Cheng-Ran Du, Ka-Di Zhu
The quantum oscillations of population in an asymmetric double quantum dots system coupled to a phonon bath are investigated theoretically. It is shown how the environmental temperature has effect on the system.
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The optical properties of quantum dots embedded in a catalytically grown semiconductor nanowire are studied theoretically. In comparison to dots in a bulk environment, the excitonic absorption is strongly modified by the one-dimensional character of the nanowire phonon spectrum. In addition to pronounced satellite peaks due to phonon-assisted absorption, we find a finite width of the zero-phonon line already in the lowest-order calculation.
Existence of representative longitudinal optical (LO) phonon modes is theoretically discussed for the case of polar semiconductor cylindrical quantum dots embedded in a semiconductor matrix. The approach is developed within the dielectric continuum model considering the Fröhlich interaction between electrons and the confined LO phonons. The theory is applied to cylindrical GaAs/AlAs quantum dots within an adiabatic treatment.
Polar optical-phonon modes are derived analytically for spheroidal quantum dots with wurtzite crystal structure. The developed theory is applied to a freestanding spheroidal ZnO quantum dot and to a spheroidal ZnO quantum dot embedded into a MgZnO crystal. The wurtzite (anisotropic) quantum dots are shown to have strongly different polar optical-phonon modes in comparison with zincblende (isotropic) quantum dots. The obtained results allow one to explain and accurately predict phonon peaks in the Raman spectra of wurtzite nanocrystals, nanorods (prolate spheroids), and epitaxial quantum dots (…
Transport through coupled quantum dots in a phonon bath is studied using the recently developed real-time renormalization-group method. Thereby, the problem can be treated beyond perturbation theory regarding the complete interaction. A reliable solution for the stationary tunnel current is obtained for the case of moderately strong couplings of the dots to the leads and to the phonon bath. Any other parameter is arbitrary, and the complete electron-phonon interaction is taken into account. Experimental results are quantitatively reproduced by taking into account a finite extension of the wave…
The dynamics of an exciton-LO-phonon system after an ultrafast optical excitation in an InAs/GaAs quantum dot is studied theoretically. Influence of anharmonic phonon damping and its interplay with the phonon dispersion is analyzed. The signatures of the zone-edge decay process in the absorption spectrum and time evolution are highlighted, providing a possible way of experimental investigation on phonon anharmonicity effects.
Phonons strongly influence the optical control of semiconductor quantum dots. When modeling the electron-phonon interaction in several theoretical approaches the quantum dot geometry is approximated by a spherical structure, though typical self-assembled quantum dots are strongly lens-shaped. By explicitly comparing simulations of a spherical and a lens-shaped dot using a well-established correlation expansion approach we show that indeed lens-shaped dots can be exactly mapped to a spherical geometry when studying the phonon influence on the electronic system. We also give a recipe to reproduc…
Phonon-induced spin relaxation in coupled lateral quantum dots in the presence of spin-orbit coupling is calculated. The calculation for single dots is consistent with experiment. Spin relaxation in double dots at useful interdot couplings is dominated by spin hot spots that are strongly anisotropic. Spin hot spots are ineffective for a diagonal crystallographic orientation of the dots with a transverse in-plane field. This geometry is proposed for spin-based quantum information processing.
We investigate theoretically spin relaxation in heavy hole quantum dots in low external magnetic fields. We demonstrate that two-phonon processes and spin-orbit interaction are experimentally relevant and provide an explanation for the recently observed saturation of the spin relaxation rate in heavy hole quantum dots with vanishing magnetic fields. We propose further experiments to identify the relevant spin relaxation mechanisms in low magnetic fields.
We calculate the electron-phonon interaction coefficients for surface acoustic waves and for phonons in free standing quantum wells. These are used to derive the inelastic current through a double quantum dot caused by spontaneous emission of phonons. For the case of the free standing structure (phonon cavity), we predict a staircase-like inelastic current superimposed by van Hove singularities. Therefore, the phonon confinement can be detected by electron transport measurements.
