Quantum spin Hall effect of light

By K. Bliokh, D. Smirnova, Franco Nori. Science, 2015

745 citations recorded by the source corpus.

A quantum twist on classical optics Interpreting recent experimental results of light interactions with matter shows that the classical Maxwell theory of light has intrinsic quantum spin Hall effect properties even in free space. Complex effects in condensed-matter systems can often find analogs in cleaner optical systems. Bliokh et al. argue that the optical systems exhibiting such complex phenomena should also be simpler (see the Perspective by Stone). Their theoretical study shows that free-space light has a nonzero topological spin Chern number and thus should have counterpropagating surface modes. Such modes are actually well known and can be described as evanescent modes of Maxwell equations. Science, this issue p. 1448; see also p. 1432 A theoretical study reveals that quantum effects may manifest in classical optical experiments. [Also see Perspective by Stone] Maxwell’s equations, formulated 150 years ago, ultimately describe properties of light, from classical electromagnetism to quantum and relativistic aspects. The latter ones result in remarkable geometric and topological phenomena related to the spin-1 massless nature of photons. By analyzing fundamental spin properties of Maxwell waves, we show that free-space light exhibits an intrinsic quantum spin Hall effect—surface modes with strong spin-momentum locking. These modes are evanescent waves that form, for example, surface plasmon-polaritons at vacuum-metal interfaces. Our findings illuminate the unusual transverse spin in evanescent waves and explain recent experiments that have demonstrated the transverse spin-direction locking in the excitation of surface optical modes. This deepens our understanding of Maxwell’s theory, reveals analogies with topological insulators for electrons, and offers applications for robust spin-directional optical interfaces.

Subfields: Atomic and Molecular Physics, and Optics, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/3c1c392689561b655d483dfce93ef20f208df9a2

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Citations in the corpus

Topological photonics (2018, background): “This is an intrinsic coupling between the orbital and spin degrees of freedom for light, underlying a wide range of phenomena (Bliokh et al., 2015).”
Symmetry and Topology in Non-Hermitian Physics (2018, neutral): “[191] K.”
Colloquium: Strongly interacting photons in one-dimensional continuum (2016, background): “Bliokh et al. (2015) argue that the transverse spin in evanescent waves and the spin-controlled directional excitation of surface or waveguide modes is analogous to the quantum spin Hall effect.”
Geometric phase from Aharonov–Bohm to Pancharatnam–Berry and beyond (2019, background): “in spin-orbit coupling has been observed in evanescent waves upon total internal reflection. These effects have been investigated theoretically and observed experimentally under various circumstances (143,144,145,146). Using this optical spin-orbit coupling resulting from a geometric phase, several ”
Nonseparable States of Light: From Quantum to Classical (2022, background): “As a first example, the quantum spin angular momentum (SAM) state corresponds to the circular polarization state of light [36].”
Transverse and longitudinal angular momenta of light (2015, background): “Recently it was shown that this property can be associated with the intrinsic quantum spin Hall effect of light, which originates from the spin–orbit coupling and topological properties of photons [56].”
Three-dimensional all-dielectric photonic topological insulator (2016, background): “Electromagnetic duality is a natural property of the electromagnetic field in free space which reflects symmetry of nature with respect to the electric and magnetic components of electromagnetic waves [ 46].”
Structured Light: Ideas and Concepts (2020, background): “In this view, the possibilities for the controllable SPP excitation and propagation are in the focus of current research [12, 95].”