Spin current and second harmonic generation in non-collinear magnetic systems: the hydrodynamic model

Area of Science:

• Condensed Matter Physics
• Spintronics
• Nonlinear Optics

Background:

• Nonlinear optical phenomena like second harmonic generation (SHG) are crucial in optics.
• Spin currents offer novel ways to manipulate electronic properties.

Purpose of the Study:

• To theoretically investigate SHG in a noncollinearly magnetized conductive medium with an equilibrium spin current.
• To elucidate the mechanism behind a novel double frequency signal generation attributed to spin current.

Main Methods:

• Utilized a hydrodynamic model to study the underlying physics.
• Analyzed the non-adiabatic spin polarization of conduction electrons induced by electromagnetic wave interactions.
• Investigated the conversion of spin current to electric current via the inverse spin Hall effect.

Main Results:

• Identified a novel SHG mechanism driven by spin current.
• Demonstrated that non-adiabatic spin polarization leads to a double-frequency spin current.
• Showed that this spin current generates detectable second harmonic radiation through the inverse spin Hall effect.

Conclusions:

• The study reveals a new pathway for SHG mediated by spin currents.
• This finding opens possibilities for advanced spintronic and optoelectronic devices.
• A potential experimental setup for detecting this effect is proposed.