Pressure and Temperature Effects on the Magnetic Properties of Donor Impurities in a GaAs/AlGaAs Quantum Heterostructure Subjected to a Magnetic Field

The exact diagonalization method has been used to solve the effective-mass Hamiltonian of a single electron confined parabolically in the GaAs/AlGaAs quantum heterostructure, in the presence of a donor impurity and under the effect of an applied uniform magnetic field. The donor impurity is located at distance (d) along the growth direction which is perpendicular to the motion of the electron in a two-dimensional heterostructure layer. We have investigated the dependence of the magnetization (M) and magnetic susceptibility (χ) of a GaAs/AlGaAs quantum heterostructure nanomaterial on the magnetic field strength (ω_c), confining frequency (ω_o), donor impurity position (d), pressure (P) and temperature (T). Keywords: Exact diagonalization, Donor impurity, Magnetic field, Magnetization, Magnetic susceptibility, Pressure and temperature.

One-particle spectral densities and phase diagrams of one-dimensional proton conductors

The equilibrium states of one-dimensional proton conductors in the systems with hydrogen bonds are investigated. Our extended hard-core boson lattice model includes short-range interactions between hydrogen ions, their transfer along the hydrogen bonds with two-minima local anharmonic potential, as well as their inter-bond hopping, and the modulating field is taken into account. The exact diagonalization method for finite one-dimensional system with periodic boundary conditions is used. The existence of various phases of the system at T = 0, depending on the values of short-range interactions between particles and the modulating field strength, is established by analyzing the character of the obtained frequency dependence of one-particle spectral density; the phase diagrams are built.

Maximally Localized Dynamical Quantum Embedding for Solving Many-Body Correlated Systems

We present a quantum embedding methodology to resolve the Anderson impurity model in the context of dynamical mean-field theory, based on an extended exact diagonalization method. Our method provides a maximally localized quantum impurity model, where the non-local components of the correlation potential remain minimal. This comes at a large benefit, as the environment used in the quantum embedding approach is described by propagating correlated electrons and hence offers an exponentially increasing number of degrees of freedom for the embedding mapping, in contrast to traditional free-electron representation where the scaling is linear. We report that quantum impurity models with as few as 3 bath sites can reproduce both the Mott transition and the Kondo physics, thus opening a more accessible route to the description of time-dependent phenomena. Finally, we obtain excellent agreement for dynamical magnetic susceptibilities, poising this approach as a candidate to describe 2-particle excitations such as excitons in correlated systems. We expect that our approach will be highly beneficial for the implementation of embedding algorithms on quantum computers, as it allows for a fine description of the correlation in materials with a reduced number of required qubits.

The magnetization and magnetic susceptibility of GaAs Gaussian quantum dot with donor impurity in a magnetic field

We present a theoretical study to investigate the effect of donor impurity on the magnetization (M) and the magnetic susceptibility [Formula: see text] of single electron quantum dot (QD) with Gaussian confinement in the presence of a magnetic field. We solve the Hamiltonian of this system, including the spin, by using the exact diagonalization method. The ground state binding energy (BE) of an electron has been shown as a function of QD radius and confinement potential depth. The behaviors of the magnetization and the magnetic susceptibility of a QD have been studied as a function of temperature, confinement potential depth, quantum radius and magnetic field. We have shown the effect of donor impurity on the magnetization and magnetic susceptibility curves of Gaussian quantum dot (GQD).

The electronic states and magnetization of coupled AlGaAs/GaAs quantum dots in magnetic fields

We present a theoretical study of electronic states and magnetization of two interacting electrons confined in coupled quantum dots (CQDs) presented in a magnetic field. We obtain the eigenenergies of the CQD by solving the relative two-dimensional (2D) Hamiltonian using the combined variational–exact diagonalization method. The dependence of magnetization on temperature, magnetic field strength, confining frequency and barrier height has been investigated. We have shown the singlet–triplet transitions in the ground state of the CQD spectra and the corresponding jumps in the magnetization curves. The comparisons show that our results are in very good agreement with the reported works.

Few-electron quantum-dot spintronics

This article examines the spin and charge properties of double and triple quantum dots (QDs) populated containing just a few electrons, with particular emphasis on laterally coupled QDs. It first describes the theoretical approach, known as exact diagonalization method, utilized on the example of the two-electron system in coupled QDs that are modelled as two parabolas. The many-body problem is solved via the exact diagonalization method as well as variational Heitler–London and Monte Carlo methods. The article proceeds by considering the general characteristics of the two-electron double-QD structure and limitations of the approximate methods commonly used for its theoretical description. It also discusses the stability diagram for two circular dots and investigates how its features are affected by the QD elliptical deformations. Finally, it assesses the behavior of the two-electron system in the realistic double-dot confinement potentials.

The Effects of Pressure and Temperature on the Magnetic Susceptibility of Semiconductor Quantum Dot in A Magnetic Field

In this work, we present a theoretical study of the magnetic susceptibility (x of two-electron GaAs parabolic quantum dot (QD) under the combined effects of external pressure, temperature and magnetic field. We used the exact diagonalization method to obtain the eigenenergies by solving the two electron quantum dot Hamiltonian taking into account the dependence of the effective mass and dielectric constant on the hydrostatic pressure and temperature. The pressure and temperature show significant effects on the calculated QD spectra. Next, we investigate the behavior of the magnetization of a quantum dot as a function of external pressure, temperature, confining frequency and magnetic field. The singlet-triplet transitions in the ground state of the quantum dot spectra and the corresponding jumps in the magnetic susceptibility spectra have been shown. The comparison shows that our results are in very good agreement with the reported works.