Magnetic Field Free Magneto-optics and Chiral Plasmonics with Dirac Materials.
Reciprocity is a fundamental concept in optics. Basically, it says that if I can see you, then you can see me. It means that if a light rays can travel from A to B, then it can also follow this trajectory in the opposite direction, from B to A. However in optical communications, breaking this reciprocity is crucial to prevent interference and protecting optical sources. Non-reciprocal devices would allow the transmission of signals in one direction while blocking those propagating in the opposite direction.
Achieving non-reciprocity generally requires breaking time-reversal symmetry. This can be accomplished in magneto-optical materials under an external magnetic field. However, such devices tend to be bulky, costly and not CMOS compatible, motivating the on-going search for alternative strategies to break reciprocity for on-chip integration.
West Virginia University’s approach is to explore a new class of material, gapped Dirac materials such as single-layer transition metal dichalcogenides, where the breaking of inversion symmetry and large spin-orbit coupling leads to valley-spin locking. Their intrinsic Berry curvature further acts as an effective magnetic field in momentum space, giving rise to chiral plasmons at mid-IR and THz frequencies. Our goal is to achieve magnetic-field-free nonreciprocal light transport based on these properties.