Zusammenfassung
In the usual Fock and Darwin formalism with a parabolic potential characterized by the confining energy is an element of (0) = h omega (0) approximate to 3.4 meV, but including explicitly also the Zeeman coupling between spin and magnetic field, we study the combined orbital and spin magnetic properties of quantum dots in a two-dimensional electron gas with the parameters for GaAs, for N = 1 and ...
Zusammenfassung
In the usual Fock and Darwin formalism with a parabolic potential characterized by the confining energy is an element of (0) = h omega (0) approximate to 3.4 meV, but including explicitly also the Zeeman coupling between spin and magnetic field, we study the combined orbital and spin magnetic properties of quantum dots in a two-dimensional electron gas with the parameters for GaAs, for N = 1 and N much greater than I electrons on the dot. For N = 1 the magnetization M(T, B) consists of a paramagnetic spin contribution and a diamagnetic orbital contribution, which dominate in a nontrivial way at low temperatures and fields and at high temperatures and fields respectively. For N much greater than 1, where orbital and spin effects are intrinsically coupled in a subtle way and cannot be separated, we find in a simplified Hartree approximation that at N = m(2), i.e. for a half-filled last shell, M(T, B, N) is parallel (antiparallel) to the magnetic field, if temperatures and fields are low enough thigh enough), whereas for N P m2 the magnetization oscillates with B and N as a T-dependent periodic function of the variable x root NeB/(2m*c omega (0)), with T-independent period Deltax = 1 (where m* = 0.067 m(0) is the small effective mass of GaAs, while mo is the electron mass). Correspondingly, by an adiabatic demagnetization process, which need only be fast enough with respect to the slow transient time of the magnetic properties of the dot, the temperature of the dot diminishes or increases with decreasing magnetic field, and in some cases we obtain quite pronounced effects.
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