Asymmetric JxB Heating Induced by Incident Angle and Scale Length in Relativistic Laser-Solid Interaction

Relativistic laser-solid interactions are central to generating high-energy-density (HED) plasmas and energetic electrons for applications ranging from inertial confinement fusion to compact radiation sources. In relativistic regime, energy coupling at steep plasma boundaries is generally attributed to J×B heating, Characterized by 2ω electron bunching. However, our Particle-In-Cell (PIC) simulations at relativistic laser intensities reveal that this canonical feature becomes asymmetric or even transitions into a 1ω structure, depending on the angle of incidence and pre-plasma scale lengths. This transition originated from an asymmetric energy exchange between electrons and the laser’s electric field influenced by both scale length and angle of incidence. We introduce a simple model to quantify energy loss mechanism, clarify how it suppresses conventional JxB heating while reshaping the hot electron phase-space. These results provide deeper insights into energy deposition in relativistic laser-plasma interaction, and offer guidance for tailoring hot electron beams and optimizing laser-driven secondary sources in solid-density targets.