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In this work we present resonant inelastic light scattering (Raman) studies of individual tubes suspended in air. Using high resolution micro-Raman spectroscopy with tunable filters for high throughput we have mapped the resonance Raman profiles for a series of individual SWNTs in the 2n+m = 22 and 29 families and found clear evidence of excitonic interactions from the Raman measurements. Individual suspended SWNTs are grown across etched trenches on a quartz substrate with the chemical vapor deposition technique. For a single suspended tube, the laser excitation energy is tuned to find the electronic resonance, indicated by an intensity maximum of the Raman radial breathing mode (RBM). The Stokes and anti-Stokes double-peaks are offset in energy as expected from incoming and outgoing light resonance with the electronic level. It is demonstrated that the double peaks in the resonance window are separated by the RBM phonon energy, determining the width of the resonance profile

The application of a new superconducting composite wire developed by C.C. Tsuei for high-field, high-current uses is explored. The importance of the dish continuous nature of the superconducting filaments in this material is analyzed. Our calculations indicate that practical wire may have a remnant resistivity of 10-14ohm-cm or less and we report our experiments to date in which we have tried to measure this quantity. We also report our observations of quantum coupling between filaments in this wire.

We have observed an anomalous decrease of the measured Josephson critical current as temperature is decreased below 0.85T/sub c/ on small Sn-SnOx-Sn tunnel junctions. The results of analog and dig- ital simulations over a wide range of junction noise and damping parameters suggest that this anomalous temperature dependence of the critical current could be caused by the strongly temperature-dependent damping effect of the quasiparticle tunnel resistance below the gap voltage.

We have measured the change in the thermal conductivity of superconducting tin, indium, and lead films upon application of a magnetic field in the plane of the film. These experiments were undertaken to explore the dependence of the energy gap upon magnetic field and to determine the thermodynamic order of the field-induced transition in films. Within the range of temperatures available to us ($0.35{T}_{c}$ to $0.65{T}_{c}$) the thermal conductivity of indium and tin films increases nearly as ${H}^{2}$. In films of thickness $d\ensuremath{\geqq}2800$ \AA{} the thermal conductivity jumps at ${H}_{c}$ to the normal state value, indicating a first-order phase transition in thin films, consistent with the Ginzburg-Landau (GL) theory. If the effect of a field upon the superconducting state can be adequately represented as a change of the ${\ensuremath{\epsilon}}_{0}$ of BCS, we may use the theory of Bardeen, Rickayzen, and Tewordt to compute ${\ensuremath{\epsilon}}_{0}(H)$ from our data. At $T=0.65{T}_{c}$ we find $\frac{{\ensuremath{\epsilon}}_{0}(H)}{{\ensuremath{\epsilon}}_{0}(H=0)}={[1\ensuremath{-}{(\frac{H}{{H}_{c}})}^{2}]}^{\frac{1}{2}}$ in agreement with the GL prediction. At $T=0.35{T}_{c}$ however, $\frac{{\ensuremath{\epsilon}}_{0}(H)}{{\ensuremath{\epsilon}}_{0}(0)}=1\ensuremath{-}{(\frac{H}{{H}_{c}})}^{2}$ provides a more satisfactory fit to our data. Orientation of the field \ensuremath{\perp} and \ensuremath{\parallel} to the direction of heat flow produces the same effect on the thermal conductivity to \ifmmode\pm\else\textpm\fi{}1%. This is interesting in view of Bogoliubov's prediction of a ${\mathrm{p}}_{F}\ifmmode\cdot\else\textperiodcentered\fi{}{\mathrm{v}}_{\mathrm{drift}}$ term in the excitation spectrum of a current-carrying superconductor. When the field is not parallel to the surface of the film the thermodynamic transition is still sharply defined, but ${H}_{c}$ is reduced. Thin lead films gave results similar to those of indium and tin films except that at low fields the field-dependent conductivity increased more slowly than ${H}^{2}$ at low temperatures.

Polarized reflection spectra have been made of single crystal KH2PO4, TGS, TiO2, and KD2PO4. KH2PO4 and TiO2 were studied in the range 2.5 to 1500 cm—1, TGS and KD2PO4 over a somewhat smaller range. The reflectivity data were analyzed using dispersion theory and classical‐oscillator fits to obtain the optical constants. The hydrogen bonded ferroelectrics show a behavior quite different from the perovskite ferroelectrics studied earlier. A highly overdamped ferroelectric mode is found in KH2PO4 near 50 cm—1 at room temperature. The close similarities of certain modes in KH2PO4 and KD2PO4 do not support previous speculations on proton tunneling. An analysis of the mode strengths in TGS shows that the major dispersion which contributes to the low‐frequency dielectric constant takes place below 14 cm—1. TiO2 exhibits strong modes near 190 cm—1 which are connected with its large value of low‐frequency dielectric constant, and are quite similar to the low‐frequency mode in SrTiO3.

