Showing papers by "Xiao Lin published in 2017"

All-angle negative refraction of highly squeezed plasmon and phonon polaritons in graphene–boron nitride heterostructures

Abstract: A fundamental building block for nanophotonics is the ability to achieve negative refraction of polaritons, because this could enable the demonstration of many unique nanoscale applications such as deep-subwavelength imaging, superlens, and novel guiding. However, to achieve negative refraction of highly squeezed polaritons, such as plasmon polaritons in graphene and phonon polaritons in boron nitride (BN) with their wavelengths squeezed by a factor over 100, requires the ability to flip the sign of their group velocity at will, which is challenging. Here we reveal that the strong coupling between plasmon and phonon polaritons in graphene-BN heterostructures can be used to flip the sign of the group velocity of the resulting hybrid (plasmon-phonon-polariton) modes. We predict all-angle negative refraction between plasmon and phonon polaritons and, even more surprisingly, between hybrid graphene plasmons and between hybrid phonon polaritons. Graphene-BN heterostructures thus provide a versatile platform for the design of nanometasurfaces and nanoimaging elements.

Splashing transients of 2D plasmons launched by swift electrons

Abstract: We predict a jet-like rise of excessive charge concentration that delays 2D plasmon generation in electron-energy-loss spectroscopy; revealing an analogy to the Rayleigh jet in a splashing phenomenon prior to the launching of ripples.

Confined transverse electric phonon polaritons in hexagonal boron nitrides

Abstract: We predict the existence of confined transverse electric (TE) phonon polaritons in an ultrathin hexagonal boron nitride (hBN) slab below hBN's second transverse optical frequency. The skin depth of TE phonon polaritons can be decreased to subwavelength scale by increasing the thickness of hBN to several nanometers. Due to the strong spatial confinement, these TE phonon polaritons, different from TE graphene plasmons, can stably exist even when the permittivities of the superstrate and substrate are largely different. These revealed advantages of TE phonon polaritons might lead to potential applications of hBN in the manipulation of TE waves, such as the design of novel waveguides, polarizers, and the exploration of negative refraction between TE polaritons.

Design of Ultracompact Graphene-Based Superscatterers

Abstract: The energy-momentum dispersion relation is a fundamental property of plasmonic systems. In this paper, we show that the method of dispersion engineering can be used for the design of ultracompact graphene-based superscatterers. Based on the Bohr model, the dispersion relation of the equivalent planar waveguide is engineered to enhance the scattering cross section of a dielectric cylinder. Bohr conditions with different orders are fulfilled in multiple dispersion curves at the same resonant frequency. Thus, the resonance peaks from the first- and second-order scattering terms are overlapped in the deep-subwavelength scale by delicately tuning the gap thickness between two graphene layers. Using this ultracompact graphene-based superscatterer, the scattering cross section of the dielectric cylinder can be enhanced by five orders of magnitude.

Hybrid Airy plasmons with dynamically steerable trajectories.

Abstract: With their intriguing diffraction-free, self-accelerating, and self-healing properties, Airy plasmons show promise for use in the trapping, transporting, and sorting of micro-objects, imaging, and chip scale signal processing However, high dissipative loss and lack of dynamical steerability restrict the implementation of Airy plasmons in these applications Here we reveal hybrid Airy plasmons for the first time by taking a hybrid graphene-based plasmonic waveguide in the terahertz (THz) domain as an example Due to coupling between optical modes and plasmonic modes, the hybrid Airy plasmons can have large propagation lengths and effective transverse deflections, where the transverse waveguide confinements are governed by the hybrid modes with moderate quality factors Meanwhile, the propagation trajectories of the hybrid Airy plasmons are dynamically steerable by changing the chemical potential of graphene These hybrid Airy plasmons may promote the further discovery of non-diffracting beams along with the emerging developments of optical tweezers and tractor beams

Ab initio electronic transport study of two-dimensional silicon carbide-based p–n junctions*

Abstract: Two-dimensional silicon carbide (2d-SiC) is a viable material for next generation electronics due to its moderate, direct bandgap with huge potential. In particular, its potential for p-n junctions is yet to be explored. In this paper, three types of 2d-SiC-based p-n junctions with different doping configuration are modeled. The doping configurations refer to partially replacing carbon with boron or nitrogen atoms along the zigzag or armchair direction, respectively. By employing density functional theory, we calculate the transport properties of the SiC based p-n junctions and obtain negative differential resistance and high rectification ratio. We also find that the junction along the zigzag direction with lower doping density exhibits optimized rectification performance. Our study suggests that 2d-SiC is a promising candidate as a material platform for future nano-devices.

All-angle negative refraction of highly squeezed polaritons in graphene-boron nitride heterostructures

Abstract: Graphene-boron nitride (BN) heterostructures provide a versatile platform to flexibly tune the sign of the group velocity of the hybrid plasmon-phonon-polaritons, enabling all-angle negative refraction between graphene plasmons, BN's phonon polaritons and their hybrid polaritons.