Semi-infinite herringbone waveguides in elastic plates

The paper includes novel results for the scattering and localisation of a time-harmonic flexural wave by a semi-infinite herringbone waveguide of rigid pins embedded within an elastic Kirchhoff plate. The analytical model takes into account the orientation and spacing of the constituent parts of the herringbone system, and incorporates dipole approximations for the case of closely spaced pins. Illustrative examples are provided, together with the predictive theoretical analysis of the localised waveforms

ARPES in the normal state of the cuprates: comparing the marginal Fermi liquid and spin fluctuation scenarios

We address the issue whether ARPES measurements of the spectral function $A_k (\omega)$ near the Fermi surface in the normal state of near optimally doped cuprates can distinguish between the marginal Fermi liquid scenario and the spin-fluctuation scenario. We argue that the data for momenta near the Fermi surface are equally well described by both theories, but this agreement is nearly meaningless as in both cases one has to add to $\Sigma^{\prime \prime} (\omega)$ a large constant of yet unknown origin. We show that the data can be well fitted by keeping only this constant term in the self-energy. To distinguish between the two scenarios, one has to analyze the data away from the Fermi surface, when the intrinsic piece in $\Sigma (\omega)$ becomes dominant.Comment: Accepted for publication in Europhysics Letters, Incorrect interpretation of reference 10 correcte

Observation of the second harmonic in superconducting current-phase relation of Nb/Au/(001)YBa2Cu3Ox heterojunctions

The superconducting current-phase relation (CPR) of Nb/Au/(001)YBa2Cu3Ox heterojunctions prepared on epitaxial c-axis oriented YBa2Cu3Ox thin films has been measured in a single-junction interferometer. For the first time, the second harmonic of the CPR of such junctions has been observed. The appearance of the second harmonic and the relative sign of the first and second harmonics of the CPR can be explained assuming, that the macroscopic pairing symmetry of our YBa2Cu3Ox thin films is of the d+s typeComment: 11 pages, 4 figure

Condensation energy in strongly coupled superconductors

We consider the condensation energy in superconductors where the pairing is electronic in origin and is mediated by a collective bosonic mode. We use magnetically-mediated superconductivity as an example, and show that for large spin-fermion couplings, the physics is qualitatively different from the BCS theory as the condensation energy results from the feedback on spin excitations, while the electronic contribution to the condensation energy is positive due to an ``undressing'' feedback on the fermions. The same feedback effect accounts for the gain of the kinetic energy at strong couplings.Comment: 4 pages, revtex 4, 3 eps figure

Anomalous specific heat jump in the heavy fermion superconductor CeCoIn5_5

We study the anomalously large specific heat jump and its systematic change with pressure in CeCoIn$_5$ superconductor. Starting with the general free energy functional of the superconductor for a coupled electron boson system, we derived the analytic result of the specific heat jump of the strong coupling superconductivity occurring in the coupled electron boson system. Then using the two component spin-fermion model we calculate the specific heat coefficient $C(T)/T$ both for the normal and superconducting states and show a good agreement with the experiment of CeCoIn$_5$. Our result also clearly demonstrated that the specific heat coefficient $C(T)/T$ of a coupled electron boson system can be freely interpreted as a renormalization either of the electronic or of the bosonic degrees of freedom.Comment: 5 pages, 2 figure

Two-Particle Interference with Double Twin-Atom Beams

We demonstrate a source for correlated pairs of atoms characterized by two opposite momenta and two spatial modes forming a Bell state only involving external degrees of freedom. We characterize the state of the emitted atom beams by observing strong number squeezing up to -10 dB in the correlated two-particle modes of emission. We furthermore demonstrate genuine two-particle interference in the normalized second-order correlation function $g^{(2)}$ relative to the emitted atoms.Comment: 6 pages, 3 figure

Elastic shear wave scattering by randomly rough surfaces

Characterizing cracks within elastic media forms an important aspect of ultrasonic non-destructive evaluation (NDE) where techniques such as time-of-flight diffraction and pulse-echo are often used with the presumption of scattering from smooth, straight cracks. However, cracks are rarely straight, or smooth, and recent attention has focussed upon rough surface scattering primarily by longitudinal wave excitations. We provide a comprehensive study of scattering by incident shear waves, thus far neglected in models of rough surface scattering despite their practical importance in the detection of surface-breaking defects, using modelling, simulation and supporting experiments. The scattering of incident shear waves introduces challenges, largely absent in the longitudinal case, related to surface wave mode-conversion, the reduced range of validity of the Kirchhoff approximation (KA) as compared with longitudinal incidence, and an increased importance of correlation length. The expected reflection from a rough defect is predicted using a statistical model from which, given the angle of incidence and two statistical parameters, the expected reflection amplitude is obtained instantaneously for any scattering angle and length of defect. If the ratio of correlation length to defect length exceeds a critical value, which we determine, there is an explicit dependence of the scattering results on correlation length, and we modify the modelling to find this dependence. The modelling is cross-correlated against Monte Carlo simulations of many different surface profiles, sharing the same statistical parameter values, using numerical simulation via ray models (KA) and finite element (FE) methods accelerated with a GPU implementation. Additionally we provide experimental validations that demonstrate the accuracy of our predictions

Singularities in the optical response of cuprates

We argue that the detailed analysis of the optical response in cuprate superconductors allows one to verify the magnetic scenario of superconductivity in cuprates, as for strong coupling charge carriers to antiferromagnetic spin fluctuations, the second derivative of optical conductivity should contain detectable singularities at $2\Delta +\Delta_{\rm spin}$, $4\Delta$, and $2\Delta+2\Delta_{\rm spin}$, where $\Delta$ is the amplitude of the superconducting gap, and $\Delta_{s}$ is the resonance energy of spin fluctuations measured in neutron scattering. We argue that there is a good chance that these singularities have already been detected in the experiments on optimally doped $YBCO$.Comment: 6 pages, 4 figure