Radiation of spin excitations in the nonlinear
transport regime
and
conductance peak in quantum
wires
Maxim Kharitonov
Materials Science Division,
We study the role of spin
excitations on the electron transport through a long quantum wire smoothly
connected to the leads in the nonlinear regime of applied current. At low
electron density in the wire, electrons arrange themselves into a
near-ordered Wigner crystal and the spin excitations may
be described by the Heisenberg chain of electron spins positioned at the sites
of the crystal. A novel threshold effect is predicted: above a certain
value of the applied current, when the electron drift velocity exceeds
the velocity of spin excitations in the wire, the spin excitations
incoming from the leads start to scatter on the constriction connecting
the wire to the leads and get partially reflected back into the leads.
The energy dissipation associated with these scattering processes results
in a peak-like structure in the differential conductance around zero bias
voltage. The predicted effect could serve as an explanation for the
conductance peak in quantum wires commonly
observed in the experiments.