Hall effect detection of time-reversal symmetry breaking under AC driving

In a four terminal sample microscopic time-reversibility leads to symmetry relations between resistance measurements where the role of current and voltage leads are exchanged. These reciprocity relations are a manifestation of general Onsager-Casimir symmetries in equilibrium systems. We investigate experimentally the validity of time reversal symmetry in a $GaAs/Ga_{1-x}Al_xAs$ Hall bar irradiated by an external AC field at zero magnetic fields. For inhomogeneous AC fields we find strong deviations from reciprocity relations and show that their origin can be understood from the the billiard model of a Hall junction. Under homogeneous irradiation the symmetry is more robust indicating that time-reversal symmetry is preserved.