Emergent phases in a compass chain with multisite interactions

We study a dimerised spin chain with biaxial magnetic interacting ions in the presence of an externally induced three-site interactions out of equilibrium. In the general case, the three-site interactions play a role in renormalizing the effective uniform magnetic field. We find that the existence of zero-energy Majorana modes is intricately related to the sign of Pfaffian of the Bogoliubov-de Gennes Hamiltonian and the relevant $Z_2$ topological invariant. In contrast, we show that an exotic spin liquid phase can emerge in the compass limit through a Berezinskii-Kosterlitz-Thouless (BKT) quantum phase transition. Such a BKT transition is characterized by a large dynamic exponent $z=4$, and the spin-liquid phase is robust under a uniform magnetic field. We find the relative entropy and the quantum discord can signal the BKT transitions. We also uncover a few differences in deriving the correlation functions for the systems with broken reflection symmetry.Comment: 12 pages, 10 figure

Identification of the optimal spectral region for plasmonic and nanoplasmonic sensing

This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in ACS Nano, copyright © American Chemical Society after peer review. To access the final edited and published work see http://pubs.acs.org/articlesonrequest/AOR-jfCkKFwsJwtEYkHTFzG7We present a theoretical and experimental study involving the sensing characteristics of wavelength interrogated plasmonic sensors based on Surface Plasmon Polaritons (SPP) in planar gold films and on Localized Surface Plasmon Resonances (LSPR) of single gold nanorods. The tunability of both sensing platforms allowed us to analyze their bulk and surface sensing characteristics as a function of the plasmon resonance position. We demonstrate that a general figure of merit (FOM), which is equivalent in wavelength and energy scales, can be employed to mutually compare both sensing schemes. Most interestingly, this FOM has revealed a spectral region for which the surface sensitivity performance of both sensor types is optimized, which we attribute to the intrinsic dielectric properties of plasmonic materials. Additionally, in good agreement with theoretical predictions, we experimentally demonstrate that, although the SPP sensor offers a much better bulk sensitivity, the LSPR sensor shows an approximately 15% better performance for surface sensitivity measurements when its FOM is optimized. However, optimization of the substrate refractive index and the accessibility of the relevant molecules to the nanoparticles can lead to a total 3-fold improvement of the FOM in LSPR sensors.This research was carried out with the support of the Commission for Universities and Investigation belonging to the Department of Innovation, Universities and Companies of the Generalitat de Catalunya, and the Social European Fund. Financial support of the M. Botn Foundation and the Nanomag CIBER-BBN Project is also greatly acknowledged. L.M.L.-M. acknowledges financial support from Ministerio de Ciencia e Innovacin (MAT2007-62696 and PCI2005-A7-0075).Peer reviewe

Effects of Dyes, Gold Nanocrystals, pH, and Metal Ions on Plasmonic and Molecular Resonance Coupling

The effects of various factors on the resonance coupling between elongated Au nanocrystals and organic dyes have been systematically investigated through the preparation of hybrid nanostructures between Au nanocrystals and the electrostatically adsorbed dye molecules. A nanocrystal sample is chosen for each dye to match the longitudinal plasmon resonance wavelength with the absorption peak wavelength of the dye as close as possible so that the resonance coupling strength can be maximized. The resonance coupling strength is found to approximately increase as the molecular volume-normalized absorptivity is increased. It is mainly determined by the plasmon resonance energy of the Au nanocrystals instead of their shapes and sizes. Moreover, the resonance coupling can be reversibly controlled if the dye in the hybrid nanostructures is pH-sensitive. The coupling can also be weakened in the presence of metal ions. These results will be highly useful for designing resonance coupling-based sensing devices and for plasmon-enhanced spectroscopy

A General Approach to the Synthesis of Gold-Metal Sulfide Core-Shell and Heterostructures

Cores and effect: Water-dispersible core-shell structures and heterostructures incorporating gold nanocrystals of different shapes (polyhedra, cubes, and rods) and a variety of transition metal sulfide semiconductors (ZnS, CdS, NiS, Ag₂S, and CuS) are synthesized using cetyltrimethylammonium bromide-encapsulated gold nanocrystals and metal thiobenzoates as starting materials. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA

Comparison of the clinical outcomes of two physiological ischemic training methods in patients with coronary heart disease

The aim of the present study was to verify the effectiveness of physiological ischemic training (PIT) in patients with coronary heart disease (CHD) and compare differences in clinical outcomes between isometric exercise training (IET) and cuff inflation training (CIT)

Evidence for Hydrogen-Bonding-Directed Assembly of Gold Nanorods in Aqueous Solution

We report experimental and theoretical demonstration regarding the hydrogen-bonding mechanism behind the end-to-end assembly of gold nanorods modified with bifunctional linking molecules. Time-dependent assembly studies were carried out for different linking molecules at both higher and lower pH values with respect to their respective p<i>K</i>_a values and were all found to be in agreement with a hydrogen-bonding theory. The results indicate that hydrogen bonding between protonated and unprotonated linking molecules is responsible for nanorod assembly in aqueous solution. Complementary information regarding the stability of the hydrogen-bonded configurations was obtained by density functional calculations for different protonation states