Singular current response from isolated impurities in d-wave superconductors

The current response of a d-wave superconductor containing a single impurity is calculated and shown to be singular in the low-temperature limit, leading in the case of strong scattering to a 1/T term in the penetration depth $\lambda(T)$ similar to that induced by Andreev surface bound states. For a small number of such impurities, we argue this low-$T$ upturn could be observable in cuprate superconductors.Comment: 4 pages, 2 .eps figures. Minor changes to match the published versio

Unconventional Spin Density Waves in Dipolar Fermi Gases

The conventional spin density wave (SDW) phase (Overhauser, 1962), as found in antiferromagnetic metal for example (Fawcett 1988), can be described as a condensate of particle-hole pairs with zero angular momentum, $\ell=0$, analogous to a condensate of particle-particle pairs in conventional superconductors. While many unconventional superconductors with Cooper pairs of finite $\ell$ have been discovered, their counterparts, density waves with non-zero angular momenta, have only been hypothesized in two-dimensional electron systems (Nayak, 2000). Using an unbiased functional renormalization group analysis, we here show that spin-triplet particle-hole condensates with $\ell=1$ emerge generically in dipolar Fermi gases of atoms (Lu, Burdick, and Lev, 2012) or molecules (Ospelkaus et al., 2008; Wu et al.) on optical lattice. The order parameter of these exotic SDWs is a vector quantity in spin space, and, moreover, is defined on lattice bonds rather than on lattice sites. We determine the rich quantum phase diagram of dipolar fermions at half-filling as a function of the dipolar orientation, and discuss how these SDWs arise amidst competition with superfluid and charge density wave phases.Comment: 5 pages, 3 figure

Quantized vortices in a rotating Bose-Einstein condensate with spatiotemporally modulated interaction

We present theoretical analysis and numerical studies of the quantized vortices in a rotating Bose-Einstein condensate with spatiotemporally modulated interaction in harmonic and anharmonic potentials, respectively. The exact quantized vortex and giant vortex solutions are constructed explicitly by similarity transformation. Their stability behavior has been examined by numerical simulation, which shows that a new series of stable vortex states (defined by radial and angular quantum numbers) can be supported by the spatiotemporally modulated interaction in this system. We find that there exist stable quantized vortices with large topological charges in repulsive condensates with spatiotemporally modulated interaction. We also give an experimental protocol to observe these vortex states in future experiments

An Introduction to the Digital Watermarking

Digital watermarking is the process of embedding a message pertaining to the digital content itself and contains information about its author, buyer etc. It is same as that of steganography; only the difference is in the process of hiding the information. In digital watermarking the information is hided pertaining to the digital content itself whereas the message embedded in a digital content in the case of steganography is the secret message that has to be transmitted over the communication channel. Hence digital watermarking can be used for many applications like ownership assertion, copy right prevention, fingerprinting, data authentication (medical field) etc

New effective interactions in RMF theory with non-linear terms and density-dependent meson-nucleon coupling

New parameter sets for the Lagrangian density in the relativistic mean field (RMF) theory, PK1 with nonlinear sigma- and omega-meson self-coupling, PK1R with nonlinear sigma-, omega- and rho-meson self-coupling and PKDD with the density-dependent meson-nucleon coupling, are proposed. They are able to provide an excellent description not only for the properties of nuclear matter but also for the nuclei in and far from the valley of beta-stability. For the first time in the parametrization of the RMF Lagrangian density, the center-of-mass correction is treated by a microscopic way, which is essential to unify the description of nuclei from light to heavy regions with one effective interaction.Comment: 22 pages, 16 EPS figures, RevTeX

Holographic Superconductor for a Lifshitz fixed point

We consider the gravity dual of strongly coupled system at a Lifshitz-fixed point and finite temperature, which was constructed in a recent work arXiv:0909.0263. We construct an Abelian Higgs model in that background and calculate condensation and conductivity using holographic techniques. We find that condensation happens and DC conductivity blows up when temperature turns below a critical value.Comment: 14 pages, 4 figures, v4: improved version, references adde

Coherent vibrations of submicron spherical gold shells in a photonic crystal

Coherent acoustic radial oscillations of thin spherical gold shells of submicron diameter excited by an ultrashort optical pulse are observed in the form of pronounced modulations of the transient reflectivity on a subnanosecond time scale. Strong acousto-optical coupling in a photonic crystal enhances the modulation of the transient reflectivity up to 4%. The frequency of these oscillations is demonstrated to be in good agreement with Lamb theory of free gold shells.Comment: Error in Eqs.2 and 3 corrected; Tabl. I corrected; Fig.1 revised; a model that explains the dependence of the oscillation amplitude of the transient reflectivity with wavelength adde

Formation of diluted III–V nitride thin films by N ion implantation

iluted III–Nₓ–V₁ˍₓ alloys were successfully synthesized by nitrogen implantation into GaAs,InP, and AlyGa1−yAs. In all three cases the fundamental band-gap energy for the ion beam synthesized III–Nₓ–V₁ˍₓ alloys was found to decrease with increasing N implantation dose in a manner similar to that observed in epitaxially grownGaNₓAs1−x and InNₓP₁ˍₓalloys. In GaNₓAs₁ˍₓ the highest value of x (fraction of “active” substitutional N on As sublattice) achieved was 0.006. It was observed that NAs is thermally unstable at temperatures higher than 850 °C. The highest value of x achieved in InNₓP₁ˍₓ was higher, 0.012, and the NP was found to be stable to at least 850 °C. In addition, the N activation efficiency in implantedInNₓP₁ˍₓ was at least a factor of 2 higher than that in GaNₓAs₁ˍₓ under similar processing conditions. AlyGa1−yNₓAs₁ˍₓ had not been made previously by epitaxial techniques. N implantation was successful in producing AlyGa1−yNₓAs₁ˍₓalloys. Notably, the band gap of these alloys remains direct, even above the value of y (y>0.44) where the band gap of the host material is indirect.This work was supported by the ‘‘Photovoltaic Materials Focus Area’’ in the DOE Center of Excellence for the Synthesis and Processing of Advanced Materials, Office of Science, Office of Basic Energy Sciences, Division of Materials Sciences under U.S. Department of Energy Contract No. DE-ACO3-76SF00098. The work at UCSD was partially supported by Midwest Research Institute under subcontractor No. AAD-9-18668-7 from NREL

Interaction between two non-threshold bound states

A general non-threshold BPS (F, D$_p$) (or (D$_{p - 2}$, D$_p$)) bound state can be described by a boundary state with a quantized world-volume electric (or magnetic) flux and is characterized by a pair of integers $(m, n)$. With this, we calculate explicitly the interaction amplitude between two such non-threshold bound states with a separation $Y$ when each of the states is characterized by a pair of integers ($m_i, n_i$) with $i = 1, 2$. With this result, one can show that the non-degenerate (i.e., $m_i n_i \neq 0$) interaction is in general attractive for the case of (D$_{p - 2}$, D$_p$) but this is true and for certain only at large separation for the case of (F, D$_p$). In either case, this interaction vanishes only if $m_1/ n_1 = m_2/ n_2$ and $n_1 n_2 > 0$. We also study the analytic structure of the corresponding amplitude and calculate in particular the rate of pair production of open strings in the case of (F, D$_p$).Comment: 32 pages, no figures, minor change and one reference adde