Large Second-Order Josephson Effect in Planar Superconductor-Semiconductor Junctions

P. Zhang (1) , A. Zarassi (1) , L. Jarjat (2) , V. van de Sande (3) , M. Pendharkar (4) , J. S. Lee (4) , C. P. Dempsey (4) , A. P. Mcfadden (4) , S. D. Harrington (4) , J. T. Dong (4) , H. Wu (1) , A. -H. Chen (5) , Moïra Hocevar (5) , C. J. Palmstrøm (4) , S. M. Frolov (1)

1 PITT - University of Pittsburgh
2 Département de Physique de l'ENS-PSL
3 TU/e - Eindhoven University of Technology [Eindhoven]
4 UC Santa Barbara - University of California [Santa Barbara]
5 NEEL - NPSC - Nanophysique et Semiconducteurs

We investigate the current-phase relations of Al/InAs-quantum well planar Josephson junctions fabricated using nanowire shadowing technique. Based on several experiments, we conclude that the junctions exhibit an unusually large second-order Josephson harmonic, the $\sin(2\varphi)$ term. First, superconducting quantum interference devices (dc-SQUIDs) show half-periodic oscillations, tunable by gate voltages as well as magnetic flux. Second, Josephson junction devices exhibit kinks near half-flux quantum in supercurrent diffraction patterns. Third, half-integer Shapiro steps are present in the junctions. Similar phenomena are observed in Sn/InAs quantum well devices. We perform data fitting to a numerical model with a two-component current phase relation, however the microscopic origins of the observed effect remain to be understood. We consider alternative explanations which can account for some but not all of the evidence.

Domaines: Matière Condensée [cond-mat]

P. Zhang, A. Zarassi, L. Jarjat, V. van de Sande, M. Pendharkar, et al.. Large Second-Order Josephson Effect in Planar Superconductor-Semiconductor Junctions. SciPost Physics, 2024, 16 (1), pp.030. ⟨10.21468/SciPostPhys.16.1.030⟩. ⟨hal-03857774⟩