becomes observable in photoluminescence spectra because it becomes the only recombination channel when the formation of the singlet trion state is suppressed by magnetic fields.

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3 Acta Physica Polonica A

1 2005

1 2004

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3 Barrick T.

3 Crooker S.

2 Andronikov D.

2 Karczewski G.

2 Platonov A.

1 Hollingsworth J.

1 Klimov V.

1 Kochereshko V.

1 Tronc P.

Ultrafast Coherent Terahertz Spectroscopy in High Magnetic Fields and Directed Energy Flows in Quantum Dot Assemblies

Temperature Dependence of Exciton and Trion States in CdTe Quantum Well at High Magnetic Fields

Excitons and Trions in Modulation Doped Structures in High Magnetic Fields