In a recent paper published in this Journal, Khordad and collaborators [J Low Temp Phys (2018) 190:200] have studied the thermodynamics properties of a GaAs double ring-shaped quantum dot under external magnetic and electric fields. In that meritorious research the energy of system was obtained by solving the Schrödinger equation. The radial equation was mapped into a confluent hypergeometric differential equation and the differential equation associated to $z$ coordinate was mapped into a biconfluent Heun differential equation. In this paper, it is pointed out a misleading treatment on the solution of the biconfluent Heun equation. It is shown that the energy $E_{z}$ can not be labeled with $n_{z}$ and this fact jeopardizes the results of this system. We calculate the partition function with the correct energy spectrum and recalculate the specific heat and entropy as a function of low and high temperatures.
We developed a set of equations to calculate the electronic Green's functions in a T-shaped multi-quantum dot system using the equation of motion method. We model the system using a generalized Anderson Hamiltonian which accounts for {\em finite} intradot on-site Coulomb interaction in all component dots as well as for the interdot electron tunneling between adjacent quantum dots. Our results are obtained within and beyond the Hartree-Fock approximation and provide a path to evaluate all the electronic correlations in the multi-quantum dot system in the Coulomb blockade regime. Both approximat…
Correlation effects on electron transport through a system of T-shaped double-dots are investigated, for which only one of the dots is directly connected to the leads. We evaluate the local density of states and the conductance by means of the non-crossing approximation at finite temperatures as well as the slave-boson mean field approximation at zero temperature. It is found that the dot which is not directly connected to the leads considerably influences the conductance, making its behavior quite different from the case of a single-dot system. In particular, we find a novel phenomenon in the…
Stimulated by recent advances in isolating graphene, we discovered that quantum dot can be trapped in Z-shaped graphene nanoribbon junciton. The topological structure of the junction can confine electronic states completely. By varying junction length, we can alter the spatial confinement and the number of discrete levels within the junction. In addition, quantum dot can be realized regardless of substrate induced static disorder or irregular edges of the junction. This device can be used to easily design quantum dot devices. This platform can also be used to design zero-dimensional functional…
We have measured the low-temperature transport properties of a T-shaped quantum dot. Replicated oscillations superimposed on one-dimensional conductance steps are observed. These structures are consistent with electron phase-coherent length resonance effects in the ballistic regime. Using a simple model, we suggest that both one-dimensional and two-dimensional electron-electron scattering gives rise to electron phase-breaking in our system.
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 investigate the Aharonov-Bohm (AB) effect for the double quantum dots in the Kondo regime using the slave-boson mean-field approximation. In contrast to the non-interacting case, where the AB oscillation generally has the period of 4$π$ when the two-subring structure is formed via the interdot tunneling $t_c$, we find that the AB oscillation has the period of 2$π$ in the Kondo regime. Such effects appear for the double quantum dots close to the T-shaped geometry even in the charge-fluctuation regime. These results follow from the fact that the Kondo resonance is always fixed to the Fermi le…
The bound states of a particle in a lens-shaped quantum dot with finite confinement potential are obtained in the envelope function approximation. The quantum dot has circular base with radius $a$ and maximum cap height $b$, and the effective mass of the particle is considered different inside and outside the dot. A 2D Fourier expansion is used in a semi-sphere domain with infinite walls which contains the geometry of the original potential. Electron energies for different values of lens deformation $b/a$, lens radius $a$ and barrier height $V_o$ are calculated. In the very high confinement po…
In this work, the effect of size and wetting layer on subband electronic envelop functions, eigenenergies, linear and nonlinear absorption coefficients and refractive indices of a dome-shaped InAs/GaAs quantum dot were investigated. In our model, a dome of InAs quantum dot with its wetting layer embedded in a GaAs matrix was considered. A finite height barrier potential at the InAs/GaAs interface was assumed. To calculate envelop functions and eigenenergies, the effective one electronic band Hamiltonian and electron effective mass approximation were used. The linear and nonlinear optical prope…
Experimental realization of graphene-based stadium-shaped quantum dots (QDs) have been few and incompatible with scanned probe microscopy. Yet, direct visualization of electronic states within these QDs is crucial for determining the existence of quantum chaos in these systems. We report the fabrication and characterization of electrostatically defined stadium-shaped QDs in heterostructure devices composed of monolayer graphene (MLG) and bilayer graphene (BLG). To realize a stadium-shaped QD, we utilized the tip of a scanning tunneling microscope to charge defects in a supporting hexagonal bor…
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…
