Ultranarrow homogeneous broadening of confined excitons in quantum dots: Effect of the surrounding matrix

Ikezawa, Michio; Masumoto, Yasuaki

doi:10.1103/physrevb.61.12662

Cited by 42 publications

(23 citation statements)

References 23 publications

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“…These results are similar to the previous report of CuCl QDs [5] except the LO-phonon contribution. Now, let us consider the dephasing mechanism of the exciton in CuBr/NaBr and CuBr/glass QDs below 15 K. Carrier trapping at the surface of dots produces more than one ground states of the total system consisting of QDs and host materials [9].…”

Section: Resultssupporting

confidence: 94%

“…This is equivalent to the two-level system (TLS) model [10] that has successfully accounted for many anomalous low-temperature properties of glasses. When the energy of TLS is represented by the characteristic energy δ, the homogeneous broadening is in proportion to cosh -2 (δ/2k B T), while T-linear dependence is derived for widely distributed TLS energy [5]. In our case, δ = 2.8 meV is obtained for CuBr/NaBr QDs as a fitting parameter.…”

Section: Resultsmentioning

confidence: 99%

“…Linear temperature broadening or activation type nonlinear temperature broadening was contradictorily reported in the selfassembled quantum dots [3,4]. On the other hand, two-phonon Raman process of confined acoustic phonons was reported in CuCl QDs in the weak confinement regime [5,6]. In Ref.…”

mentioning

confidence: 97%

“…In Ref. [5], smaller energy excitation process in the two-level system (TLS), which is related to surrounding matrix of QDs, was proposed besides. Two-acoustic-phonon process alone was also reported in CdSe QDs embedded in polymer [7].…”

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confidence: 99%

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Low‐temperature dephasing mechanism of very small quantum dots: the role of confined phonons and surrounding matrices

Takemoto

Ikezawa

Masumoto

2003

phys. stat. sol. (c)

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PACS 78.47.+p, 78.67.Hc Temperature dependence of the homogeneous linewidth of CuBr quantum dots in glass and NaBr matrices and CdSe quantum dots in glass matrix has been investigated using heterodyne-detected accumulated photon echo. We can reproduce the observed nonlinear temperature dependence considering two characteristic mechanisms: the small energy excitation in two-level system and the two-phonon Raman process of confined acoustic phonons. The interaction with the two-level system is dominant below 15 K and 10 K for CuBr and CdSe quantum dots, respectively. Above these temperatures the interaction with confined phonons is dominant. These results are similar to those of a previous study of CuCl quantum dots in glass, showing the universal influence of confined phonons and surrounding matrices on the lowtemperature dephasing process of very small semiconductor quantum dots.1 Introduction Semiconductor quantum dots (QDs) are promising candidates for all optical implementation of quantum information processing because of their sharp discrete spectra and very long dephasing time [1,2]. Dephasing time ranging from tens of picoseconds to a nanosecond of I -VII, II-VI and III-V semiconductor QDs are reported recently [3 -7]. From the fundamental physical point of view, it is most important to fully understand the mechanism which restricts the optical coherence time. So far, temperature dependence of homogeneous linewidth has been widely investigated to clarify the dephasing mechanism of QDs, however, serious difference was present in understanding them. Linear temperature broadening or activation type nonlinear temperature broadening was contradictorily reported in the selfassembled quantum dots [3,4]. On the other hand, two-phonon Raman process of confined acoustic phonons was reported in CuCl QDs in the weak confinement regime [5,6]. In Ref.[5], smaller energy excitation process in the two-level system (TLS), which is related to surrounding matrix of QDs, was proposed besides. Two-acoustic-phonon process alone was also reported in CdSe QDs embedded in polymer [7]. The possible difference between these results seems to arise from the different condition whether phonon confinement occurs or not. To clarify the role of confined phonon and surrounding matrix, which should affect the homogeneous linewidth for very small quantum dots, systematic investigation is needed using different kinds of QDs whose acoustic phonons are confined. In this work, we studied CuBr QDs in NaBr and glass matrices in the weak or intermediate confinement regime as well as CdSe QDs in glass matrix in the strong confinement regime at very low temperatures.

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Section: Resultssupporting

confidence: 94%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 97%

mentioning

confidence: 99%

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Low‐temperature dephasing mechanism of very small quantum dots: the role of confined phonons and surrounding matrices

Takemoto

Ikezawa

Masumoto

2003

phys. stat. sol. (c)

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“…In order to show the phenomena clearly, we assume γ = 2 µeV, which is near the smallest value observed under cryogenic conditions [10]. This value is considerably smaller than the calculated radiative width the linear response regime.…”

Section: Collective Effects In Radiation Force Exerted On Plural Sphementioning

confidence: 98%

Collective effects in radiation force on movable quantum dots

Iida

Ishihara

2006

Physica Status Solidi (b)

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We theoretically study the resonant radiation force (RF) exerted on interacting quantum dots (QDs). For this purpose, the analytical expression of RF is derived based on the nonlocal theory and the Lorentz force equation. This explicitly shows how RF on QDs behaves under optical excitation of photomediated coupled-states of polaritons in respective QDs confining excitons. In particular, if three QDs are aligned perpendicular to the optical axis, the negative dissipative (scattering and absorbing) force, whose direction is opposite to the light propagation direction, is exerted on the middle QD due to the phase inversion of the induced polarization in it. Furthermore, indirect attractive and repulsive forces arise between QDs at both ends via the middle QD. These effects would enable us to control the spatial dynamics of a QD-assembly by exciting their collective modes.

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