Longitudinal optical phonons have been used to interpret the electronic energy relaxation in quantum dots and at the same time they served as a reservoir, with which the electronic subsystem is in contact. Such a phonon subsystem is expected to be passive, namely, in a long-time limit the whole system should be able to achieve such a stationary state, in which statistical distributions of both subsystems do not change in time. We pay attention to this property of the LO phonon bath. We show the passivity property of the so far used approximations to electronic transport in quantum dots. Also w…
A theory of photoluminescence in semiconductor quantum dots is developed which relies on two key ingredients. First, it takes into account non-adiabaticity of the exciton-phonon system. Second, it includes the multimode dielectric model of LO-phonons and of the electron-phonon interaction in confined systems. The role of non-adiabaticity is shown to be of paramount importance in spherical quantum dots, where the lowest one-exciton state can be degenerate or quasi-degenerate. For various quantum dot structures, the calculated intensities of phonon satellites as a function of temperature, excita…
We explore electronic transport in a nanotube quantum dot strongly coupled with vibrations and weakly with leads and the thermal environment. We show that the recent observation of anomalous conductance signatures in single-walled carbon nanotube (SWCNT) quantum dots can be understood quantitatively in terms of current driven `hot phonons' that are strongly correlated with electrons. Using rate equations in the many-body configuration space for the joint electron-phonon distribution, we argue that the variations are indicative of strong electron-phonon coupling requiring an analysis beyond the…
We analyzed time evolution of the localized charge in the system of two interacting single level quantum dots (QDs) coupled with the continuous spectrum states in the presence of electron-phonon interaction. We demonstrated that electron-phonon interaction leads to the increasing of localized charge relaxation rate. We also found that several time scales with different relaxation rates appear in the system in the case of non-resonant tunneling between the dots. We revealed the formation of oscillations in the filling numbers time evolution caused by the emission and adsorption processes of pho…
We study and compare two analytic models of graphene quantum dots for calculating charge relaxation times due to electron-phonon interaction. Recently, charge relaxation processes in graphene quantum dots have been probed experimentally and here we provide a theoretical estimate of relaxations times. By comparing a model with pure edge confinement to a model with electrostatic confinement, we find that the latter features much larger relaxation times. Interestingly, relaxation times in electrostatically defined quantum dots are predicted to exceed the experimentally observed lower bound of ~10…
We report on electron transport through an artificial molecule formed by two tunnel coupled quantum dots, which are laterally confined in a two-dimensional electron system of an Al$_x$Ga$_{1-x}$As/GaAs heterostructure. Coherent molecular states in the coupled dots are probed by photon-assisted tunneling (PAT). Above 10 GHz, we observe clear PAT as a result of the resonance between the microwave photons and the molecular states. Below 8 GHz, a pronounced superposition of phonon- and photon-assisted tunneling is observed. Coherent superposition of molecular states persists under excitation of ac…
We study the evolution of a quantum state of a double quantum dot system interacting with the electromagnetic environment and with the lattice modes, in the presence of a coupling between the two dots. We propose a unified approach to the simulation of the system evolution under joint impact of the two reservoirs. We discuss the sub- and superradiant radiative decay of the system, the phonon-induced decay of entanglement between the dots, and the transfer of excitation between them.
This chapter is devoted to the recent theoretical results on the optical quantum control over charges confined in quantum dots under influence of phonons. We show that lattice relaxation processes lead to decoherence of the confined carrier states. The theoretical approach leading to a uniform, compact description of the phonon impact on carrier dynamics, perturbative in phonon couplings but applicable to arbitrary unperturbed evolution, is described in detail. Next, some applications are presented: phonon damping of Rabi oscillations in quantum dots and phonon-induced error of a single-qubit …
We have studied the absorption of electromagnetic radiation of an anisotropic quantum dot taking into account the spin-flip processes that is associated with the interaction of the electrons with optical phonons. It is shown that these processes lead to the resonance absorption. Explicit formula is derived for the absorption coefficient. The positions of the resonances peaks are found.