Real-time detection of single electron tunneling through a T-shaped double quantum dot is simulated, based on a Monte Carlo scheme. The double dot is embedded in a dissipative environment and the presence of electrons on the double dot is detected with a nearby quantum point contact. We demonstrate directly the bunching behavior in electron transport, which leads eventually to a super-Poissonian noise. Particularly, in the context of full counting statistics, we investigate the essential difference between the dephasing mechanisms induced by the quantum point contact detection and the coupling…
We theoretically study the transport properties in the T-shaped double-quantum-dot structure, by introducing the Majorana bound state (MBS) to couple to the dot in the main channel. It is found that the side-coupled dot governs the effect of the MBS on the transport behavior. When its level is consistent with the energy zero point, the MBS contributes little to the conductance spectrum. Otherwise, the linear conductance exhibits notable changes according to the inter-MBS coupling manners. In the case of Majorana zero mode, the linear conductance value keeps equal to $e^2\over 2h$ when the leve…
We theoretically investigate the absorption and emission of light carrying orbital angular momentum (twisted-light) by quasi-two-dimensional (disc-shaped) quantum dots in the presence of a static magnetic field. We calculate the transition matrix element for the light-matter interaction and use it to explore different scenarios, depending on the initial and final state of the electron undergoing the optically-induced transition. We make explicit the selection rule for the conservation of the z-projection of the orbital angular momentum. For a realistic set of parameters (quantum dots size, bea…
Confined excitonic complexes in two dimensions, consisting of N_e electrons and N_h holes, are studied by means of Bethe-Goldstone equations. Systems with up to twelve pairs, and asymmetric configurations with N_e \ne N_h are considered. The weak confinement regime gives indication of weak binding or even unbinding in the triexciton and the four-exciton system, and binding in the higher complexes.
We investigate the conductance of an undoped graphene sheet with two metallic contacts and an electrostatically gated island (quantum dot) between the contacts. Our analysis is based on the Matrix Green Function formalism, which was recently adapted to graphene by Titov {\em et al.} [Phys.\ Rev.\ Lett.\ {\bf 104}, 076802 (2010)]. We find pronounced differences between the case of a stadium-shaped dot (which has chaotic classical dynamics) and a disc-shaped dot (which has integrable classical dynamics) in the limit that the dot size is small in comparison to the distance between the contacts. I…
We study the spin-resolved transport properties of T-shaped double quantum dots coupled to ferromagnetic leads. Using the numerical renormalization group method, we calculate the linear conductance and the spin polarization of the current for various model parameters and at different temperatures. We show that an effective exchange field due to the presence of ferromagnets results in different conditions for Fano destructive interference in each spin channel. This spin dependence of the Fano effect leads to perfect spin polarization, the sign of which can be changed by tuning the dots' levels.…
We investigate the thermoelectric properties of a T-shaped double quantum dot system described by a generalized Anderson Hamiltonian. The system's electrical conduction (G) and the fundamental thermoelectric parameters such as the Seebeck coefficient ($S$) and the thermal conductivity ($κ$), along with the system's thermoelectric figure of merit (ZT) are numerically estimated based on a Green's function formalism that includes contributions up to the Hartree-Fock level. Our results account for finite onsite Coulomb interaction terms in both component quantum dots and discuss various ways leadi…
The quasi-bound states of a superconducting quantum dot that is weakly coupled to a normal metal appear as resonances in the Andreev reflection probability, measured via the differential conductance. We study the evolution of these Andreev resonances when an external parameter (such as magnetic field or gate voltage) is varied, using a random-matrix model for the $N\times N$ scattering matrix. We contrast the two ensembles with broken time-reversal symmetry, in the presence or absence of spin-rotation symmetry (class C or D). The poles of the scattering matrix in the complex plane, encoding th…
The phase and thermal driven transport properties of the T-shaped uncorrelated double quantum dot Josephson junction are analyzed by using Keldysh non-equilibrium Green's function equation of motion technique. In this setup, we have shown that the side-attached quantum dot provides an additional route for electron transmission which is affecting the transport properties by adjusting the interdot hopping between the main dot and the side dot. We began with investigating the impact of interdot hopping on Andreev bound states and Josephson supercurrent. When a small thermal bias is applied across…
We theoretically investigate the thermoelectric and spin thermoelectric properties of a T-shaped double quantum dot strongly coupled to two ferromagnetic leads, focusing on transport regime where the system exhibits the two-stage Kondo effect. We study the dependence of the (spin) Seebeck coefficient, the corresponding power factor and the figure of merit on temperature, leads' spin polarization and dot level position. We show that the thermal conductance fulfills a modified Wiedemann-Franz law. We also demonstrate that the spin thermopower is enhanced at temperatures corresponding to the seco…
