Spontaneous spin polarization of electrons in quantum wires

Abstract

The quantum conductance staircase of the one-dimensional (1D) channel is analyzed for a weak filling of the lower 1D subbands, when the exchange electron-electron interaction of carriers dominates over their kinetic energy. Main attention is paid to considering the behavior of the “0.7(2e 2/h)” feature split off from the first quantum step, which is identified as a result of the spontaneous spin polarization of the 1D electronic gas through exchange interaction at zero magnetic field. The critical linear concentration of electrons above which fully polarized electron gas starts to depolarize, with the resulting evolution of the split-off substep height from e 2/h to 2e 2/h, is determined within the framework of phenomenological theory. Moreover, the temperature dependence of the height of this substep at the range 0.5(2e 2/h)–0.75(2e 2/h), resulting from the partial depolarization of the electron gas near the 1D subband bottom, is predicted. The quantum-mechanical consideration carried out analytically in the context of the Hartree-Fock-Slater approximation with localized exchange potential shows that consideration of the electron-electron interaction in a quantum wire with an arbitrary carrier density leads to spontaneous polarization of the quasi-1D electronic gas in zero magnetic field at small linear concentrations of carriers.