Superconducting diode effect (SDE) is a switching between the superconducting and normal current in asymmetric superconductors [1-4]. Symmetry plays important roles in the emergence of SDE but the effect of crystal symmetry, particularly in the context of zero-magnetic field SDE, is still elusive. In this work, we report a strain-controlled SDE in a van der Waals layered trigonal superconductor PbTaSe₂. The SDE is demonstrated exclusively in a strained PbTaSe₂ device while it is absent in an unstrained device, implying the critical role of broken three-fold rotational symmetry induced by the strain. Furthermore, the zero-field or magnetic field-even (magnetic field-odd) SDE is demonstrated when the device is strained and current flows in the armchair (zigzag) direction. This current directional dependence is consistent with the crystal symmetry, providing a firm evidence for the intrinsic nature of the observed SDE.

[1] F. Ando et al., Nature 584, 373–376 (2020).

[2] N. F. Q. Yuan & L. Fu, PNAS 119, e2119548119 (2022).

[3] H. Wu et al., Nature 604, 653–656 (2022).

[4] K. Misaki & N. Nagaosa, PRB 103, 245302 (2021).