期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2020
卷号：117
期号：10
页码：5222-5227
DOI：10.1073/pnas.1916463117
出版社：The National Academy of Sciences of the United States of America
摘要：Sr2 RuO4 has long been the focus of intense research interest because of conjectures that it is a correlated topological superconductor. It is the momentum space ( k -space) structure of the superconducting energy gap Δ i ( k ) on each band i that encodes its unknown superconducting order parameter. However, because the energy scales are so low, it has never been possible to directly measure the Δ i ( k ) of Sr2 RuO4 . Here, we implement Bogoliubov quasiparticle interference (BQPI) imaging, a technique capable of high-precision measurement of multiband Δ i ( k ) . At T = 90 mK, we visualize a set of Bogoliubov scattering interference wavevectors q j : j = 1 − 5 consistent with eight gap nodes/minima that are all closely aligned to the ( ± 1 , ± 1 ) 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 et al. , Phys. Rev. X 7, 011032 (2017)], temperature-dependent Knight shift [A. Pustogow et al. , Nature 574, 72–75 (2019)], time-reversal symmetry conservation [S. Kashiwaya et al. , Phys. Rev B , 100, 094530 (2019)], and theory [A. T. Rømer et al. , Phys. Rev. Lett. 123, 247001 (2019); H. S. Roising, T. Scaffidi, F. Flicker, G. F. Lange, S. H. Simon, Phys. Rev. Res. 1, 033108 (2019); and O. Gingras, R. Nourafkan, A. S. Tremblay, M. Côté, Phys. Rev. Lett. 123, 217005 (2019)], the BQPI signature of Sr2 RuO4 appears most consistent with Δ i ( k ) having d x 2 − y 2 ( B 1 g ) symmetry.
关键词：strontium ruthenate ; quasiparticle interference ; superconducting energy gaps