We have calculated spin relaxation rates in parabolic quantum dots due to the phonon modulation of the spin-orbit interaction in presence of an external magnetic field. Both, deformation potential and piezoelectric electron-phonon coupling mechanisms are included within the Pavlov-Firsov spin-phonon Hamiltonian. Our results have demonstrated that, in narrow gap materials, the electron-phonon deformation potential and piezoelectric coupling give comparable contributions as spin relaxation processes. For large dots, the deformation potential interaction becomes dominant. This behavior is not obs…
We present a theoretical study of the evolution of spatial coherence during relaxation between delocalized exciton states in a pair of vertically stacked semiconductor quantum dots coupled to acoustic phonons. We show that spatial coherence can be transferred to the ground state even in a system of uncoupled non-identical quantum dots if a particular kind of degeneracy between the inter-level energy splittings is present. The phonon-assisted mechanism of coherence transfer leads to a dependence of the amount of the resulting coherence on the inter-dot distance and temperature. We analyze also …
We propose phonon spectroscopy by electric measurements of the low-temperature conductance of coupled-quantum dots, specifically employing dephasing of the quantum electronic transport by the phonons. The setup we consider consists of a T-shaped double-quantum-dot (DQD) system in which only one of the dots (dot 1) is connected to external leads and the other (dot 2) is coupled solely to the first one. For noninteracting electrons, the differential conductance of such a system vanishes at a voltage located in-between the energies of the bonding and the anti-bonding states, due to destructive in…
We calculate the spin relaxation rates in a parabolic InSb quantum dots due to the spin interaction with acoustical phonons. We considered the deformation potential mechanism as the dominant electron-phonon coupling in the Pavlov-Firsov spin-phonon Hamiltonian. By studying suitable choices of magnetic field and lateral dot size, we determine regions where the spin relaxation rates can be practically suppressed. We analyze the behavior of the spin relaxation rates as a function of an external magnetic field and mean quantum dot radius. Effects of the spin admixture due to Dresselhaus contributi…
We have found a novel mechanism of spectral broadening and dephasing in quantum dots (QDs) due to the coupling to longitudinal-optical (LO) phonons. In theory, this mechanism comes into play only if the complete manifold of exciton levels (including those in the wetting-layer continuum) is taken into account. We demonstrate this nontrivial dephasing in different types of QDs, using the exactly solvable quadratic coupling model, here generalized to an arbitrary number of excitonic states.
We propose optical phonon lasing for a double quantum dot (DQD) fabricated in a semiconductor substrate. We show that the DQD is weakly coupled to only two LO phonon modes that act as a natural cavity. The lasing occurs for pumping the DQD via electronic tunneling at rates much higher than the phonon decay rate, whereas an antibunching of phonon emission is observed in the opposite regime of slow tunneling. Both effects disappear with an effective thermalization induced by the Franck-Condon effect in a DQD fabricated in a carbon nanotube with a strong electron-phonon coupling.
In this paper we investigate the spin-current and its shot-noise spectrum in a single-molecule quantum dot coupled with a local phonon mode. We pay special attention on the effect of phonon on the quantum transport property. The spin-polarization dependent current is generated by a rotating magnetic filed applied in the quantum dot. Our results show the remarkable influence of phonon mode on the zero-frequency shot noise. The electron-phonon interaction leads to sideband peaks which are located exactly on the integer number of the phonon frequency and moreover the peak-height is sensitive to t…
We study transport through a double quantum dot system in which each quantum dot is coupled to a phonon mode. Such a system can be realized, e.g., using a suspended carbon nanotube. We find that the interplay between strong electron-phonon coupling and inter-dot tunneling can lead to a negative differential conductance at bias voltages exceeding the phonon frequency. Various transport properties are discussed, and we explain the physics of the occurrence of negative differential conductance in this system.
