Time-reversal symmetry breaking superconductivity between twisted cuprate superconductors

S Y Frank Zhao; Xiaomeng Cui; Pavel A Volkov; Hyobin Yoo; Sangmin Lee; Jules A Gardener; Austin J Akey; Rebecca Engelke; Yuval Ronen; Ruidan Zhong; Genda Gu; Stephan Plugge; Tarun Tummuru; Miyoung Kim; Marcel Franz; Jedediah H Pixley; Nicola Poccia; Philip Kim

doi:10.1126/science.abl8371

Time-reversal symmetry breaking superconductivity between twisted cuprate superconductors

Science. 2023 Dec 22;382(6677):1422-1427. doi: 10.1126/science.abl8371. Epub 2023 Dec 7.

Authors

S Y Frank Zhao^#¹, Xiaomeng Cui^#¹, Pavel A Volkov^{1

2

3}, Hyobin Yoo⁴, Sangmin Lee⁵, Jules A Gardener⁶, Austin J Akey⁶, Rebecca Engelke¹, Yuval Ronen¹, Ruidan Zhong⁷, Genda Gu⁷, Stephan Plugge⁸, Tarun Tummuru⁸, Miyoung Kim⁵, Marcel Franz⁸, Jedediah H Pixley², Nicola Poccia^{1

9}, Philip Kim¹

Affiliations

¹ Department of Physics, Harvard University, Cambridge, MA 02138, USA.
² Center for Materials Theory, Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854, USA.
³ Department of Physics, University of Connecticut, Storrs, CT 06269, USA.
⁴ Department of Physics, Institute of Emergent Materials, Sogang University, Seoul 04107, Korea.
⁵ Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Korea.
⁶ Center for Nanoscale Systems, Harvard University, Cambridge, MA 02138, USA.
⁷ Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY 11973, USA.
⁸ Department of Physics and Astronomy and Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
⁹ Leibniz Institute for Solid State and Materials Research Dresden (IFW Dresden), 01069 Dresden, Germany.

^# Contributed equally.

PMID: 38060675
DOI: 10.1126/science.abl8371

Abstract

Twisted interfaces between stacked van der Waals (vdW) cuprate crystals present a platform for engineering superconducting order parameters by adjusting stacking angles. Using a cryogenic assembly technique, we construct twisted vdW Josephson junctions (JJs) at atomically sharp interfaces between Bi₂Sr₂CaCu₂O₈₊_x crystals, with quality approaching the limit set by intrinsic JJs. Near 45° twist angle, we observe fractional Shapiro steps and Fraunhofer patterns, consistent with the existence of two degenerate Josephson ground states related by time-reversal symmetry (TRS). By programming the JJ current bias sequence, we controllably break TRS to place the JJ into either of the two ground states, realizing reversible Josephson diodes without external magnetic fields. Our results open a path to engineering topological devices at higher temperatures.