A rather general relation is derived between vertical accelerations of the train and cryogenic power dissipation due to ac currents induced in the superconducting suspension magnets. Our theoretical results account for the order of magnitude of the rather large losses observed in the Fuji Electric test vehicle, which used less than state‐of‐the‐art conductors. Even with parameters estimated to represent the best commercially available materials, however, it appears that these losses may be comparable with the total heat leak due to all other causes if the accelerations are as large as permitted by subjective human ride quality considerations. Empirical data on losses under appropriate conditions of B, Ḃ, and I/Ic may be needed to ascertain whether improved materials will be required to avoid serious design constraints by cryogenic heating.

Apparatus especially designed for studying electron paramagnetic resonance is described and discussed. A magnet of novel yokeless design is presented. Field stabilization and modulation procedure is considered. The microwave sample cavity is analyzed to determine conditions for optimum operation. The klystron stabilization problem is examined. Appropriate lumped circuits for low‐frequency operation are described. The signal amplification and presentation system is treated in detail.

The usefulness of exciting a single circularly-polarized mode in a microwave cavity is indicated. A matrix method is presented then for the analysis of the operation of various components, such as transition pieces and differential phase shifters on waves propagating in waveguides with two degenerate orthogonal modes. This method is applied to describe three distinct systems for generating the desired circular polarization in a cavity that is coupled directly to the side wall of a waveguide. The final system, which involves a minimum of critical adjustments, is described in more detail, and its performance is indicated. It is shown that purely circular radiation can be set up along the axis of the cavity. However, the largest preponderance of one rotating mode over the other which can be set up, if one averages over the entire cavity volume, is 11.5 to 1. This value is obtained with the TE11n modes.

Tunneling experiments were performed on thin superconducting films in the presence of a magnetic field. The experiments were done at ${\mathrm{He}}^{3}$ temperatures on tin and tin-indium alloy films with thicknesses between 600 and 2000 \AA{}. As expected theoretically, the effect of the field on the density of states is, for dirty films, similar to the effect of paramagnetic impurities with the square of the magnetic field playing a role analogous to the paramagnetic impurity concentration. The data are compared with the theoretical results of Maki for the limit of zero mean free path, and agreement is fair. The difference between these results and those of this experiment is attributed to the finite mean free path. Str\"assler and Wyder have calculated the field dependence of the density of states for small particles with arbitrary mean free path. We find that their calculations are in good agreement with experiment.

The uniaxial dipolar anisotropy in antiferromagnetic MnO and NiO aligns the two opposing sublattice moments in an easy (111) plane. The two normal modes for small oscillations of the sublattice magnetizations about a preferred direction within this plane are both nondegenerate and linearly polarized. The high-frequency mode has been observed at low temperatures (2\ifmmode^\circ\else\textdegree\fi{}K) at 27.5 and 36.6 ${\mathrm{cm}}^{\ensuremath{-}1}$ in MnO and NiO, respectively. In agreement with the unobservably small second-order Zeeman shift expected for these non-degenerate modes, a 10.7-kOe field was found to have no effect on the observed resonance frequencies. Increasing the sample temperature decreases the frequency of the mode in each case. The experimental temperature dependence of the antiferromagnetic resonance frequency can be accounted for by present theories only if an anomalous temperature dependence, previously found from neutron-diffraction data, is assumed for the temperature dependence of the sublattice magnetization.

In situ formed superconducting filamentary composites are of considerable interest from both theoretical and practical points of view. A number of authors1 have demonstrated that these composites can carry critical currents comparable to those of the best conventional conductors with continuous Nb3Sn or V3Ga filaments and they are also remarkably insensitive to mechanical stress or strain. Along with the powder-metallurgically processed composites,2 these new materials show realistic promise for potential practical applications and can now be produced also in large quantities.3

The fundamental processes governing the appearance of dissipation due to flux motion in superconductors are reviewed. The dominant thermally‐activated resistive processes are discussed, and evidence for a sharp melting transition of the flux lattice is assessed.

The magnetic field penetration depth λ of superconductors has been measured in the past by various radiofrequency and microwave techniques or by using small colloidal samples. In this paper we describe a new method, which we have successfully applied to tin, for directly measuring the temperature dependence of λ at dc and on macroscopic, oriented single crystals. The method utilizes the extremely high flux sensitivity of a SQUID magnetometer to measure the flux penetrating into a superconductor in a low (~ 1 Oe) static magnetic field. With this technique changes in λ as small as 2 A can be resolved. Moreover, flat, planar samples have been used so that both the direction of the shielding current J and the normal \(\hat{n}\) to the sample surface can be directed along well-defined crystallographic directions. The temperature dependence of λ is found to depend on both Ĵ and \(\hat{n}\). While a dependence on Ĵ has been observed previously, the dependence on \(\hat{n}\) has not. As described below, both types of anisotropy can be understood on the basis of Pippard’s nonlocal theory1 of electrodynamics.

The fractional transmission of far infrared radiation through metal light pipes is calculated and compared with experimental data. Transmission factors greater than fifty percent are obtained over distances of several feet with typical parameters. Condensing cones allow the output radiation to be concentrated onto a small detector area for spectroscopic applications.