Quantum size effects in ultra-thin YBa2Cu3O7 − x films

Scientific Reports, vol. 14, pp. 22174

Abstract

Abstract The d-wave symmetry of the order parameter with zero energy gap in nodal directions stands in the way of using high-temperature superconductors for quantum applications. We investigate the symmetry of the order parameter in ultra-thin YBa2Cu3O7 − x (YBCO) films by measuring the electrical transport properties of nanowires aligned at different angles relative to the main crystallographic axes. The anisotropy of the nanowire critical current in the nodal and antinodal directions reduces with the decrease in the film thickness. The Andreev reflection spectroscopy of the nanoconstrictions shows the presence of a thickness-dependent energy gap that does not exist in bulk YBCO. We find that the thickness-dependent energy gap appears due to the quantum size effects in ultra-thin YBCO films that open the energy gap along the entire Fermi surface. The fully gapped state of the ultra-thin YBCO films makes them a promising platform for quantum applications, including quantum computing and quantum communications.

Authors 7

1. Matvey Lyatti corresponding Aachen JARA-Fundamentals of Future Information Technology

   Forschungszentrum Jülich · Jülich Aachen Research Alliance · RWTH Aachen University

   Affiliation as printed

   JARA-Fundamentals of Future Information Technology, Jülich-Aachen Research Alliance , Forschungszentrum Jülich and RWTH Aachen University, Jülich, Germany. m.lyatti@fz-juelich.de

   Peter Grünberg Institut (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany. m.lyatti@fz-juelich.de

2. I. Gundareva Aachen JARA-Fundamentals of Future Information Technology

   Forschungszentrum Jülich · Jülich Aachen Research Alliance · RWTH Aachen University

   Affiliation as printed

   JARA-Fundamentals of Future Information Technology, Jülich-Aachen Research Alliance , Forschungszentrum Jülich and RWTH Aachen University, Jülich, Germany

   Peter Grünberg Institut (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany

3. Torsten Röper Aachen JARA-Fundamentals of Future Information Technology

   Forschungszentrum Jülich · Jülich Aachen Research Alliance · RWTH Aachen University

   Affiliation as printed

   JARA-Fundamentals of Future Information Technology, Jülich-Aachen Research Alliance , Forschungszentrum Jülich and RWTH Aachen University, Jülich, Germany

   Peter Grünberg Institut (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany

4. Zorica Popović

   University of Belgrade

   Affiliation as printed

   Faculty of Physics, University of Belgrade, Studentski trg. 12, Belgrade, 11001, Serbia

5. Abdur Rehman Jalil Aachen JARA-Fundamentals of Future Information Technology

   Forschungszentrum Jülich · Jülich Aachen Research Alliance · RWTH Aachen University

   Affiliation as printed

   JARA-Fundamentals of Future Information Technology, Jülich-Aachen Research Alliance , Forschungszentrum Jülich and RWTH Aachen University, Jülich, Germany

   Peter Grünberg Institut (PGI-10), Forschungszentrum Jülich, 52425, Jülich, Germany

6. Detlev Grützmacher

   Forschungszentrum Jülich

   Affiliation as printed

   Peter Grünberg Institut (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany

7. Thomas Schäpers Aachen JARA-Fundamentals of Future Information Technology

   Forschungszentrum Jülich · Jülich Aachen Research Alliance · RWTH Aachen University

   Affiliation as printed

   JARA-Fundamentals of Future Information Technology, Jülich-Aachen Research Alliance , Forschungszentrum Jülich and RWTH Aachen University, Jülich, Germany

   Peter Grünberg Institut (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany