Edge currents as probe of topology in twisted cuprate bilayers

Bilayers made of high-Tc cuprate superconductor Bi₂Sr₂CaCu₂O₈₊ₓ assembled with a twist angle close to 45^∘ have been recently shown to spontaneously break time reversal symmetry T, consistent with theoretical predictions for emergent chiral topological dx²-y²+idxy phase in such twisted d-wave superconductors. Here we use a minimal microscopic model to estimate the size of spontaneous chiral edge currents expected to occur in the T-broken phase. In accord with previous theoretical studies of chiral d-wave superconductors we find small but non-vanishing edge currents which we nevertheless predict to be above the detection threshold of the state-of-the-art magnetic scanning probe microscopy. In addition, by deriving a simple relation between the edge current and the electron spectral function we help elucidate the longstanding disparity between the size of edge currents in chiral d-wave and p-wave superconductors.