Magnetic field induced depolarisation of electron spins andmelting of a Wigner molecule in quantum-dot lithium

摘要

Using an exact-diagonalisation technique we study properties of quantum-dotrnlithium–a system of three Coulomb-interacting two-dimensional electrons in the harmonicoscillatorrnpotential–as a function of magnetic field and Coulomb interaction. In the regimernof strong interaction we find an interesting effect of depolarisation of electron spins by therngrowing magnetic field. The effect takes place at a critical magnetic field B=Bcrit whichrnis zero in the regime of weak interactions and typically about 10 mT (for GaAs parameters)rnat strong interactions. Physical properties of the dot resemble those of a Wigner molecule atrnB＜Bcrit and of a Fermi-liquid at B＞Bcrit, so that the effect can also be interpreted asrnthe melting of a Wigner molecule by magnetic field. We also calculate the magnetic field–rnCoulomb interaction diagram for the ground state of the system in a broad range of parameters.