Edge currents as probe of topology in twisted cuprate bilayers

Abstract

Bilayers made of the 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 nonvanishing edge currents whose magnitude and spatial distribution are sensitive to the type of the edge or domain wall. We nevertheless predict these 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.

Source-reported materials — not catalogue approval

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