We investigate transport properties through a crossbar-shaped structure formed by a quantum dot (QD) coupled to two normal leads and embedded between two one-dimensional topological superconductors (TSCs). Each TSC hosts Majorana bound states (MBSs) at its ends, which can interact between them with an effective coupling strength. We find a signature of bound states in continuum (BIC) in the MBSs spectral function. By allowing finite inter MBSs coupling, BICs splitting is observed and shows projection in transmission for asymmetric coupling case as cuasi-BICs. As a consequence, we also show tha…
Electron transport through the T-shaped quantum-dot (QD) structure is theoretically investigated, by considering a Majorana zero mode coupled to the terminal QD. It is found that in the double-QD case, the presence of the Majorana zero mode can efficiently dissolve the antiresonance point in the conductance spectrum and induce a conductance peak to appear at the same energy position whose value is equal to $e^2/2h$. This antiresonance-resonance change will be suitable to detect the Majorana bound states. Next in the multi-QD case, we observe that in the zero-bias limit, the conductances are al…
In this paper, optical and electronic properties of diamond shaped graphene quantum dots (DQDs) have been studied by employing large-scale electron-correlated calculations. The computations have been performed using the π-electron Pariser-Parr-Pople model Hamiltonian, which incorporates long-range Coulomb interactions. The influence of electron-correlation effects on the ground and excited states has been included by means of the configuration-interaction approach, used at various levels. Our calculations have revealed that the absorption spectra are red-shifted with the increasing sizes of qu…
Based on Keldysh non-equilibrium Green function method, we have investigated spin current production in a hybrid T-shaped device, consisting of a central quantum dot connected to the leads and a side dot which only couples to the central dot. The topology of this structure allows for quantum interference of the different paths that go across the device, yielding Fano resonances in the spin dependent transport properties. Correlation effects are taken into account at the central dot and handled within a mean field approximation. Its interplay with the Fano effect is analyzed in the strong coupl…
In the present work, we investigate the thermoelectric properties of a T-shaped double quantum dot system coupled to two metallic leads incorporating the intra-dot Coulomb interaction. We explore the role of the interference effects and Coulomb blockade on the thermoelectric efficiency of the system in the linear and nonlinear regimes. We studied as well the effect of a Van-Hove singularity of the leads density of states (DOS) at the neighborhood of the Fermi energy, a situation that can be obtained using a carbon nanotube, a graphene nano-ribbon or other contacts with one-dimensional properti…
We theoretically investigate the Kondo effect of a T-shaped triple-quantum-dot structure, by means of the numerical renormalization group method. It is found that at the point of electron-hole symmetry, the system's entropy has opportunities to exhibit three kinds of transition processes for different interdot couplings, with the decrease of temperature. This leads to the different pictures of the Kondo physics, including the three-stage Kondo effect. Next when the electron-hole symmetry is broken or the structural parameters are changed, the Kondo resonance can also be observed in the conduct…
We examine the transport properties of a double quantum dot system coupled to a topological superconducting nanowire hosting Majorana quasiparticles at its ends, with the central quantum dot attached to the left and right leads. We focus on the behavior of the local density of states and the linear conductance, calculated with the aid of the numerical renormalization group method, to describe the influence of the Majorana coupling on the low-temperature transport properties induced by the Kondo correlations. In particular, we show that the presence of Majorana quasiparticles in the system affe…
Motivated by recent advances in fabricating graphene nanostructures, we find that an electron can be trapped in Z-shaped graphene nanoconstriction with zigzag edges. The central section of the constriction operates as a single-level quantum dot, as the current flow towards the adjunct sections (rotated by 60 degree) is strongly suppressed due to mismatched valley polarization, although each section in isolation shows maximal quantum value of the conductance $G_0=2e^2/h$. We further show, that the trapping mechanism is insensitive to the details of constriction geometry, except from the case wh…
We propose to continuously monitor a charge qubit by utilizing a T-shaped double quantum dot detector, in which the qubit and double dot are arranged in such a unique way that the detector turns out to be particularly susceptible to the charge states of the qubit. Special attention is paid to the regime where acquisition of qubit information and backaction upon the measured system exhibit nontrivial correlation. The intrinsic dynamics of the qubit gives rise to dynamical blockade of tunneling events through the detector, resulting in a super-Poissonian noise. However, such a pronounced enhance…
