Optical Absorptions of Impurity-Bound Polaron in a GaAs Quantum Dot with Parabolic Potential

The linear and nonlinear optical properties considering polaron and Coulomb impurity effect in a GaAs parabolic quantum dot are investigated theoretically. Calculations have been performed by using the compact density-matrix approach and the Lee-Low-Pines-Huybrecht variational technique for all electron–LO–phonon coupling strengths. The dependence of the optical absorption coefficients on the incident photon energy, the Coulomb potential and incident optical intensity is also studied.     

Temperature Dependence of Polaronic Correction to the Ground State Energy in a GaAs Parabolic Quantum Dot

Within the framework of second-order Rayleigh-Schrodinger perturbation theory (RSPT), the polaronic corrections to the ground state (GS) energy of an electron in both two-dimensional (2D) and three-dimensional (3D) parabolic quantum dots (QDs) are presented at finite temperature. We apply our calculations to GaAs. It is found that the polaronic corrections to the GS energy of an electron in both 2D and 3D QDs increase with temperature increasing and size of the QD decreasing. Furthermore, this trend is much more pronounced with dimensionality decreasing.     

The Rashba Effect of Polaron in a Parabolic Quantum Dot

The condition of electric-LO phonon strong coupling in a parabolic quantum dot (QD) is studied in detail. We obtain the polaron ground state energy by the variational method of Pekar, considering the influence of the Rashba SO interaction. The relations on the polaron ground state energy with the parallel confinement length, the electron-LO phonon coupling constant and the perpendicular confinement length are derived for a parabolic quantum dot.     

The Rashba Effect on the Bound Polaron in a Parabolic Quantum Dot

The bound polaron ground state energy is calculated by the variational method of Pekar considering the influence of the Rashba SO interaction on the condition of electric?CLO phonon strong coupling in a parabolic quantum dot (QD). The relations on the bound polaron ground state energy with the parallel confinement length, the electron?CLO phonon coupling constant, the perpendicular confinement length and the Coulomb binding parameter are derived for a parabolic quantum dot.     

Temperature and Impurity Effects of the Polaron in an Anisotropic Quantum Dot

We study the temperature and impurity effects of the ground state energy and the ground state binding energy in an anisotropic quantum dot by using the linear combination operator method. We also discuss the relations of the vibrational frequency and the mean number phonons varying with the Coulomb bound potential at different electron-phonon coupling strength. It is found that the ground state energy and the ground state binding energy will increase with increasing temperature. The ground state energy is a decreasing function of the Coulomb bound potential, whereas the ground state binding energy is an increasing one of it.     

The Properties of the Polaron Ground State in a Parabolic Quantum Dot and Ring

The polaron ground state energy is obtained by using variational method of Pekar type on the condition of electric-LO phonon strong coupling in a quantum dot and ring. The relations of the polaron ground state energy on the inner confinement strength, the outer confinement strength, the inner and outer radius of quantum dot and ring are derived.     

Temperature Dependence of Strong-Coupled Polaron in a Triangular Potential Quantum Dot

The effect of temperature on the ground-state energy of polaron was obtained with strong electron-LO-phonon coupling by using a variational method of the Pekar type in triangular potential quantum dot (QD). The ground-state energy was expressed as functions of the confinement length of QD, the coupling strength, the polar angle and the temperature. It is found that the ground-state energy decreases with increasing the confinement length of QD and the electron-phonon coupling strength and increases with enhancing the temperature.     

The Temperature Effects on the Parabolic Quantum Dot Qubit in the Electric Field

The temperature effects on the parabolic quantum dot qubit in the electric field have been studied under the condition of electric-LO-phonon strong coupling using the variational method of Pekar type. The numerical results lead us to formulate the derivative relationships of the oscillation period of the electron in the superposition state of the ground state and the first-excited state with the electric field, the electron-LO-phonon coupling constant and the confinement length at different temperatures, respectively.     

Temperature Effect on Effective Mass of the Polaron in an Asymmetric Quantum Dot

We investigate the properties of the polaron in an asymmetric quantum dot by using an improved linear combination operator method. The relations between the mean number of phonons, the effective mass and the temperature are derived. It is found that the mean number of phonons and the effective mass are increasing functions of the temperature.     

