Josephson diode effect: An interplay of strong second-order harmonic supercurrent and junction geometry

In Josephson junctions, broken inversion, and time-reversal symmetries can lead to the Josephson diode effect (JDE), i.e., nonreciprocal supercurrent transport. The JDE has attracted much attention for its potential application in superconducting circuits as a logic element. We study a quasi-two-dimensional junction consisting of two conventional s-wave superconductors sandwiching a Dirac semimetal, PtTe2. By studying the evolution of the magnetic interference patterns, we demonstrate a relatively large second-harmonic component in the Josephson supercurrent that serves as an essential ingredient for the existence of an "intrinsic" diode effect. The second-harmonic component modifies the Josephson penetration depth so that the supercurrent self-field may significantly affect the supercurrent flow in the junction. We show that this establishes an "extrinsic" contribution to the diode effect. We also show how the extrinsic JDE is affected by the Josephson junctions' geometry and bias design.