Quadexciton cascade and fine-structure splitting of the triexciton in a single quantum dot

Abstract

We report the properties of emission lines associated with the cascaded recombination of a quadexciton in single GaAlAs/AlAs quantum dots, studied by means of polarization-resolved photoluminescence and single-photon correlation experiments. It is found that photons which are emitted in a double-step 4X-3X process preserve their linear polarization, similarly to the case of conserved polarization of correlated photons in the 2X-X cascade. In contrast, an emission of either co-linear or cross-linear pairs of photons is observed for the 3X-2X cascade. Each emission line associated with the quadexciton cascade shows doublet structure in the polarization-resolved photoluminescence experiment. The maximum splitting is seen when the polarization axis is chosen along and perpendicular to the [110] crystallographic direction. This effect is ascribed to the fine structure splitting of the exciton and triexciton states in the presence of an anisotropic confining potential of ae dot. We also show that the splitting in the triexciton state surpasses that in the exciton state by a factor up to eight and their ratio scales with the energy distance between the 3X and X emission lines, thus, very likely, with a lateral size and/or a composition of the dot.

Energy spectrum of confined positively charged excitons in single quantum dots

“…These dots show remarkably low surface density, at the level of 10 5 − 10 6 cm −2 . Their emission spectra are dispersed in a wide energy range, 1.56-1.68 eV, [14][15][16][17][18][19][20] due to the spread in the lateral extent of the confining potential.…”

Influence of the quantum dot geometry on p -shell transitions in differently charged quantum dots

“…Most studies focus on the QD ground states in the prospect of several possible applications within the fields of quantum computing [1], advanced photon sources [2][3][4] and spintronics [5]. Less is known about the higher excited level structure, which is vital for the understanding of time-resolved phenomena like relaxation and dephasing mechanisms [6][7][8], recombinations of multiexcitons with more than two electrons or holes [9][10][11][12][13][14][15][16][17] or resonant absorption characteristics, typically measured via photoluminescence excitation (PLE) spectroscopy [6,[18][19][20].…”

Триэкситоны И Их Влияние На Поглощение В Экситонной Области Спектра

“…Наличие экситонных, биэкситонных, триэкситонных и мультиэкситонных состояний [1,2] и возможность селективного управления их свойствами под действием когерентного лазерного излучения во многом определяют оптические характеристики полупроводниковых структур и, следовательно, стимулируют развитие передовых исследований во многих областях: квантовой обработки информации, создании энергоэффективных электронных устройств, конфокальной микроскопии [3], поляритонной генерации, бозе-эйнштейновской конденсации экситон поляритонов [4], поляритонной сверхтекучести. Обнаружение экситонов с большими квантовыми числами [5], являющиеся аналогами ридберговских атомов позволяют изучать новые эффекты, которые не наблюдаются в физике атомов, так как энергии связи ридберговских состояний экситона малы и экситоны более чувствительны к воздействию внешних электрических и магнитных полей, поэтому при изменении интенсивности внешнего поля можно наблюдать многообразие сдвигов и пересечений уровней поглощения.…”