Theoretical and numerical calculations of two-phonon processes on gated lateral semiconductor quantum dots (QDs) are outlined. A heterostructure made with two laterally coupled QDs, in the presence of an external magnetic field, has been employed in order to study the electron scattering rate due to two-phonon processes. The formalism is based on the acoustic phonon modes via the unscreened deformation potential and the piezoelectric interaction whenever the crystal lattice lacks a center of inversion symmetry. The rates are calculated by using second order perturbation theory. The strong depe…
We calculate the spin relaxation rates in a parabolic InSb quantum dots due to the spin interaction with acoustical phonons. We considered the deformation potential mechanism as the dominant electron-phonon coupling in the Pavlov-Firsov spin-phonon Hamiltonian. By studying suitable choices of magnetic field and lateral dot size, we determine regions where the spin relaxation rates can be practically suppressed. We analyze the behavior of the spin relaxation rates as a function of an external magnetic field and mean quantum dot radius. Effects of the spin admixture due to Dresselhaus contributi…
Spin-polarized transport through a quantum dot strongly coupled to ferromagnetic electrodes with non-collinear magnetic moments is analyzed theoretically in terms of the non-equilibrium Green function formalism. Electrons in the dot are assumed to be coupled to a phonon bath. The influence of electron-phonon coupling on tunnelling current, linear and nonlinear conductance, and on tunnel magnetoresistance is studied in detail. Variation of the main Kondo peaks and phonon satellites with the angle between magnetic moments of the leads is analyzed.
We study theoretically the radiative recombination of excitons in double quantum dots in the presence of carrier-phonon coupling. We show that the phonon-induced pure dephasing effects and transitions between the exciton states strongly modify the spontaneous emission process and make it sensitive to temperature, which may lead to non-monotonic temperature dependence of the time-resolved luminescence. We show also that under specific resonance conditions the biexcitonic interband polarization can be coherently transferred to the excitonic one, leading to an extended life time of the total cohe…
We predict that phonon subband quantization can be detected in the non-linear electron current through double quantum dot qubits embedded into nano-size semiconductor slabs, acting as phonon cavities. For particular values of the dot level splitting $Δ$, piezo-electric or deformation potential scattering is either drastically reduced as compared to the bulk case, or strongly enhanced due to phonon van Hove singularities. By tuning $Δ$ via gate voltages, one can either control dephasing, or strongly increase emission into phonon modes with characteristic angular distributions.
A simple method for describing the evolution of a quantum state of a double quantum dot system interacting simultaneously with the electromagnetic environment and with the lattice modes is developed. It is shown that the joint action of the two reservoirs leads to nontrivial effects in the system dephasing. As an example, the impact of phonon-induced initial dephasing on the radiative decay of delocalized exciton states is discussed.
We consider cotunneling through a quantum dot in the presence of spin-flip processes induced by the coupling to acoustic phonons of the surrounding. An expression for the phonon-assisted cotunneling current is derived by means of a generalized Schrieffer-Wolff transformation. The influence of the spin-phonon coupling on the heating of the dot is considered. The result is evaluated for the case of a parabolic semiconductor quantum dot with Rashba and Dresselhaus spin-orbit coupling and a method for the determination of the spin-phonon relaxation rate is proposed.
We report the inclusion of phonon scattering to our recently established numerical package QmeQ for transport in quantum dot systems. This enables straightforward calculations for a large variety of devices. As examples we show (i) transport in a double-dot structure, where energy relaxation is crucial to match the energy difference between the levels, and (ii) the generation of electrical power by contacting cold electric contacts with quantum dot states, which are subjected to heated phonons.
