Nonlinear optical diode effect in a magnetic Weyl semimetal

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nonlinear Optics

Background:

• Diode effects, or nonreciprocal transport, are crucial for fundamental physics and technology.
• While electrical diode effects exist in Weyl systems, optical diode effects remain experimentally unverified.
• Magnetic topological materials offer potential for novel optical and transport phenomena.

Purpose of the Study:

• To experimentally observe and characterize nonlinear optical diode effects (NODE) in magnetic Weyl semimetals.
• To investigate the origin of the observed NODE and its dependence on material properties.
• To demonstrate electrical control over the NODE for potential device applications.

Main Methods:

• Experimental observation of nonlinear optical second-harmonic generation (SHG) in CeAlSi.
• Measurement of SHG intensity under varying propagation directions and bandwidths.
• Density-functional theory (DFT) calculations to elucidate the underlying physics.
• Demonstration of current-induced magnetization switching for electrical control.

Main Results:

• Observation of a pronounced nonlinear optical diode effect (NODE) in the magnetic Weyl semimetal CeAlSi.
• A six-fold change in SHG intensity between opposite propagation directions over a >250 meV bandwidth.
• Identification of linearly dispersive bands from Weyl nodes as the source of the broadband effect.
• Successful demonstration of electrical control of the NODE via current-induced magnetization switching.

Conclusions:

• The study provides the first experimental evidence of a nonlinear optical diode effect in magnetic topological materials.
• The findings establish CeAlSi as a promising material for exploring novel nonlinear optical phenomena.
• The demonstrated electrical control opens avenues for unidirectional light manipulation and advanced optical devices.