ABSTRACT
The most significant goal of nanophotonics is the development of high-speed quantum emitting devices operating at ambient temperature. In this regard, plasmonic nanoparticles-on-mirror are potential candidates for designing high-speed photon sources. We introduce a novel hybrid nanoantenna (HNA) with CdSe/CdS colloidal quantum dots (QDs) based on a silver nanocube in a metal cup that presents a nanoparticle-in-cavity coupled with an emitters system. We use focused ion beam nanolithography to fabricate an ordered array of cups, which were then filled with colloidal nanoparticles using the most simple drop-casting and spin coating methods. The spectral and time-resolved studies of the samples with one or more nanocubes in the cup reveal a significant change in the radiation characteristics of QDs inside the nanoantenna. The Purcell effect causes an increase in the fluorescence decay rate (≥30) and an increase in the fluorescence intensity (≥3) of emitters in the HNA. Using the finite element method simulations, we have discovered that the proximity of the cups wall affects the oscillation modes of the gap plasmon, which, in turn, leads to changes in the electric field enhancement inside the nanoantenna gap. Additionally, substantial variations in the behavior of the gap plasmons at different polarizations of the exciting radiation have been revealed. The proposed nanoantenna can be useful in the development of plasmonic sensors, display pixels, and single-photon sources.
ABSTRACT
There are two types of intrinsic surface states in solids. The first type is formed on the surface of topological insulators. Recently, transport of massless Dirac fermions in the band of "topological" states has been demonstrated. States of the second type were predicted by Tamm and Shockley long ago. They do not have a topological background and are therefore strongly dependent on the properties of the surface. We study the problem of the conductivity of Tamm-Shockley edge states through direct transport experiments. Aharonov-Bohm magneto-oscillations of resistance are found on graphene samples that contain a single nanohole. The effect is explained by the conductivity of the massless Dirac fermions in the edge states cycling around the nanohole. The results demonstrate the deep connection between topological and non-topological edge states in 2D systems of massless Dirac fermions.
ABSTRACT
The radiation inactivation technique was applied to conduct the study on catalytic activity changes of creatine kinase species isolated from the Mid-Asian Death Adder venom. Both intact and the 25Mg-enriched enzyme samples were separately tested. Some differences in radiation stability levels were found to be indicating to a shift in conformational condition (a so called "conformational distribution") of the native enzyme that had happen in the presence of the magnetic nuclei excess.
Subject(s)
Creatine Kinase/chemistry , Creatine Kinase/radiation effects , Magnesium/chemistry , Viper Venoms/enzymology , Animals , Catalysis/radiation effects , Protein Conformation/radiation effects , Radioisotopes/chemistryABSTRACT
Tunneling spectra of chain materials NbSe3 and TaS3 were studied in nanoscale mesa devices. Current-voltage I-V characteristics related to all charge density waves (CDWs) reveal universal spectra within the normally forbidden region of low V, below the electronic CDW gap 2Delta. The tunneling always demonstrates a threshold Vt approximately 0.2Delta, followed, for both CDWs in NbSe3, by a staircase fine structure. T dependencies of Vt(T) and Delta(T) scale together for each CDW, while the low T values Vt(0) correlate with the CDWs' transition temperatures Tp. Fine structures of CDWs perfectly coincide when scaled along V/Delta. The results evidence the sequential entering of CDW vortices (dislocations) in the junction area with the tunneling current concentrated in their cores. The subgap tunneling proceeds via the phase channel: coherent phase slips at neighboring chains.
ABSTRACT
We report on direct observation of microscopic solitons in single electronic processes of the coherent interlayer tunneling in charge density waves. Special nanoscale devices were fabricated from the chain compound using focused ion beams. The spectra were drastically refined by working at high (up to 27 T) magnetic fields. Internal quantum tunneling of electrons can go through solitons that are energetically more favorable quantum particles than electrons. In addition to the interband tunneling across the gap 2Delta, we observe a clear peak at the intermediate voltage approximately 2Delta/3, which we associate with the creation of microscopic solitons, the energy of which must be 2Delta/pi. These solitons might correspond to the long sought special quasiparticle--the spinon.
ABSTRACT
Central hemodynamic parameters were assessed by tetrapolar chest rheography during rationed isometric pedal stress exposure in 54 normal subjects and 24 angina patients. The relationship between left-ventricular contractility and the magnitude of increasing static effort at different steps of stress exposure was examined. In normal subjects, the increase in static effort was shown to affect significantly left-ventricular contractile capacity, left-ventricular performance index and left-ventricular contractile index, and has no effect on the myocardial contractility index. In anginal patients, developing myocardial ischemia in response to stress, there was a significant drop in left-ventricular contraction intensity, myocardial contractility index and left-ventricular contractile index, as compared to the pre-ischemic values. The rheographic left-ventricular contractile index is believed to be the best instrument for the assessment of left-ventricular inotropic activity in isometric stress.