Surface Plasmons and Topological Insulators

We study surface plasmons localized on interfaces between topologically trivial and topologically non-trivial time reversal invariant materials in three dimensions. For the interface between a metal and a topological insulator the magnetic polarization of the surface plasmon is rotated out of the plane of the interface; this effect should be experimentally observable by exciting the surface plasmon with polarized light. More interestingly, we argue that the same effect also is realized on the interface between vacuum and a doped topological insulator with non-vanishing bulk carrier density.Comment: 6 pages, 1 figure; v2: typo in eq. (27) correcte

Spaser Action, Loss Compensation, and Stability in Plasmonic Systems with Gain

We demonstrate that the conditions of spaser generation and the full loss compensation in a resonant plasmonic-gain medium (metamaterial) are identical. Consequently, attempting the full compensation or overcompensation of losses by gain will lead to instability and a transition to a spaser state. This will limit (clamp) the inversion and lead to the limitation on the maximum loss compensation achievable. The criterion of the loss overcompensation, leading to the instability and spasing, is given in a analytical and universal (independent from system's geometry) form.Comment: 4 pages, 1 figur

Reply to "Can gravitational dynamics be obtained by diffeomorphism invariance of action?"

In a previous work we showed that, in a suitable setting, one can use diffeomorphism invariance in order to derive gravitational field equations from boundary terms of the gravitational action. Standing by our results we reply here to a recent comment questioning their validity.Comment: Accepted for publication in PR

Ad- and desorption of Rb atoms on a gold nanofilm measured by surface plasmon polaritons

Hybrid quantum systems made of cold atoms near nanostructured surfaces are expected to open up new opportunities for the construction of quantum sensors and for quantum information. For the design of such tailored quantum systems the interaction of alkali atoms with dielectric and metallic surfaces is crucial and required to be understood in detail. Here, we present real-time measurements of the adsorption and desorption of Rubidium atoms on gold nanofilms. Surface plasmon polaritons (SPP) are excited at the gold surface and detected in a phase sensitive way. From the temporal change of the SPP phase the Rubidium coverage of the gold film is deduced with a sensitivity of better than 0.3 % of a monolayer. By comparing the experimental data with a Langmuir type adsorption model we obtain the thermal desorption rate and the sticking probability. In addition, also laser-induced desorption is observed and quantified.Comment: 9 pages, 6 figure

Performance analysis of higher mode spoof surface plasmon polariton for terahertz sensing

We investigated the spoof surface plasmon polaritons (SSPPs) on 1D grooved metal surface for terahertz sensing of refractive index of the filling analyte through a prism-coupling attenuated total reflection setup. From the dispersion relation analysis and the finite element method-based simulation, we revealed that the dispersion curve of SSPP got suppressed as the filling refractive index increased, which cause the coupling resonance frequency redshifting in the reflection spectrum. The simulated results for testing various refractive indexes demonstrated that the incident angle of terahertz radiation has a great effect on the performance of sensing. Smaller incident angle will result in a higher sensitive sensing with a narrower detection range. In the meanwhile, the higher order mode SSPP-based sensing has a higher sensitivity with a narrower detection range. The maximum sensitivity is 2.57 THz/RIU for the second-order mode sensing at 45° internal incident angle. The proposed SSPP-based method has great potential for high sensitive terahertz sensing

Surface plasmon resonance imaging detection of silver nanoparticle-tagged immunoglobulin

This article is available open access through the publisher’s website at the link below. Copyright @ 2011 The Royal Society.The detection sensitivity of silver nanoparticle (AgNP)-tagged goat immunoglobulin G (gIgG) microarrays was investigated by studying surface plasmon resonance (SPR) images captured in the visible wavelength range with the help of a Kretchmann-configured optical coupling set-up. The functionalization of anti-gIgG molecules on the AgNP surface was studied using transmission electron microscopy, photon correlation measurements and UV–visible absorption spectroscopy. A value of 1.3 × 107 M−1 was obtained for the antibody–antigen binding constant by monitoring the binding events at a particular resonance wavelength. The detection limit of this SPR imaging instrument is 6.66 nM of gIgG achieved through signal enhancement by a factor of larger than 4 owing to nanoparticle tagging with the antibody.The European Commissio

Emission of light through thin silver films via near-field coupling to surface plasmon polaritons

Copyright © 2006 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Applied Physics Letters 88 (2006) and may be found at http://link.aip.org/link/?APPLAB/88/051109/1We show that the emission of light from a dye layer through an adjacent thin silver film is maximal for a silver thickness of approximately 50 nm. This effect is explained as the result of competition between enhancement of the electric field at the metal surface due to the excitation of a surface plasmon-polariton mode, the amount of power coupled to the surface plasmon-polariton mode, and the attenuation of the field transmitted through the silver, all three of which vary with metal thickness. We indicate how these findings may be of relevance in the design of some surface plasmon-polariton-based fluorescence biosensing schemes

Otto-coupled surface plasmons in a liquid crystal cell

Copyright © 2009 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Applied Physics Letters 95 (2009) and may be found at http://link.aip.org/link/?APPLAB/95/171102/1Surface plasmons on silver in the visible domain are excited using a several micron thick layer of liquid crystal as the optical tunnel barrier. This thickness is possible when the orientation of the director in the liquid crystal varies from homeotropic at the entrance surface (against the coupling prism) to homogeneous on the thick silver layer at the other side of the cell, with the director tilting in a plane normal to the plane of incidence. This geometry also allows the excitation of guided modes, which mixes with the surface plasmon resonance. Both types of mode are then explored as a function of applied voltage

TransverseDiff gravity is to scalar-tensor as unimodular gravity is to General Relativity

Transverse Diffeomorphism (TDiff) theories are well-motivated theories of gravity from the quantum perspective, which are based upon a gauge symmetry principle. The main contribution of this work is to firmly establish a correspondence between TransverseDiff and the better-known scalar-tensor gravity --- in its more general form ---, a relation which is completely analogous to that between unimodular gravity and General Relativity. We then comment on observational aspects of TDiff. In connection with this proof, we derive a very general rule that determines under what conditions the procedure of fixing a gauge symmetry can be equivalently applied before the variational principle leading to the equations of motion, as opposed to the standard procedure, which takes place afterwards; this rule applies to gauge-fixing terms without derivatives.Comment: 10 pages; amsart style; v3: version as appeared in JCAP, redaction improve

Lucky Cars and the Quicksort Algorithm

Quicksort is a classical divide-and-conquer sorting algorithm. It is a comparison sort that makes an average of $2(n+1)H_n - 4n$ comparisons on an array of size $n$ ordered uniformly at random, where $H_n = \sum_{i=1}^n\frac{1}{i}$ is the $n$th harmonic number. Therefore, it makes $n!\left[2(n+1)H_n - 4n\right]$ comparisons to sort all possible orderings of the array. In this article, we prove that this count also enumerates the parking preference lists of $n$ cars parking on a one-way street with $n$ parking spots resulting in exactly $n-1$ lucky cars (i.e., cars that park in their preferred spot). For $n\geq 2$, both counts satisfy the second order recurrence relation $f_n=2nf_{n-1}-n(n-1)f_{n-2}+2(n-1)!$ with $f_0=f_1=0$.Comment: 8 pages, and 2 figures, to appear in The American Mathematical Monthl