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Oscillator strengths of dark charged excitons in the quantum Hall regime

C. Schueller·K. -B. Broocks·Ch. Heyn·D. Heitmann
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Abstract

By direct absorption spectroscopy and comparison to photoluminescence (PL), we investigate negatively charged excitons in dilute two-dimensional electron systems at temperatures down to T=40 mK in the regime of the fractional quantum Hall effect. At very low temperatures, for filling factor ν< 1/3, an additional excitation appears in the PL spectrum, between the well-known singlet and triplet excitons. The observation of a similar excitation by PL was reported very recently [G. Yusa et al., cond-mat0103561], and the excitation was assigned, in spite of a PL intensity similar to that of the neutral exciton, to be due to a dark triplet exciton. By comparing PL and direct absorption spectra in optically thin samples at T<100 mK, we can identify the new excitation indeed as a 'dark' mode, since we find that the oscillator strength is much smaller than those of the 'bright' modes.

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C. Schueller, K. -B. Broocks, Ch. Heyn, D. Heitmann. 2001-10-08. Oscillator strengths of dark charged excitons in the quantum Hall regime. https://arxiv.org/abs/cond-mat/0110152

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