1 research outputs found
Restricted and unrestricted Hartree-Fock calculations of conductance for a quantum point contact
Very short quantum wires (quantum contacts) exhibit a conductance structure
at a value of conductance close to . It is believed that the
structure arises due to the electron-electron interaction, and it is also
related to electron spin. However details of the mechanism of the structure are
not quite clear. Previously we approached the problem within the restricted
Hartree-Fock approximation. This calculation demonstrated a structure similar
to that observed experimentally. In the present work we perform restricted and
unrestricted Hartree-Fock calculations to analyze the validity of the
approximations. We also consider dependence of the effect on the electron
density in leads. The unrestricted Hartree-Fock method allows us to analyze
trapping of the single electron within the contact. Such trapping would result
in the Kondo model for the ``0.7 structure''. The present calculation confirms
the spin-dependent bound state picture and does not confirm the Kondo model
scenario.Comment: 6 pages, 9 figure