The contribution of interface phonons to the first order Raman scattering in nanocrystals with non spherical geometry is analyzed. Interface optical phonons in the spheroidal geometry are discussed and the corresponding Frohlich-like electron-phonon interaction is reported in the framework of the dielectric continuum approach. It is shown that the interface phonon modes are strongly dependent on the nanocrystal geometry, particularly on the ellipsoid's semi-axis ratio. The new Raman selection rules have revealed that solely interface phonon modes with even angular momentum are allowed to contr…
Using the Keldysh nonequilibrium Green function technique, we study the current and shot noise spectroscopy of a single molecular quantum dot coupled to a local phonon mode. It is found that in the presence of electron-phonon coupling, in addition to the resonant peak associated with the single level of the dot, satellite peaks with the separation set by the frequency of phonon mode appear in the differential conductance. In the ``single level'' resonant tunneling region, the differential shot noise power exhibit two split peaks. However, only single peaks show up in the ``phonon assisted'' re…
Luminescence spectroscopy experiments were realized for single colloidal quantum dots CdSe/ZnS in a broad temperature range above room temperature in a nitrogen atmosphere. Broadening and shifts of spectra due to the temperature change as well as due to spectral diffusion processes were detected and analyzed. A linear correlation between the positions of maxima and the squared linewidths of the spectra was found. This dependence was explained by a model which takes into account the slow variation of the electron-phonon coupling strength.
Phonon Effects on Population Inversion in Quantum Dots: Resonant, Detuned and Frequency-swept Excitations
该研究探究声学声子对半导体量子点共振、失谐、扫频三类光激发过程的影响，发现声子会阻尼Rabi振荡与扫频激发的粒子数反转，且三种情形下声子影响均随脉冲面积非单调变化。
We calculate the conductance through strongly correlated T-shaped molecular or quantum dot systems under the influence of phonons. The system is modelled by the extended Anderson-Holstein Hamiltonian. The finite-U mean-field slave boson approach is used to study many-body effects. Phonons influence both interference and correlations. Depending on the dot unperturbed energy and the strength of electron-phonon interaction the system is occupied by a different number of electrons which effectively interact with each other repulsively or attractively. This leads together with the interference effe…
We theoretically study the resonant tunneling and Fano resonance in quantum dots with electron-phonon (e-ph) interaction. We examine the bias-voltage ($V$) dependence of the decoherence, using Keldysh Green function method and perturbation with respect to the e-ph interaction. With optical phonons of energy $ω_0$, only the elastic process takes place when $eV<ω_0$, in which electrons emit and absorb phonons virtually. The process suppresses the resonant amplitude. When $eV>ω_0$, the inelastic process is possible which is accompanied by real emission of phonons. It results in the dephasing and …
Spin relaxation in undoped quasi-spherical CdS quantum dots at zero magnetic fields is investigated using time- and polarization-resolved transient absorption measurements. Unlike in previous studies of these systems, the measured signals were corrected for spin-insensitive contributions to the exciton bleaching dynamics, {allowing us to determine} the pure spin-related exciton dynamics. To explain the observed room-temperature spin-relaxation time of several nanoseconds, we propose a novel mechanism based on intralevel exciton transitions with the emission of one LO phonon, the absorption of …
We calculate the longitudinal-acoustic phonon scattering rate for a vertical double quantum dot system with weak lateral confinement and show that a strong modulation of the single-electron excited states lifetime can be induced by an external magnetic or electric field. The results are obtained for typical realistic devices using a Fermi golden rule approach and a three-dimensional description of the electronic quantum states.
Electron-phonon interaction and electronic correlations in transport through electrostatically and tunnel coupled quantum dots
研究双量子点输运中电子-声子耦合与电子关联，采用有限U slave boson方法，发现声子影响近藤效应并导致多种基态，包括极化子共隧穿产生的近藤类态和磁性关联态。
We investigate the influence of the one-dimensional character of the phonon modes in a catalytically grown GaAs nanowire on the absorption spectrum of an embedded quantum dot, focusing on the contribution from the piezoelectric coupling. In general, the reduced dimensionality of the phonons leads to spectral side peaks and a zero-phonon line broadening due to the energetically lowest (acoustic) phonon mode. While the deformation potential predominantly couples to radial modes, the piezoelectric interaction can also couple strongly to modes of axial character, leading to additional absorption f…
The paper discusses two-photon Rabi oscillations between the ground state of a quantum dot and the biexciton state, as well as two-photon oscillations between the two single-exciton states with different circular or linear polarizations. The effect of phonon-induced decoherence on these processes is described and optimal system properties and optical driving conditions for coherent control are identified. It is shown that proper optimalization allows one to control the biexciton system via two-photon transitions with a high fidelity.
