I will discuss transport of interacting electrons through a Y junction ("three-way junction") of quantum wires beyond the linear-response regime. Specifically, I will focus on the phenomenon of "emergent chirality," a distilled example of which is the emergence of a current in one of the wires ("side wire") attached symmetrically to two other wires biased symmetrically. The interaction-induced current does not depend on the sign of the voltage and is exactly zero in the linear response. This is an essentially nonequilibrium phenomenon which breaks time-reversal and/or parity symmetry that exists at the level of the Hamiltonian of the system. The concept of emergent chirality is precise in that the nonequilibrium symmetry breaking---which describes an effective Hall and/or "photogalvanic" response---is inherently linked to the chirality of the current, i.e., its "unidirectionality" when the polarity of all voltages is changed to the opposite.

This work was done in collaboration with D. Aristov, I. Gornyi, and P. Wölfle