9 research outputs found
Unidirectional Invisibility and PT-Symmetry with Graphene
We investigate the reflectionlessness and invisibility properties in the
transverse electric (TE) mode solution of a linear homogeneous optical system
which comprises the -symmetric structures covered by graphene
sheets. We derive analytic expressions, indicate roles of each parameter
governing optical system with graphene and justify that optimal conditions of
these parameters give rise to broadband and wide angle invisibility. Presence
of graphene turns out to shift the invisible wavelength range and to reduce the
required gain amount considerably, based on its chemical potential and
temperature. We substantiate that our results yield broadband reflectionless
and invisible configurations for realistic materials of small refractive
indices, usually around , and of small thickness sizes with graphene
sheets of rather small temperatures and chemical potentials. Finally, we
demonstrate that pure -symmetric graphene yields invisibility at
small temperatures and chemical potentials.Comment: 20 pages, 1 table 17 figure
Broadband and Wide-Angle Invisibility with PT-Symmetric 2D-Weyl Semimetal
Inspired by the magnificent features of two-dimensional (2D) materials which
aroused much of the interest in recent materials science research, we study
PT-symmetric 2D Weyl semimetal (WSM) to reveal the broadband and wide-angle
invisible configurations in a PT-symmetric optical slab system. Desired
unidirectional reflectionlessness and invisibility phenomena is obtained by the
optimal control of system parameters. We unravel the mystery of broadband and
wide-angle invisibility in regular slab materials with finite refractive
indices by means of the plenary expressions. We show that materials whose
refractive indices relatively small (usually around ) give rise to
quite a lot broadband and wide-angle (almost all incidence angles) invisible
configurations. This is not observed with any 2D material other than 2D WSMs.
Our findings suggest a concrete expedience to experimental realizations in this
direction.Comment: 8 pages, 11 figure
Scattering Theory and -Symmetry
We outline a global approach to scattering theory in one dimension that
allows for the description of a large class of scattering systems and their
-, -, and -symmetries. In
particular, we review various relevant concepts such as Jost solutions,
transfer and scattering matrices, reciprocity principle, unidirectional
reflection and invisibility, and spectral singularities. We discuss in some
detail the mathematical conditions that imply or forbid reciprocal
transmission, reciprocal reflection, and the presence of spectral singularities
and their time-reversal. We also derive generalized unitarity relations for
time-reversal-invariant and -symmetric scattering
systems, and explore the consequences of breaking them. The results reported
here apply to the scattering systems defined by a real or complex local
potential as well as those determined by energy-dependent potentials, nonlocal
potentials, and general point interactions.Comment: Slightly expanded revised version, 38 page