We analyse various phonon-assisted mechanisms which contribute to the decoherence of excitonic qubits in quantum dot systems coupled by the Förster-type transfer process. We show the significant loss of coherence accompanied by dissipation due to charge carrier oscillations between qubit states by using a model of one-phonon assisted Förster-type transfer process. We obtain explicit expressions for the relaxation and dephasing times for excitonic qubits interacting with acoustic phonons via both deformation potential and piezoelectric coupling. We compare the decoherence times of the GaAs/AlGa…
It is demonstrated how the exciton and the biexciton state of a quantum dot can be prepared with high fidelity on a picosecond time-scale by driving the dot with a strong laser pulse that is tuned above the exciton resonance for exciton preparation and in resonance with the exciton transition for biexciton preparation. The proposed schemes make use of the phonon-induced relaxation towards photon dressed states in optically driven quantum dots and combine the simplicity of Rabi flopping with the robustness of adiabatic rapid passage schemes. Our protocols allow for an on-demand, fast and almost…
It is shown that in many cases an adequate description of optical spectra of semiconductor quantum dots requires a treatment beyond the commonly used adiabatic approximation. We have developed a theory of phonon-assisted optical transitions in semiconductor quantum dots, which takes into account non-adiabaticity of the exciton-phonon system. Effects of non-adiabaticity lead to a mixing of different exciton and phonon states that provides a key to the understanding of surprisingly high intensities of phonon satellites observed in photoluminescence spectra of quantum dots. A breakdown of the adi…
We present a tunnel spectroscopy study of single PbS Quantum Dots (QDs) as function of temperature and gate voltage. Three distinct signatures of strong electron-phonon coupling are observed in the Electron Tunneling Spectrum (ETS) of these QDs. In the shell-filling regime, the $8\times$ degeneracy of the electronic levels is lifted by the Coulomb interactions and allows the observation of phonon sub-bands that result from the emission of optical phonons. At low bias, a gap is observed in the ETS that cannot be closed with the gate voltage, which is a distinguishing feature of the Franck-Condo…
We study the anisotropic orbital effect in the electric field tunability of the phonon induced spin-flip rate in quantum dots (QDs). Our study shows that anisotropic gate potential enhances the spin-flip rate and reduces the level crossing point to a lower quantum dot radius due to the suppression of the Land$\acute{e}$ g-factor towards bulk crystal. In the range of $10^4-10^6$ V/cm, the electric field tunability of the phonon induced spin-flip rate can be manipulated through strong Dresselhaus spin-orbit coupling. These results might assist the development of a spin based solid state quantum …
We study the second-order polaronic resonance between 2-LO-phonon states and p-shell electron states in a quantum dot. We show that the spectrum in the resonance area can be quantitatively reproduced by a theoretical model using only standard material constants, without any free parameters. We propose also a perturbative approach to the problem based on a quasi-degenerate perturbation theory. This method not only considerably reduces the numerical complexity without considerable loss of accuracy but also gives some insight into the structure and origin of the resonance spectrum.