We examine the influence of the superconducting proximity effect on the transport properties of a T-shaped double quantum dot strongly coupled to two normal, nonmagnetic or ferromagnetic leads. We show that the two-stage Kondo screening may be suppressed or enhanced by the presence of pairing correlations, depending on the specific geometric arrangement of the device. We explain our results by invoking effective decrease of Coulomb interactions by proximity effect and find qualitatively correct description in many cases, although spin-filtering effect stemming from spin-dependent Fano-Kondo in…
We study the effects of intraband relaxation processes on optical manipulation protocols for sp biexcitons hosted by CdTe disk-shaped quantum dots. The many-body states are calculated within the configuration interaction method starting from single-particle states given by the kp theory. The time-dependent occupations of relevant many-body states are extracted from the von Neumann-Lindblad equation for the density operator. We mainly investigate the generation of sp biexcitons with two pulses of different polarizations sigma_{+} and sigma_{-}. The fast hole relaxation processes prevent a high-…
We use quantum optimal control theory algorithms to design external electric fields that drive the coupled spin and orbital dynamics of an electron in a double quantum dot, subject to the spin-orbit interaction and Zeeman magnetic fields. We obtain time-profiles of multi-frequency electric pulses which increase the rate of spin-flip transitions by several orders of magnitude in comparison with monochromatic fields, where the spin Rabi oscillations were predicted to be very slow. This precise, with the accuracy higher than $10^{-4}$, and fast, at the timescale of the order of 0.1 ns, simultaneo…
This letter is devoted to the optimization of the Cooper pair splitting efficiency in a Y-shaped junction. The latter consists of two quantum dots, one superconducting and two normal leads. We tailor the bias in the two normal leads such that the Cooper pairs leaving the superconductor are split up resulting in entangled electrons, one on each quantum dot. We are able to achieve a splitting efficiency of more than 99% which is significantly better than the efficiencies obtained in experiments so far.
We study Rabi rotations arising in intensity-dependent photon echoes from an ensemble of self-assembled InGaAs quantum dots. To achieve a uniform distribution of intensities within the excited ensemble, we introduce flattop intensity profiles of picosecond laser pulses. This allows us to overcome the damping of Rabi rotations imposed by the spatial inhomogeneity of Rabi frequencies by a Gaussian laser profile. Using photon echo polarimetry, we distinguish between the coherent optical responses from exciton and trion ensembles. Here, we demonstrate that a photo-induced charging of the quantum d…
We study the influence of a magnetic flux tube on the possibility to electrostatically confine electrons in a graphene quantum dot. Without magnetic flux tube, the graphene pseudospin is responsible for a quantization of the total angular momentum to half-integer values. On the other hand, with a flux tube containing half a flux quantum, the Aharonov-Bohm phase and Berry phase precisely cancel, and we find a state at zero angular momentum that cannot be confined electrostatically. In this case, true bound states only exist in regular geometries for which states without zero-angular-momentum co…
In quasi-1D $π$-conjugated polymers such as \emph{trans}-polyacetylene and polyenes, electron correlation effects determine the "reversed" excited state ordering in which the lowest two-photon $2A_{g}$ state lies below the lowest one-photon $1B_{u}$ state. In this work, we present conclusive theoretical evidence of reversed excited state ordering in fairly 2D $π$-conjugated systems, namely, diamond-shaped graphene quantum dots (DQDs). Our electron correlated calculations show that DQDs begin to exhibit reversed excited ordering with increasing size, in disagreement with independent-particle pi…
In the present work we theoretically study thermoelectric transport and heat transfer in a junction including a $T$-shaped double quantum dot coupled to nonmagnetic electrodes and supplemented with a third dot in a parallel configuration. We focus on the combined effect of Coulomb interactions and quantum interference occurring in the $T$-shaped portion of the considered triple quantum dot on the thermoelectric electron transport. The transport through the system is studied within the Coulomb blockade regime in the limit of strong intra-dot interactions between electrons beyond the linear resp…
The transport behavior of a double quantum dot side-attached to a topological superconducting wire hosting Majorana zero-energy modes is studied theoretically in the strong correlation regime. It is shown that Majorana modes can leak to the whole nanostructure, giving rise to a subtle interplay between the two-stage Kondo screening and the half-fermionic nature of Majorana quasiparticles. In particular, the coupling to the topological wire is found to reduce the effective exchange interaction between the two quantum dots in the absence of normal leads. Interestingly, it also results in an enha…
In this work the intersubband electronic properties of two laterally coupled dome-shaped InAs/GaAs quantum dots were investigated. The envelope functions and eigenenergies were calculated as function of distance between the dots. The coupling between the dots was studied using transition lifetime between the dots. The results showed that in close distances (smaller than 3 nm) the quantum dots are coupled and by increasing the distance transition lifetime fall down drastically and the dots become uncoupled.
