91 research outputs found
Current-controlled light scattering and asymmetric plasmon propagation in graphene
We demonstrate that plasmons in graphene can be manipulated using a DC
current. A source-drain current lifts the forward/backward degeneracy of the
plasmons, creating two modes with different propagation properties parallel and
antiparallel to the current. We show that the propagation length of the plasmon
propagating parallel to the drift current is enhanced, while the propagation
length for the antiparallel plasmon is suppressed. We also investigate the
scattering of light off graphene due to the plasmons in a periodic dielectric
environment and we find that the plasmon resonance separates in two peaks
corresponding to the forward and backward plasmon modes. The narrower linewidth
of the forward propagating plasmon may be of interest for refractive index
sensing and the DC current control could be used for the modulation of
mid-infrared electromagnetic radiation.Comment: 5 pages, 5 figure
Optical signatures of nonlocal plasmons in graphene
We theoretically investigate under which conditions nonlocal plasmon response
in monolayer graphene can be detected. To this purpose, we study optical
scattering off graphene plasmon resonances coupled using a subwavelength
dielectric grating. We compute the graphene conductivity using the Random Phase
Approximation (RPA) obtaining a nonlocal conductivity and we calculate the
optical scattering of the graphene-grating structure. We then compare this with
the scattering amplitudes obtained if graphene is modeled by the local RPA
conductivity commonly used in the literature. We find that the graphene plasmon
wavelength calculated from the local model may deviate up to from the
more accurate nonlocal model in the small-wavelength (large-) regime. We
also find substantial differences in the scattering amplitudes obtained from
the two models. However, these differences in response are pronounced only for
small grating periods and low temperatures compared to the Fermi temperature.Comment: Accepted for publication in Physical Review B. 15 pages, 9 figure
High-sensitivity plasmonic refractive index sensing using graphene
We theoretically demonstrate a high-sensitivity, graphene-plasmon based
refractive index sensor working in the mid-infrared at room temperature. The
bulk figure of merit of our sensor reaches values above , but the key
aspect of our proposed plasmonic sensor is its surface sensitivity which we
examine in detail. We have used realistic values regarding doping level and
electron relaxation time, which is the limiting factor for the sensor
performance. Our results show quantitatively the high performance of
graphene-plasmon based refractive index sensors working in the mid-infrared.Comment: This is an author-created, un-copyedited version of an article
accepted for publication/published in 2DMaterials. IOP Publishing Ltd is not
responsible for any errors or omissions in this version of the manuscript or
any version derived from it. The Version of Record is available online at
https://doi.org/10.1088/2053-1583/aa70f
Nanomechanical mass measurement using nonlinear response of a graphene membrane
We propose a scheme to measure the mass of a single particle using the nonlinear response of a 2D nanoresonator with degenerate eigenmodes. Using numerical and analytical calculations, we show that by driving a square graphene nanoresonator into the nonlinear regime, simultaneous determination of the mass and position of an added particle is possible. Moreover, this scheme only requires measurements in a narrow frequency band near the fundamental resonance
Edge plasmons in graphene nanostructures
Plasmon modes in graphene are influenced by the unusual dispersion relation of the material. For bulk plasmons this results in a n(1/4) dependence of the plasma frequency on the charge density, as opposed to the n(1/2) dependence in two-dimensional electron gas (2DEG); yet, bulk plasmon dispersion in graphene follows a similar q(1/2) behavior as for other two-dimensional materials. In this work we consider finite graphene nanostructures, semi-infinite sheets, and circular disks and study edge plasmons that are confined to the boundaries of the structures. We find that, for abrupt edges, graphene edge plasmons behave analogously to those in 2DEGs, but, for gradual edge profiles, important distinctions arise. In particular, we show that for a linear edge profile, graphene supports fewer edge modes than a 2DEG at a given q, and the edge monopole plasmon dispersion in graphene follows a q(1/4) law in contrast to the q(0) behavior seen in 2DEGs. RAMOWITZ M, 196
Edge magnetoplasmons and the optical excitations in graphene disks
We discuss the edge magnetoplasmon properties in highly doped graphene disks, and the corresponding optical excitations. Edge magnetoplasmons with nonzero angular momentum (l not equal 0) have two branches corresponding to different edge current rotations with respect to the magnetic field. The resonance energies of one branch are blueshifted and the other redshifted relative to energies at B = 0, with the energy differences linearly proportional to the magnetic field. Recently, the l = 1 dipole mode has been investigated by two experiments using optical transmission spectroscopy [Crassee et al., Nano Lett. 12, 2470 (2012); Yan et al., ibid. 12, 3766 (2012)], and classical cyclotron resonances were found in highly doped graphene samples. These are determined by graphene magneto-optical conductivities, which behave like a conventional two-dimensional electron system in the high doping limit
Temperature-dependent resistance of a finite one-dimensional Josephson junction array
We study theoretically the temperature and array-length dependences of the resistance of a finite one-dimensional array of Josephson junctions. We use both analytic approximations and numerical simulations, and conclude that within the self-charging model, all finite arrays are resistive in the low-temperature limit. A heuristic analysis shows qualitative agreement with resistance obtained from Monte Carlo simulations, establishing a connection between resistance and the occurrence of vortices in the corresponding 1 +1D XY-model. We compare our results with recent experiments and conclude that while the self-charging model reproduces some of the experimental observations, it underestimates the superconducting tendencies in the experimental structures
Nonlinear damping in graphene resonators
Based on a continuum mechanical model for single-layer graphene, we propose and analyze a microscopic mechanism for dissipation in nanoelectromechanical graphene resonators. We find that coupling between flexural modes and in-plane phonons leads to linear and nonlinear damping of out-of-plane vibrations. By tuning external parameters such as bias and ac voltages, one can cross over from a linear-to a nonlinear-damping dominated regime. We discuss the behavior of the effective quality factor in this context. DOI: 10.1103/PhysRevB.86.23543
The Quantum Hall Effect in Narrow MOSFETs
Contains description of one research project.Joint Services Electronics Program DAAL03-89-C-000
Shot Noise and Full Counting Statistics from Non-equilibrium Plasmons in Luttinger-Liquid Junctions
We consider a quantum wire double junction system with each wire segment
described by a spinless Luttinger model, and study theoretically shot noise in
this system in the sequential tunneling regime. We find that the
non-equilibrium plasmonic excitations in the central wire segment give rise to
qualitatively different behavior compared to the case with equilibrium
plasmons. In particular, shot noise is greatly enhanced by them, and exceeds
the Poisson limit. We show that the enhancement can be explained by the
emergence of several current-carrying processes, and that the effect disappears
if the channels effectively collapse to one due to, {\em e.g.}, fast plasmon
relaxation processes.Comment: 9 pages; IOP Journal style; several changes in the tex
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