Fifth-order two-quantum absorptive two-dimensional electronic spectroscopy of CdSe quantum dots

Abstract

Two-quantum variants of two-dimensional electronic spectroscopy (2DES) have previously been used to characterize multi-exciton interactions in molecules and semiconductor nanostructures though many implementations are limited by phasing procedures or nonresonant signals. We implement 2DES using phase-cycling to simultaneously measure one-quantum and two-quantum spectra in colloidal CdSe quantum dots. In the pump-probe geometry, fully absorptive spectra are automatically acquired by measuring the sum of the rephasing and nonrephasing signals. Fifth-order two-quantum spectroscopy allows for direct access to multi-exciton states that may be obscured in excited state absorption signals due to population relaxation or third-order two-quantum spectra due to the non-resonant response.

Observing Multiexciton Correlations in Colloidal Semiconductor Quantum Dots via Multiple-Quantum Two-Dimensional Fluorescence Spectroscopy

“…We thus choose magnitude spectra in the following to avoid the phase-twisted representation . Dispersive components can in principle be eliminated by summing the real parts of both rephasing and nonrephasing 2Q contributions, leading to purely absorptive 2Q spectra, which necessitates the measurement of higher-order processes. , …”

“…71 Dispersive components can in principle be eliminated by summing the real parts of both rephasing and nonrephasing 2Q contributions, leading to purely absorptive 2Q spectra, which necessitates the measurement of higher-order processes. 48,53 In the experiment shown in Figure 2d, we chose our excitation spectrum (top, red shaded area) to selectively excite |X 1 ⟩ (purple), which in turn leads to the formation of the ground-state biexciton |X 1 X 1 ⟩ through double excitation. The resulting 1Q−2Q 2D spectrum (bottom) thus shows a single feature at the resonance energy of |X 1 ⟩ (purple dashed line) along the 1Q energy axis, being slightly shifted below the diagonal as is typical for a bound biexciton.…”

“…In contrast to both techniques, the most direct measurement of multiexciton states can be realized by probing multiple-quantum coherences, that is, coherent superpositions of the ground state with biexciton and triexciton states . These multiple-quantum 2D spectroscopies have been demonstrated on solid-state semiconductors using coherent signal detection. − Coherently detected fifth-order two-quantum 2D spectroscopy on colloidal CdSe quantum dots was reported very recently . However, the application of multiple-quantum 2D spectroscopy to colloidal quantum dots is generally challenging because of solvent artifacts.…”

“…42−47 Coherently detected fifth-order twoquantum 2D spectroscopy on colloidal CdSe quantum dots was reported very recently. 48 However, the application of multiple-quantum 2D spectroscopy to colloidal quantum dots is generally challenging because of solvent artifacts. Fluorescence-based 2D spectroscopy 49−51 is an alternative to coherently detected 2D spectroscopy.…”

Триэкситоны И Их Влияние На Поглощение В Экситонной Области Спектра

“…Одним из наиболее исследуемых вопросов квантовой оптики является взаимодействие мультиэкситонов с электромагнитнымполем в режиме сильной связи при изменяющихся частотах Раби [12]. В [13] экспериментально исследована электронная структура мультиэкситонов с ограниченным квантованием в коллоидных квантовых точках CdSe. Показано, что в зависимости от энергии и интенсивности возбуждения, можно наблюдать биэкситон и триэкситон, проявляющие яркие связанные состояния, которые являются результатом экситон-экситонного взаимодействия.…”