Electric Field-Induced Nonreciprocal Directional Dichroism in a Time-Reversal-Odd Antiferromagnet

Area of Science:

• Condensed Matter Physics
• Materials Science
• Magnetism

Background:

• Antiferromagnets with broken time-reversal (T) symmetry exhibit ferromagnet-like properties without net magnetization.
• Certain T-odd antiferromagnets, like those with magnetic toroidal monopoles, are not accessible via typical ferromagnet phenomena such as the anomalous Hall effect.
• Accessing broken T symmetry in these systems requires alternative methods beyond conventional approaches.

Purpose of the Study:

• To investigate and demonstrate a novel method for probing T-odd antiferromagnets characterized by a magnetic toroidal monopole.
• To utilize electric field-induced nonreciprocal directional dichroism (E-induced NDD) to access the broken T symmetry in these materials.
• To visualize and understand the domain structures and their response to external fields in such antiferromagnets.

Main Methods:

• Employed electric field-induced nonreciprocal directional dichroism (E-induced NDD) as a unique nonreciprocal optical phenomenon.
• Experimentally detected E-induced NDD signals in the T-odd antiferromagnet Co₂SiO₄.
• Utilized spatially resolved E-induced NDD to visualize domain states and their magnetic field-induced behavior.

Main Results:

• Successfully detected E-induced NDD signals in Co₂SiO₄, confirming its T-odd nature and magnetic toroidal monopole structure.
• Visualized spatial distributions of T-domain states, which are related by the T operation.
• Observed the inversion of domain patterns under magnetic field application, explained by trilinear coupling via the piezomagnetic effect.

Conclusions:

• The study successfully demonstrates the utility of E-induced NDD for probing T-odd antiferromagnets with magnetic toroidal monopoles.
• Spatially resolved E-induced NDD provides a powerful tool for visualizing T-odd domain structures and their dynamics.
• The findings highlight unique functionalities and potential applications of T-odd antiferromagnets beyond conventional magnetic phenomena.