Radiation of spin excitations in the nonlinear transport regime
conductance peak in quantum
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.