We analyze the zero temperature conductance of a parallel T-shaped double quantum dot system. We present an analytical expression for the conductance of the system in terms of the total number of electrons in both quantum dots. Our results confirm that the system's conductance is strongly influenced by the dot which is not directly connected to the leads. We discuss our results in connection with similar results reported in the literature.
We use the Bloch-Redfield-Wangsness theory to calculate the effects of acoustic phonons in coherent control experiments, where quantum-dot excitons are driven by shaped laser pulses. This theory yields a generalized Lindblad equation for the density operator of the dot, with time-dependent damping and decoherence due to phonon transitions between the instantaneous dressed states. It captures similar physics to the form recently applied to Rabi oscillation experiments [A. J. Ramsay et al., Phys. Rev. Lett. 104, 017402 (2010)], but guarantees positivity of the density operator. At sufficiently l…
Motivated by a proposal to create an optical helix-shaped waveguides for cold atoms and molecules, we discuss local perturbations which can create bound states in such a setting. This is known about a local slowdown of the twist; we show that a similar effect can result from a local tube protrusion or a change of the helix radius in correlation with its pitch angle.
Confinement in two-dimensional transition metal dichalcogenides is an attractive platform for trapping single charge and spins for quantum information processing. Here, we present low temperature electron transport through etched 50-70nm MoS2 nanoribbons showing current oscillations as a function of gate voltage. On further investigations current through the device forms diamond shaped domains as a function of source-drain and gate voltage. We associate these current oscillations and diamond shaped current domains with Coulomb blockade due to single electron tunneling through a quantum dot for…
We theoretically examine the capacitive coupling between two quantum dot hybrid qubits, each consisting of three electrons in a double quantum dot, as a function of the energy detuning of the double dot potentials. We show that a shaped detuning pulse can produce a two-qubit maximally entangling operation in $\sim$50ns without having to simultaneously change tunnel couplings. Simulations of the entangling operation in the presence of experimentally realistic charge noise yield two-qubit fidelities over 90%.
Control of single photon wave-packets is an important resource for developing hybrid quantum systems which are composed of different physical systems interacting via photons. Here we extend this control to triggered photons emitted by a quantum dot, temporally shaping single photon wave-packets on timescales fast compared to their radiative decay by electro-optic modulation. In particular, telecommunications-band single photons resulting from the recombination of an exciton in a quantum dot with exponentially decaying wave-packets are synchronously modulated to create Gaussian-shaped single ph…
We report transport data obtained for a double-gated bilayer graphene quantum dot. In Coulomb blockade measurements, the gate dielectric Cytop(TM) is found to provide remarkable electronic stability even at cryogenic temperatures. Moreover, we demonstrate gate manipulation with square shaped voltage pulses at frequencies up to 100 MHz and show that the signal amplitude is not affected by the presence of the capacitively coupled back gate.