Influences of the Temperature on the Parabolic Quantum Dot Qubit in the Magnetic Field

Using the variational method of the Pekar type, we study the influences of the temperature on the parabolic quantum dot qubit in the magnetic field under the condition of electric–LO-phonon strong coupling. Then we derive the numerical results and formulate the derivative relationships of the oscillation period of the electron in the superposition state of the ground state and the first-excited state with the magnetic field, the electron–LO-phonon coupling constant and the confinement length at different temperatures, respectively.     

Effects of Magnetic Field on the Coherence Time of a Parabolic Quantum Dot Qubit

We obtain the eigenenergies and eigenfunctions (EE) of the ground and first excited states of an electron strongly coupled to LO-phonon in a parabolic quantum dot. The effect of an applied magnetic field is considered by using variational method of Pekar type. This system may be regarded as a two-level qubit. Spontaneous phonon emission arouses the qubit’s decoherence. Relations between the coherence time (CT) and the magnetic field, the effective confinement length (ECL) and the polaron radius (PR) are numerically calculated. It is found that the CT is an increasing function of the ECL, whereas it is a decreasing one of the cyclotron frequency and PR. We can extend the CT by changing these parameters in the correlated quantum functional devices.     

Rashba Effect on the Bound Polaron in an Asymmetric Quantum Dot

By using LLP variational method, the Rashba effect on the bound polaron in an asymmetric quantum dot is investigated and the expression of the bound polaron ground state energy is derived. Considering different Coulomb bound potentials, we discuss the relations between the ground state energy and the electron–phonon coupling strength, the wave vector, the transverse effective confinement length and the longitudsinal effective confinement length, respectively. The results show that the ground state energy is a decreasing function of the Coulomb bound potential, the electron–phonon coupling strength, the transverse effective confinement length and the longitudinal effective confinement length. On the contrary, it is an increasing function of the wave vector. Due to the Rashba effect, the ground state energy splits into two branches.     

The Ground-State Lifetime of Polaron in Disk-Shape Quantum Dot

The ground-state lifetime of polaron in disk-shape quantum dot (QD) has been investigated by using the variational method of Pekar type. Quantum transition is occurred in the quantum system due to the electron-phonon interaction and the influence of temperature. That is the polaron transit from the ground-state to the first-excited state after absorbing a LO-phonon and it causes the changing of the polaron lifetime. The result shows that the ground-state lifetime increases with the increasing of the ground-state energy and decreases with the increasing of the electron-LO-phonon coupling strength, the temperature and the confinement length. We also see that the influence of the longitudinal confinement length on the lifetime is larger than the transverse confinement length.     

Rashba Effect on the Effective Mass of the Polaron in a Parabolic Quantum Well

We investigate the influence of the Rashba effect on the properties of the polaron in a parabolic quantum well within the improved linear combination operator method. We discuss the relations among the polaron effective mass ratio with the vibrational frequency, the electron–phonon coupling strength, the velocity of the polaron and the Rashba parameter, respectively. Due to Rashba effect, the effective mass ratio occurs splitting. The effective mass ratio is an increase function of the vibrational frequency and the coupling strength. The change tendencies of the spin-up splitting effective mass ratio and the spin-down splitting effective mass ratio with the velocity and the Rashba parameter are opposite.     

The Effect of Magnetic on the Properties of a Parabolic Quantum Dot Qubit

On the condition of electric-LO phonon strong coupling in a parabolic quantum dot, we obtained the eigen energies and the eigenfunctions of the ground state and the first excited state by using the variational method of Pekar type. This system in a quantum dot may be employed as a two-level quantum system qubit. When the electron is in the superposition state of the ground state and the first excited state, we obtained the space-time evolution of the electron density. The relations on the cyclotron frequency with the electron probability density and the period of oscillation are derived in a parabolic quantum dot.     

