Klaus Halterman

Coherent perfect absorption in epsilon-near-zero metamaterials

Above-light-line surface plasmon polaritons can arise at t he interface between a metal and ǫ-near-zero metamaterial. This unique feature induces unusual fast-wave no n-radiative modes in aǫ-near-zero material/metal bilayer. Excitation of this peculiar mode leads to wide-ang le perfect absorption in low-loss ultrathin metamaterials. The ratio of the perfect absorption wavelength to t he thickness of theǫ-near-zero metamaterial can be as high as 10 4; the electromagnetic energy can be confined in a layer as thin asλ/10000. Unlike conventional fast-wave leaky modes, these fast-wave non-radiative mode s have quasi-static capacitive features that naturally match with the space-wave field, and thus are easily accessib l from free space. The perfect absorption wavelength can be tuned from midto far-infrared by tuning the ǫ ≈ 0 wavelength while keeping the thickness of the structure unchanged.

Proximity effects and characteristic lengths in ferromagnet-superconductor structures

We present an extensive theoretical investigation of the proximity effects that occur in clean ferromagnet/ superconductor (F/S) systems. We use a numerical method to solve self-consistently the Bogoliubov-de Gennes equations in the continuum. We obtain the pair amplitude and the local density of states, and use these results to extract the relevant lengths characterizing the leakage of superconductivity into the magnet and to study spin splitting into the superconductor. These phenomena are investigated as a function of parameters such as temperature, magnet polarization, interfacial scattering, sample size and Fermi wave vector mismatch, all of which turn out to have important influence on the results. These results should help characterize and analyze future data and are shown to be in agreement with existing experiments.

Proximity effects at ferromagnet-superconductor interfaces

We study proximity effects at ferromagnet-superconductor interfaces by self-consistent numerical solution of the Bogoliubov-de Gennes equations for the continuum, without any approximations. Our procedures allow us to study systems with long superconducting coherence lengths. We obtain results for the pair potential, the pair amplitude, and the local density of states. We use these results to extract the relevant proximity lengths. We find that the superconducting correlations in the ferromagnet exhibit a damped oscillatory behavior that is reflected in both the pair amplitude and the local density of states. The characteristic length scale of these oscillations is approximately inversely proportional to the exchange field, and is independent of the superconducting coherence length in the range studied. We find the superconducting coherence length to be nearly independent of the ferromagnetic polarization.

Odd triplet pairing in clean superconductor/ferromagnet heterostructures

We study triplet pairing correlations in clean ferromagnet (F)/superconductor (S) nanojunctions, via fully self-consistent solution of the Bogoliubov-de Gennes equations. We consider FSF trilayers, with S being an s-wave superconductor, and an arbitrary angle alpha between the magnetizations of the two F layers. We find that contrary to some previous expectations, triplet correlations, odd in time, are induced in both the S and F layers in the clean limit. We investigate their behavior as a function of time, position, and alpha. The triplet amplitudes are largest at times on the order of the inverse Debye frequency, and at that time scale they are long-ranged in both S and F. The zero temperature condensation energy is found to be lowest when the magnetizations are antiparallel.

Plasmonic resonances and electromagnetic forces between coupled silver nanowires

We compute the electromagnetic response and corresponding forces between two silver nanowires. The wires are illuminated by a plane wave which has the electric field vector perpendicular to the axis of the wires, insuring that plasmonic resonances can be excited. We consider a nontrivial square cross section geometry that has dimensions on the order of

Discrete Cylindrical Vector Beam Generation from an Array of Optical Fibers

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Angular dependence of the superconducting transition temperature in ferromagnet-superconductor-ferromagnet trilayers

, where

Induced triplet pairing in clean s -wave superconductor/ferromagnet layered structures

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Angular dependence of superconductivity in superconductor/spin-valve heterostructures

is the wavelength of the incident electromagnetic field. We find that due to the plasmonic resonance, there occurs great enhancement of the direct and mutual electromagnetic forces that are exerted on the nanowires. The Lippman-Schwinger volume integral equation is implemented to obtain solutions to Maxwells equations for various

Parametrically shielding electromagnetic fields by nonlinear metamaterials.

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