Momentum-resolved superconducting energy gaps of SrRuO from quasiparticle interference imaging.

SrRuO has long been the focus of intense research interest because of conjectures that it is a correlated topological superconductor. It is the momentum space (-space) structure of the superconducting energy gap [Formula: see text] on each band that encodes its unknown superconducting order parameter. However, because the energy scales are so low, it has never been possible to directly measure the [Formula: see text] of SrRuO Here, we implement Bogoliubov quasiparticle interference (BQPI) imaging, a technique capable of high-precision measurement of multiband [Formula: see text] At = 90 mK, we visualize a set of Bogoliubov scattering interference wavevectors [Formula: see text] consistent with eight gap nodes/minima that are all closely aligned to the [Formula: see text] crystal lattice directions on both the α and β bands. Taking these observations in combination with other very recent advances in directional thermal conductivity [E. Hassinger , 7, 011032 (2017)], temperature-dependent Knight shift [A. Pustogow , 574, 72-75 (2019)], time-reversal symmetry conservation [S. Kashiwaya , , 100, 094530 (2019)], and theory [A. T. Rømer , 123, 247001 (2019); H. S. Roising, T. Scaffidi, F. Flicker, G. F. Lange, S. H. Simon, 1, 033108 (2019); and O. Gingras, R. Nourafkan, A. S. Tremblay, M. Côté, 123, 217005 (2019)], the BQPI signature of SrRuO appears most consistent with [Formula: see text] having [Formula: see text] [Formula: see text] symmetry.