Temperature and Excitation Dependence of Photoluminescence Spectra of InAs/GaAs Quantum Dot Heterostructures

In this study we investigated the effects that the carrier dynamics have on the temperature- and excitation-intensity- dependent photoluminescence (PL) spectra of a self-assembled quantum dot heterostructure. A rate equation model is proposed to take into account the dot size distribution, the random population of density of states, state filling effects, and the important carrier transfer mechanisms for the quantum dot system, including carrier capture, relaxation, thermal emission, and retrapping. This model reproduces the PL spectra quite well. Our quantitative calculations of the behavior of the thermal emitting carriers under various incident power intensities within the temperature range 15 K-240 K explain the carrier transfer process quite reasonably for the quantum dot system. In addition, we discuss the thermal redistribution and state filling effects in detail in our analysis of the dependence of the PL spectra on the temperature and excitation power intensity applied to the sample. Index     

Electric Field Effect on State Energies and Transition Frequency of a Strong-Coupling Polaron in an Asymmetric Quantum Dot

We study the ground and the first excited states’ energies and the corresponding transition frequency of a strong-coupling polaron in an asymmetric quantum dot (AQD). The effects of the electric field, the transverse and the longitudinal effective confinement lengths and the electron-phonon coupling strength are taken into account by using a variational method of the Pekar type. It is found that the ground and the first excited states’ energies and the transition frequency are decreasing functions of the electric field. They will increase rapidly with decreasing the transverse and longitudinal effective confinement lengths. The transition frequency is an increasing function of the electron-phonon coupling strength, whereas the energies are decreasing ones of it.     

Temperature Effect on Magnetopolaronic Vibrational Frequency in an Anisotropic Quantum Dot

We study the temperature effects of the vibrational frequency, the ground state energy and the ground state binding energy of the strong-coupling magnetopolaron in an anisotropic quantum dot. The vibrational frequency, the ground state energy and the ground state binding energy are expressed as functions of the temperature, the cyclotron frequency of a magnetic field and the electron-phonon coupling strength by using linear combination operator and unitary transformation methods. It is found that these quantities will increase with increasing temperature and cyclotron frequency of a magnetic field. The vibrational frequency and the ground state binding energy are increasing functions of the electron-phonon coupling strength, whereas the ground state energy is an decreasing one of it.     

Influence of Magnetic Field and LO Phonon Effects on the Spin Polarization State Energy of Strong-Coupling Bipolaron in a Quantum Dot

On the basis of Lee–Low–Pines unitary transformation, the influence of magnetic field and LO phonon effects on the energy of spin polarization states of strong-coupling bipolarons in a quantum dot (QD) is studied by using the variational method of Pekar type. The variations of the ground state energy $E_0$ and the first excited state the energy $E_1$ of bipolarons in a two-dimensional QD with the confinement strength of QDs $\omega _0$ , dielectric constant ratio $\eta $ , electron–phonon coupling strength $\alpha $ and cyclotron resonance frequency of the magnetic field $\omega _{c}$ are derived when the influence of the spin and external magnetic field is taken into account. The results show that both energies of the ground and first excited states ( $E_0$ and $E_1)$ consist of four parts: the single-particle energy of electrons $E_\mathrm{e}$ , Coulomb interaction energy between two electrons $E_\mathrm{c}$ , interaction energy between the electron spin and magnetic field $E_\mathrm{S}$ and interaction energy between the electron and phonon $E_{\mathrm{e-ph}}$ ; the energy level of the first excited state $E_1$ splits into two lines as $E_1^{(1+1)}$ and $E_1^{(1-1)}$ due to the interaction between the single-particle “orbital” motion and magnetic field, and each energy level of the ground and first excited states splits into three “fine structures” caused by the interaction between the electron spin and magnetic field; the value of $E_{\mathrm{e-ph}}$ is always less than zero and its absolute value increases with increasing $\omega _0$ , $\alpha $ and $\omega _c$ ; the effect of the interaction between the electron and phonon is favorable to forming the binding bipolaron, but the existence of the confinement potential and Coulomb repulsive energy between electrons goes against that; the bipolaron with energy $E_1^{(1-1)}$ is easier and more stable in the binding state than that with $E_1^{(1+1)}$ .