Abstract
The propagation of Dyakonov–Tamm waves guided by the planar interface of an isotropic topological insulator and a structurally chiral material, both assumed to be nonmagnetic, was investigated by numerically solving the associated canonical boundary-value problem. The topologically insulating surface states of the topological insulator were quantitated via a surface admittance , which significantly affects the phase speeds and the spatial profiles of the Dyakonov–Tamm waves. Most significantly, it is possible that a Dyakonov–Tamm wave propagates co-parallel to a vector in the interface plane, but no Dyakonov–Tamm wave propagates anti-parallel to . The left/right asymmetry, which vanishes for , is highly attractive for one-way on-chip optical communication.
Highlights
Dyakonov–Tamm waves are electromagnetic surface waves whose propagation is guided by the planar interface of two dielectric materials, one of which is isotropic and homogeneous whereas the second is anisotropic and periodically nonhomogeneous normal to the interface plane [1]
Theoretical investigation [14] has recently shown that left/right asymmetry can be introduced in Dyakonov-wave propagation by (i) endowing the isotropic, homogeneous, dielectric partnering material with topologically insulating surface states (TISS) [15,16,17] and (ii) choosing the anisotropic, homogeneous, dielectric partnering material to possess orthorhombic crystallographic symmetry such that no more than one of the three eigenvectors of its relative permittivity dyadic lies in the interface plane
We formulated and solved the boundary-value problem for electromagnetic surface waves guided by the planar interface of an structurally chiral material (SCM) and a topological insulator (TI), both materials assumed to be nonmagnetic
Summary
Dyakonov–Tamm waves are electromagnetic surface waves whose propagation is guided by the planar interface of two dielectric materials, one of which is isotropic and homogeneous whereas the second is anisotropic and periodically nonhomogeneous normal to the interface plane [1]. While the allowed directions of propagation of Dyakonov waves are confined to two minute angular sectors (typically, each less than 1° in width [8, 11]) in the interface plane, Dyakonov–Tamm waves were theoretically predicted not to suffer from that restriction. Theoretical investigation [14] has recently shown that left/right asymmetry can be introduced in Dyakonov-wave propagation by (i) endowing the isotropic, homogeneous, dielectric partnering material with topologically insulating surface states (TISS) [15,16,17] and (ii) choosing the anisotropic, homogeneous, dielectric partnering material to possess orthorhombic crystallographic symmetry such that no more than one of the three eigenvectors of its relative permittivity dyadic lies in the interface plane. Vectors are in boldface; dyadics are underlined twice; Cartesian unit vectors are identified as ux, uy, and uz; column vectors are in boldface and enclosed with square brackets; and matrixes are underlined twice and enclosed with square brackets
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