Topological Phase Transitions in the Photonic Spin Hall Effect

Abstract

The recent synthesis of two-dimensional staggered materials opens up burgeoning opportunities to study optical spin-orbit interactions in semiconducting Dirac-like systems. We unveil topological phase transitions in the photonic spin Hall effect in the graphene family materials. It is shown that an external static electric field and a high frequency circularly polarized laser allow for active on-demand manipulation of electromagnetic beam shifts. The spin Hall effect of light presents a rich dependence with radiation degrees of freedom, material properties, and features non-trivial topological properties. We discover that photonic Hall shifts are sensitive to spin and valley properties of the charge carries, providing a unprecedented pathway to investigate spintronics and valleytronics in staggered 2D semiconductors.At macroscopic scales electromagnetic radiation's spatial and polarization degrees of freedom are independent quantities that can be accurately described by traditional geometric optics. A different landscape takes place in the subwavelength regime where emergent photonic spin-orbit interactions (SOI) culminate in spin-dependent changes in light's spatial properties [1,2]. A striking optical phenomena originating from SOI is the spin Hall effect of light (SHEL), which corresponds to the shift of photons with contrary chirality to opposite sides of a finite beam undergoing reflection/refraction [3][4][5][6]. The SHEL is universal to any interface and represents a remarkable failure of Fresnel's and Snell's formulas at the nanoscale. It exhibits a unique potential for applications in precision metrology, including bio-sensing [7], nanoprobing [8], and thin films and multilayer graphene characterization [9][10][11]. It has also been used to identify different absorption mechanisms in bulk semiconductors [12,13].Staggered two-dimensional semiconductors [14][15][16], including silicene [17], germanene [18], and stanene [19,20] are monolayer materials made of Silicon, Germanium, and Tin atoms, respectively, arranged in a honeycomb lattice. Unlike graphene [21], these materials are nonplanar and possess intrinsic spin-orbit coupling that results in the opening of a gap in their electronic band structure. Under the influence of external static and circularly polarized electromagnetic fields the four Dirac gaps are in general nondegenerate and the monolayer may be driven through several phase transitions involving topologically non-trivial states [22][23][24][25][26]. Previous studies on SHEL in the graphene family have been restricted to graphene [27][28][29], therefore overlooking the role of finite staggering, spin-orbit coupling, and spin/valley dynamics. The interplay between topological matter and SHEL was considered in magnetic field biased bulk materials with axion coupling [30]. In this letter we take advantage of the crossroads between topology, phase transitions, spin-orbit interactions, and Dirac physics in staggered 2D semiconductors to uncover magnetic field free topological phase transitions in...

Probing the Photonic Spin–Orbit Interactions in the Near Field of Nanostructures

“…The proposed one‐channel system and robust method may provide a powerful tool specifically for the near‐field characterization of novel spin‐based phenomena and nanodevices, such as the spin‐dependent topological photonics, and the spin–orbit photonics with 2D materials . By combining with other novel nanoprobes, it may also boost the advances in magnetic SOI of light, near‐field directionality, and even chiral quantum optics, to name a few.…”

Crossover of spin Hall to quantum anomalous Hall effect in PbC/MnSe heterostructures

“…In two-dimensional photonic crystal, a conventional insulator phase, a quantum spin Hall phase, or a quantum anomalous Hall phase can be realized by simply adjusting the geometric parameters and magnetic field [15,16]. Kort-Kamp [17] unveiled topological phase transitions in the photonic spin Hall effect in the graphene family materials. The spin Hall effect can be realized in a Bose-Einstein condensate of neutral atoms interacting via the magnetic dipole-dipole interactions [18].…”

Topological phase transitions and quantum Hall effect in the graphene family

“…They are also nonplanar, with their two inequivalent sublattices lying in two distinct parallel planes, and thus respond to the presence of an out-of-plane static electric field [12][13][14][15]. Together with a circularly polarized laser, these external fields allow one to tune the gap for each spin and valley, allowing the materials to be driven through several phase transitions [16][17][18][19]. Many of the achievable phases possess topologically nontrivial features that can be characterized by a topological invariant, namely, the charge Chern number.…”