[en] The first direct measurements of the dissipation due to flow are performed and the effects of that flow on the NMR properties of ³He-A are studied. A temperature-independent critical velocity v/sub c/=0.52 mm/s is observed, above which a pressure difference proportional to v/sub s/-v/sub c/ developes across our flow orifice. simultaneously, the NMR frequency in ³He-A is lowered by an amount also proportional to v/sub s/-v/sub c/, in contrast to current theoretical predictions

[en] Transverse cw NMR measurements on the superfluid phases of ³He are reported for temperatures between 3 and 0.7 mK. Nuclear demagnetization of copper was used for refrigeration. For thermometry, pulsed NMR was used on platinum powder immersed in the liquid. The measurements on ³He were carried out in two NMR coil assemblies in which the liquid was confined between parallel Mylar foils with separations of 0.37 mm and 4 μm. The transition temperature T/sub c/ was measured at pressures between 32 bars and the saturated vapor pressure; a pressure-independent increase of approximately 11 percent was observed in T/sub c/ with respect to earlier data obtained with the same apparatus. In the 4-μm stack a reduction in the B → A transition temperature was observed. In measurements on the orientational anisotropy of the B phase, qualitative agreement with the theory of Brinkman et al. was found. The longitudinal resonance frequencies of the A and B phases were measured between 32 bars and the polycritical point. In the 4-μm stack a negative NMR shift was found in the A phase when the field was oriented perpendicular to the Mylar plates, in agreement with the prediction of Takagi. The static susceptibility chi/sub B/ of the B phase was measured as a function of temperature at 18.7 and 29 bars; its low-temperature limiting value was observed to be (0.33 +- 0.02)chi/sub N/, independent of pressure. The strong coupling corrections to the size of the energy gap were estimated. The initial slope of the reduced gap in the A phase, Δ/sub A//T/sub c/, was found to increase by approximately 25 percent when the pressure increased from 21.1 bars to the melting curve, whereas in the low-temperature limit Δ/sub B/(0)/T/sub c/ was found to be independent of pressure and close to its weak coupling value

[en] The second-sound velocity of three dilute ³He-⁴He mixtures was measured with high precision down to a temperature of 10 mK and in a magnetic field of 93 kOe. For the most dilute sample, which had a molar concentration of 0.001, the maximum spin polarization of the ³He atoms was estimated to be 36%. The measured relative change in the second-sound velocity was 3%. This is considerably larger than the change predicted recently by Bashkin and Meyerovich. An explanation for this discrepancy is presented

[en] A Comment on the Letter by Pyun and Lemberger, Phys. Rev. 63, 2132 (1989)

[en] The relative changes in the low-temperature susceptibility of a number of dilute mixtures of ³He in liquid ⁴He at various pressures are reported and analyzed. Under elevated pressures, the solubility of ³He in ⁴He increases and the effects of the interaction between ³He quasiparticles clearly become larger. However, no evidence of a BCS pairing transition was found in direct measurements of susceptibility and nuclear resonance frequency down to the temperature 1.5 mK in saturated solutions with a pressure of 21 bar

[en] Recent experimental and theoretical work on the metal-insulator transition in phosphorous doped silicon (Si:P) is reviewed. Selected transport and thermodynamic properties of uncompensated and compensated samples are compared with the predictions of the scaling theory of localization and with the local moment theory. The implications for the breakdown of Landau's Fermi-liquid theory are discussed. (orig.)

[en] We have measured the moment of inertia of hcp ⁴He crystals from 25 mK to 2 K. With a precision of five parts in 10⁶ we find no evidence for a nonclassical rotational inertia. This indicates that if a supersolid exists, it has a rho/sub s//rho of less than 5 x 10^-6, a transition temperature of less than 25 mK, or a critical velocity of less than 5 μm/sec

[en] Textural defects in the A phase are created in a slab geometry by an RF pulse and are stable in magnetic fields. The defects are observed as holes in NMR absorption signals with a field gradient and as a satellite peak in a homogeneous field. In order to create such defects, both the amplitude and the length of the RF pulse have to be larger than well defined thresholds. (author)

[en] The characteristic lengths associated with the flux-flow resistance and critical fields measured at the vortex-antivortex transition temperature of thin-film InInO/sub x/ composites have been found to be approximately equal and to diverge simultaneously near critical disorder where superconductivity disappears. The observed disorder-induced enhancement of the vortex mobility cannot be explained by the dirty-limit formula for the coherence length when used within the context of the Bardeen-Stephen description for vortex dissipation

[en] A procedure is described by which the temperature-dependent upper critical field H/sub c/2(T) in highly disordered thin-film superconductors with broad resistive transitions is determined. Resistance versus perpendicular magnetic field isotherms are used in conjunction with the mean field transition temperature T/sub c/ 0, derived from Aslamazov--Larkin fits to the zero-field resistive transition, to determine H/sub c/2(T). The sensitivity of the slope parameter (dH/sub c/2/dT)Vertical Bar/sub T//sub c/ 0 with respect to the details of the procedure is discussed and the conditions under which meaningful comparisons with theory can be made are elaborated