We report on the impulsive generation of coherent optical phonons in CdTe0.68Se0.32 nanocrystallites embedded in a glass matrix. Pump probe experiments using femtosecond laser pulses were performed by tuning the laser central energy to resonate with the absorption edge of the nanocrystals. We identify two longitudinal optical phonons, one longitudinal acoustic phonon and a fourth mode of a mixed longitudinal-transverse nature. The amplitude of the optical phonons as a function of the laser central energy exhibits a resonance that is well described by a model based on impulsive stimulated Raman…
We estimate the spin relaxation rate due to spin-orbit coupling and acoustic phonon scattering in weakly-confined quantum dots with up to five interacting electrons. The Full Configuration Interaction approach is used to account for the inter-electron repulsion, and Rashba and Dresselhaus spin-orbit couplings are exactly diagonalized. We show that electron-electron interaction strongly affects spin-orbit admixture in the sample. Consequently, relaxation rates strongly depend on the number of carriers confined in the dot. We identify the mechanisms which may lead to improved spin stability in f…
In this paper, a detailed analysis of anisotropic effects on the phonon induced spin relaxation rate in III-V semiconductor quantum dots (QDs) is carried out. We show that the accidental degeneracy due to level crossing between the first and second excited states of opposite electron spin states in both isotropic and anisotropic QDs can be manipulated with the application of externally applied gate potentials. In particular, anisotropic gate potentials enhance the phonon mediated spin-flip rate and reduce the cusp-like structure to lower magnetic fields, in addition to the lower QDs radii in I…
We theoretically propose optical phonon lasing in a double quantum dot (DQD) fabricated on a semiconductor substrate. No additional cavity or resonator is required. An electron in the DQD is found to be coupled to only two longitudinal optical phonon modes that act as a natural cavity. When the energy level spacing in the DQD is tuned to the phonon energy, the electron transfer is accompanied by the emission of the phonon modes. The resulting non-equilibrium motion of electrons and phonons is analyzed by the rate equation approach based on the Born-Markov-Secular approximation. We show that th…
We study the influence of phonon scattering on the single-triplet measurement of two-electron spin states in a double quantum dot doped with two electrons. We point out that at low temperatures phonon-induced relaxation to the ground state suppresses transitions to doubly occupied singlet states which are the source of detectable current fluctuations in this measurement scheme. Thus, for a relatively strong electron-phonon interaction present in the system, the two configurations display the same noise characteristics. In this way, coupling to phonons reduces the distinguishability between the…
We present a theoretical investigation of the optical properties of polaronic excitons in stacked self-assembled quantum dots, which is based on the non-adiabatic approach. A parallelepiped-shaped quantum dot is considered as a model for a self-assembled quantum dot in a stack. The exciton-phonon interaction is taken into account for all phonon modes specific for these quantum dots (bulk-like, half-space and interface phonons). We show that the coupling between stacked quantum dots can lead to a strong enhancement of the optical absorption in the spectral ranges characteristic for phonon satel…
We demonstrate full suppression of dephasing tied to deformation potential coupling of confined electrons to longitunidal acoustic (LA) phonons in optical control experiments on large semiconductor quantum dots (QDs) with emission compatible with the low-dispersion telecommunications band at 1.3~$μ$m. By exploiting the sensitivity of the electron-phonon spectral density to the size and shape of the QD, we demonstrate a four-fold reduction in the threshold pulse area required to enter the decoupled regime for exciton inversion using adiabatic rapid passage (ARP). Our calculations of the quantum…
Recently, longitudinal acoustic phonons have been identified as the main source of the intensity damping observed in Rabi rotation measurements of the ground-state exciton of a single InAs/GaAs quantum dot. Here we report experiments of intensity damped Rabi rotations in the case of detuned laser pulses, the results have implications for the coherent optical control of both excitons and spins using detuned laser pulses.
We study phonon-assisted dephasing in optically excited semiconductor quantum dots within the frameworks of the independent Boson model and optimal control. Using a realistic description for the quantum dot states and the phonon coupling, we demonstrate that such dephasing has a drastic impact on the coherent optical response. We employ optimal control theory to search for control strategies that allow to fight decoherence, and show that appropriate tailoring of laser pulses allows a complete control of the optical excitation despite the phonon dephasing.
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