Josephson coupling in high-Tc superconducting junctions using ultra-thin BaTiO3 barriers

H. NAVARRO; M. SIRENA,; JEEHOON KIM; N. HABERKORN

MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2020 vol. 262 p. 114714 - 114719

0921-5107

We study the electrical transport of vertically-stacked Josephson tunnel junctions using GdBa2Cu3O7−d electrodes and a BaTiO3 barrier with thicknesses between 1 nm and 3 nm. The junctions with an area of 20 mm x 20 mm were fabricated combining optical lithography and ion etching using GdBa2Cu3O7−d (16 nm) / BaTiO3 (1 - 3 nm) / GdBa2Cu3O7−d (16 nm) trilayers growth by sputtering on (100) SrTiO3. Current-voltage measurements at low temperatures show a Josephson coupling for junctions with BaTiO3 barriers of 1 nm and 2 nm. Reducing the barrier thickness bellow a critical thickness seems to suppress the ferroelectric nature of the BaTiO3. The Josephson coupling temperature is strongly reduced for increasing barrier thicknesses, which may be related to the suppression of the superconducting critical temperature in the bottom GdBa2Cu3O7−d due to stress. The Josephson energies at 12 K are of ≈ 1.5 mV and ≈ 7.5 mV for BaTiO3 barriers of 1 nm and 2 nm. Fraunhofer patterns are consistent with fluctuations in the critical current due to structural inhomogeneities in the barriers. Our results are promising for the development of Josephson junctions using high-Tc electrodes with energy gaps much higher than those usually present in conventional low-temperature superconductors.