Suchergebnisse

We discuss optical chirality in different types of gyrotropic media. Our analysis is based on the formalism of nongeometric symmetries of Maxwell's equations in vacuum generalized to material media with given constituent relations. This approach enables us to directly derive conservation laws related to nongeometric symmetries. For isotropic chiral media, we demonstrate that like a free electromagnetic field, both duality and helicity generators belong to the basis set of nongeometric symmetries that guarantees the conservation of optical chirality. In gyrotropic crystals, which exhibit natural optical activity, the situation is quite different from the case of isotropic media. For light propagating along a certain crystallographic direction, there arises two distinct cases: (1) the duality is broken but the helicity is preserved, or (2) only the duality symmetry survives. We show that the existence of one of these symmetries (duality or helicity) is enough to define optical chirality. In addition, we present examples of low-symmetry media, where optical chirality cannot be defined. © 2017 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft. ; This work was supported by the Government of the Russian Federation Program 02.A03.21.0006 and by RFBR Grant No. 17-52-50013. The authors also acknowledge support by JSPS KAKENHI Grants Nos. 25220803, 17H02923, the JSPS Core-to-Core Program, A. Advanced Research Networks, and the JSPS Bilateral (Japan-Russia) Joint Research Projects. IP acknowledges financial support by Center for Chiral Science, Hiroshima University and by the Ministry of Education and Science of the Russian Federation, Grant No. MK-6230.2016.2.

We consider the case of a chiral soliton lattice subjected to uniaxial elastic strain applied perpendicular to the chiral axis and derive through analytical modeling the phase diagram of magnetic states supported in the presence of an external magnetic field. The strain induced anisotropies give rise to three distinct nontrivial spin textures, depending on the nature of the strain, and we show how these states may be identified by their signatures in Lorentz transmission electron microscopy (TEM). Experimental TEM measurements of the Fresnel contrast in a strained sample of the prototypical monoaxial chiral helimagnet CrNb3S6 are reported and compare well with the modeled contrast. Our results demonstrate an additional degree of freedom that may be used to tailor the magnetic properties of helimagnets for fundamental research and applications in the areas of spintronics and the emerging field of strain manipulated spintronics. © 2020 American Physical Society. ; This work was supported by a Grants-in-Aid for Scientific Research (B) (KAKENHI Grants No.17H02767 and No. 17H02923) from the MEXT of the Japanese Government, JSPS Bilateral Joint Research Projects (JSPS-FBR), the JSPS Core-to-Core Program, A. Advanced Research Networks, the Engineering and Physical Sciences Research Council (EPSRC) of the U.K. under Grant No. EP/M024423/1, and Grants-in-Aid for Scientific Research on Innovative Areas "Quantum Liquid Crystals" (KAKENHI Grant No. JP19H05826) from JSPS of Japan. I.P. and A.A.T. acknowledge financial support by the Ministry of Education and Science of the Russian Federation, Grant No. MK-1731.2018.2 and by the Russian Foundation for Basic Research (RFBR), Grant No. 18-32-00769 (mol_a). A.S.O. and A.A.T. acknowledge funding by the Foundation for the Advancement of Theoretical Physics and Mathematics BASIS Grant No. 17-11-107, and by Act 211 Government of the Russian Federation, Contract No. 02.A03.21.0006. A.S.O. thanks the Russian Foundation for Basic Research (RFBR), Grant 20-52-50005, and the Ministry of Education and Science of Russia, Project No. FEUZ-2020-0054.