Radiation of spin excitations in the nonlinear transport regime

and

conductance peak in quantum wires

Maxim Kharitonov
Materials Science Division, Argonne National Laboratory

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.