Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Realization of broadband truly rainbow trapping in gradient-index
  heterostructures   Unidirectionally propagating waves (UPW) such as topologically protected edge
modes and surface magnetoplasmons (SMPs) has been a research hotspot in the
last decades. In the study of UPW, metals are usually treated as perfect
electric conductors (PECs) which, in general, are the boundary conditions.
However, it was reported that the transverse resonance condition induced by the
PEC wall(s) may significantly narrow up the complete one-way propagation (COWP)
band. In this paper, we propose two ways to achieve ultra-broadband one-way
waveguide in terahertz regime. The first way is utilizing the epsilon negative
(ENG) metamaterial (MM) and the other one is replacing the PEC boundary with
perfect magnetic conductor (PMC) boundary. In both conditions, the total
bandwidth of the COWP bands can be efficiently broadened by more than three
times. Moreover, based on the ultra-broadband one-way configurations,
gradient-index metamaterial-based one-way waveguides are proposed to achieve
broadband truly rainbow trapping (TRT). By utilizing the finite element method,
the realization of the broadband TRT without backward reflection is verified in
gradient-index structures. Besides, giant electric field enhancement is
observed in a PMC-based one-way structure with an ultra-subwavelength ($\approx
10^{-4} \lambda_0$, $\lambda_0$ is the wavelength in vaccum) terminal, and the
amplitude of the electric field is enormously enhanced by five orders of
magnitude. Our findings are beneficial for researches on broadband terahertz
communication, energy harvesting and strong-field devices.

24
The categories of this paper are: dg-ga
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
15
The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph
23
The categories of this paper are: solv-int
13
The categories of this paper are: quant-ph
6
The categories of this paper are: astro-ph
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
25
The categories of this paper are: patt-sol