The spin-polarized transport through a coherent strongly coupled double quantum dot (DQD) system is analyzed theoretically in the sequential and cotunneling regimes. Using the real-time diagrammatic technique, we analyze the current, differential conductance, shot noise and tunnel magnetoresistance (TMR) as a function of both the bias and gate voltages for double quantum dots coupled in series, in parallel as well as for T-shaped systems. For DQDs coupled in series, we find a strong dependence of the TMR on the number of electrons occupying the double dot, and super-Poissonian shot noise in th…
The Fano-Kondo effect in zero-bias conductance is studied based on a theoretical model for the T-shaped quantum dot by the finite temperature density matrix renormalization group method. The modification of the two Fano line shapes at much higher temperatures than the Kondo temperature is also investigated by the effective Fano parameter estimated as a fitting parameter.
We report temperature-dependent photoluminescence (PL) studies and PL relaxation dynamics for uncoated and silver-coated CdS quantum dots (QDs). Room-temperature photoluminescence studies indicate that the presence of silver coating on CdS QD samples enhances the blue luminescence corresponding to the band-to-band transitions by a factor of ten compared to the uncoated samples. Furthermore, the decay time measurements using Time Correlated Single Photon Counting technique demonstrate Förster resonance energy transfer (FRET) between silver-shell and CdS-core in silver-coated CdS QD samples. A d…
Properly regularized second-order degenerate perturbation theory is applied to compute the contribution of higher Landau levels to the low-energy spectrum of interacting electrons in a disk-shaped quantum dot. At ``filling factor'' near 1/2, this contribution proves to be larger than energy differences between states with different spin polarizations. After checking convergence of the method in small systems, we show results for a 12-electron quantum dot, a system which is hardly tractable by means of exact diagonalization techniques.
We study the transient heat generation in a quantum dot system driven by a step-like or a square-shaped pulse bias. We find that a periodically oscillating heat generation arises after adding the sudden bias. One particularly surprising result is that there exists a heat absorption from the zero-temperature phonon subsystem. Thus the phonon population in non-equilibrium can be less than that of the equilibrium electron-phonon system. In addition, we also ascertain the optimal conditions for the operation of a quantum dot with the minimum heat generation.
Spin-$\frac{1}{2}$ $^{119}$Sn nuclei in a silicon semiconductor could make excellent qubits. Nuclear spins in silicon are known to have long coherence times. Tin is isoelectronic with silicon, so we expect electrons can easily shuttle from one Sn atom to another to propagate quantum information via a hyperfine interaction that we predict, from all-electron linearized augmented plane wave density functional theory calculations, to be roughly ten times larger than intrinsic $^{29}$Si. A hyperfine-induced electro-nuclear controlled-phase (e-n-CPhase) gate operation, generated (up to local rotatio…
We engineer a system of two strongly confined quantum dots to gain reproducible electrostatic control of the spin at zero magnetic field. Coupling the dots in a tight ring-shaped potential with two tunnel barriers, we demonstrate that an electric field can switch the electron ground state between a singlet and a triplet configuration. Comparing our experimental co-tunneling spectroscopy data to a full many-body treatment of interacting electrons in a double-barrier quantum ring, we find excellent agreement in the evolution of many-body states with electric and magnetic fields. The calculations…
In this letter, we propose a new model to determine the recombination oscillator strength of trions and biexcitons for bound and unbound cases in the effective mass approximation. The validity of our model has been confirmed by the radiative lifetime of the trion and biexciton in a spherical quantum dot. The results show that the model works sufficient accuracy in comparison with results of more complex methods such as quantum monte carlo techniques and atomistic calculations.
We report on the spectroscopic investigation of quantum dot - micropillar cavities with unprecedented quality factors. We observe a pronounced dependency of the quality factor on the measurement scheme, and find that significantly larger quality factors can be extracted in photoreflectance compared to photoluminescence measurements. While the photoluminescence spectra of the microcavity resonances feature a Lorentzian lineshape and Q-factors up to 184,000, the reflectance spectra have a Fano-shaped asymmetry and feature significantly higher Q-factors in excess of 250,000 resulting from a full …
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…
The excitation of semiconductor quantum dots often involves an attached wetting layer with delocalized single-particle energy eigenstates. These wetting-layer states are usually approximated by (orthogonalized) plane waves. We show that this approach is too crude. Even for a simple model based on the effective-mass approximation and containing one or a few lens-shaped quantum dots in a rectangular wetting layer, the wetting-layer states typically show a substantially irregular and complex morphology. To quantify this complexity we use concepts from the field of quantum chaos such as spectral a…
