Presence of -Wave Pairing in Josephson Junctions Made of Twisted Ultrathin Flakes

Zhu，Yuying1,2; Liao，Menghan1; Zhang，Qinghua3; Xie，Hong Yi2; Meng，Fanqi3; Liu，Yaowu1; Bai，Zhonghua1; Ji，Shuaihua1,4; Zhang，Jin1; Jiang，Kaili1,4,5; Zhong，Ruidan6; Schneeloch，John6,7; Gu，Genda6; Gu，Lin3; Ma，Xucun1,2,4; Zhang，Ding1,2,4,8; Xue，Qi Kun1,2,4,9

2021-09-01

10.1103/PhysRevX.11.031011

Physical Review X   影响因子和分区

2160-3308

Since the discovery of high-temperature superconductivity in cuprates, Josephson junction based phase-sensitive experiments are believed and used to provide the most convincing evidence for determining the pairing symmetry. Regardless of different junction materials and geometries used, quantum tunneling involved in these experiments is essentially a nanoscale process, and thus, actual experimental results are extremely sensitive to atomic details of the junction structures. The situation has led to controversial results as to the nature of the pairing symmetry of cuprates: while in-plane junction experiments generally support -wave pairing symmetry, those based on out-of-plane (-axis) Josephson junctions between two rotated cuprate blocks favor -wave pairing. In this work, we revisit the -axis experiment by fabricating Josephson junctions with atomic-level control in their interface structure. We fabricate over 90 junctions of ultrathin (BSCCO) flakes by state-of-the-art exfoliation technique and obtain atomically flat junction interfaces in the whole junction regions as characterized by high-resolution transmission electron microscopy. Notably, the resultant uniform junctions at various twist angles all exhibit a single tunneling branch behavior, suggesting that only the first half of a unit cell on both sides of the twisted flakes is involved in the Josephson tunneling process. With such well-defined geometry and structure and the characteristic single tunneling branch, we repeatedly observe Josephson tunneling at a nominal twist angle of 45°, which is against the expectation from a purely -wave pairing scenario. Our results strongly favor the scenario of a persistent -wave order parameter in the junction.

SCI ; EI

英语

NI论文

其他

WOS:000674610500002

20213110701370

Bismuth compounds ; Copper compounds ; Interface states ; Josephson junction devices

Optical Devices and Systems:741.3 ; Classical Physics; Quantum Theory; Relativity:931 ; High Energy Physics; Nuclear Physics; Plasma Physics:932

2-s2.0-85111252864

Scopus

1.State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics,Tsinghua University,Beijing,100084,China
2.Beijing Academy of Quantum Information Sciences,Beijing,100193,China
3.Laboratory for Advanced Materials and Electron Microscopy,Beijing National Laboratory for Condensed Matter Physics,Institute of Physics,Chinese Academy of Sciences,Beijing,100190,China
4.Frontier Science Center for Quantum Information,Beijing,100084,China
5.Tsinghua-Foxconn Nanotechnology Research Center,Tsinghua University,Beijing,100084,China
6.Condensed Matter Physics and Materials Science Department,Brookhaven National Laboratory,Upton,11973,United States
7.Department of Physics and Astronomy,Stony Brook University,Stony Brook,11794,United States
8.RIKEN Center for Emergent Matter Science (CEMS),Wako,Saitama,351-0198,Japan
9.Southern University of Science and Technology,Shenzhen,518055,China

Zhu，Yuying,Liao，Menghan,Zhang，Qinghua,et al. Presence of -Wave Pairing in Josephson Junctions Made of Twisted Ultrathin Flakes[J]. Physical Review X,2021,11(3).

Zhu，Yuying.,Liao，Menghan.,Zhang，Qinghua.,Xie，Hong Yi.,Meng，Fanqi.,...&Xue，Qi Kun.(2021).Presence of -Wave Pairing in Josephson Junctions Made of Twisted Ultrathin Flakes.Physical Review X,11(3).

Zhu，Yuying,et al."Presence of -Wave Pairing in Josephson Junctions Made of Twisted Ultrathin Flakes".Physical Review X 11.3(2021).