Positive magnetoresistance induced by hydrodynamic fluctuations in chiral media

We analyze the combined effects of hydrodynamic fluctuations and chiral magnetic effect (CME) for a chiral medium in the presence of a background magnetic field. Based on the recently developed non-equilibrium effective field theory, we show fluctuations give rise to a CME-related positive contribution to magnetoresistance, while the early studies without accounting for the fluctuations find a CME-related negative magnetoresistance. At zero axial relaxation rate, the fluctuations contribute to the transverse conductivity in addition to the longitudinal one.

The radiation from ultrafast point dipoles, moving uniformly near chiral media

The article discusses the features of the radiation of ultrafast point clusters of charged particles moving uniformly near a gyrotropic medium interface. It is shown that some types of electromagnetic radiation – transient and/or Cherenkov radiation – have the characteristics of superchiral fields. Therefore, they can be effectively used to study chiral structures (for example, to detect circular dichroism, the frequency characteristics of refractive indices), various materials, including biomaterials. Ultrafast (relativistic) particles can serve as a «tool» not only for studying the structure of various materials. They can also be used as «generators» of quasiparticles that determine the «dynamic» properties of the materials under study, as well as the features of their interaction with radiation of various nature and response to external influences. In this paper, some types of circularly polarized EM waves propagating in optically active (magnetoactive, naturally active, gyrotropic, and chiral) media are considered. Using the generalized reciprocity theorem for media characterized by the Hermitian permittivity tensor, we consider the transient and Cherenkov radiation excited by a uniformly moving bunch of charged particles when it crosses (or moves along) the interface of media, one of which is an optically active gyrotropic medium. It is shown that the superchiral electromagnetic fields of the transition and Cherenkov radiation of dipoles can serve as a source of chiral collective excitations in magnetoactive and naturally active media. The investigated mechanisms of interaction of electromagnetic radiation with chiral materials (structures and media) are one of the possible physical approaches to solving the problem of the chiral purity of the biosphere and to elucidate the factor of deracemization of the organic primeval environment. A new hypothesis is presented, suggesting that ultra-high-speed clumps of charged particles of cosmic origin can cause deracemization of the prebiosphere.

Enantio-sensitive unidirectional light bending

Structured light, which exhibits nontrivial intensity, phase, and polarization patterns in space, has key applications ranging from imaging and 3D micromanipulation to classical and quantum communication. However, to date, its application to molecular chirality has been limited by the weakness of magnetic interactions. Here we structure light’s local handedness in space to introduce and realize an enantio-sensitive interferometer for efficient chiral recognition without magnetic interactions, which can be seen as an enantio-sensitive version of Young’s double slit experiment. Upon interaction with isotropic chiral media, such chirality-structured light effectively creates chiral emitters of opposite handedness, located at different positions in space. We show that if the distribution of light’s handedness breaks left-right symmetry, the interference of these chiral emitters leads to unidirectional bending of the emitted light, in opposite directions in media of opposite handedness, even if the number of the left-handed and right-handed emitters excited in the medium is exactly the same. Our work introduces the concepts of polarization of chirality and chirality-polarized light, exposes the immense potential of sculpting light’s local chirality, and offers novel opportunities for efficient chiral discrimination, enantio-sensitive optical molecular fingerprinting and imaging on ultrafast time scales.

Zilch vortical effect for fermions

We consider the notion of zilch current that was recently discussed in the literature as an alternative helicity measure for photons. Developing this idea, we suggest the generalization of the zilch for the systems of fermions. We start with the definition of the photonic zilch current in chiral kinetic theory framework and work out field-theoretical definition of the fermionic zilch using the Wigner function formalism. This object has similar properties to the photonic zilch and is conserved in the non-interacting theory. We also show that, in full analogy with a case of photons, the fermionic zilch acquires a non-trivial contribution due to the medium rotation - zilch vortical effect (ZVE) for fermions. Combined with a previously studied ZVE for photons, these results form a wider set of chiral effects parameterized by the spin of the particles and the spin of the current. We briefly discuss the origin of the ZVE, its possible relation to the anomalies in the underlying microscopic theory and possible application for studying the spin polarization in chiral media.

Irreducible Cartesian Tensor Analysis of Harmonic Scattering from Chiral Fluids

Symmetry principles of several distinct kinds are revealingly engaged in an analysis focussing on third harmonic scattering, a current focus of research on nonlinear optics in chiral media. Analysis in terms of irreducible Cartesian tensors elucidates the detailed electrodynamical origin and character of the corresponding material properties. Considerations of fundamental charge, parity and time reversal (CPT) symmetry reveal the conditions for an interplay of transition multipoles to elicit a chiral response using circularly polarised pump radiation, and the symmetry of quantised angular momentum underpins the associated selection rules and angular distribution. The intrinsic structural symmetry of chiral scatterers determines their capacity to exhibit differential response. Exploiting permutational index symmetry in the response tensors enables quantitative assessment of the boundary values for experimentally measurable properties, including circular intensity differentials.