bluuebunny/crossref_metadata_2025 huggingface dataset:
Superconductivity in Two-Dimensional Disordered Thin Films
Authors: Beasley M. R.
Published: March 2014

The influence of disorder on the transition temperature of 2D superconducting thin films is reviewed. It is argued that the major origin of the reduction is enhanced Coulomb interactions in these systems, but that a complete understanding of the problem is not yet available.
Propagation of Second Sound in 3He–B Using Peshkov Transducers
Authors: Lu S. T. , Kojima H.
Published: March 2014

The propagation of second sound (entropy wave) was observed In super fluid 3He-B using a resonance method (frequency≈1 Hz) and Peshkov transducers. The Peshkov transducer consisted of a superleak (glass capillary array) and a flexible diaphragm(1 µm thick nickel foil). The measured speed of second sound is in good agreement with the expected value. The second sound propagation could not be observed in the A phase.
Recent Developments in the Study of Superconducting and Normal Metal Networks
Authors: Pannetier B. , Chaussy J. , Rammal R.
Published: March 2014

The observation and the understanding of frustration effects in superconducting networks have promoted extensive studies in this field since 1983. Perhaps the major impact of this subject results from the direct correspondence between the Ginzburg-Landau equation for the superconducting transition and the Schrödinger equation. This duality makes these systems excellent model systems for accurate testing of general properties of the electronic states on artificial lattices. Thees studies have been extended in two directions : measuremnts of fiux quantization in self similar or quasiperiodic networks, investigation of the mixed state and equilibrium magnetization below Tc. Measurements have also been performed on the magnetoresistance of various periodic and non periodic networks in the weak localization regime. Comparison with theoretical prediction based upon the A.A.S. model and its extension by Douçot and Rammal to arbitrary networks, provides a very accuratetest of the weak localization theory in periodic as well as self similar networks. The most recent developments in this field are reviewed, in this paper.
New Textural Phases in 3He–A
Authors: Dow R. C. M. , Lambert C. J.
Published: March 2014

The response of 3He–A textures to imposed superfluid massflow and applied magnetic field is studied by means of numerical integration. Results are presented which indicate the existence of a previously unsuspected textural phase transition under increasing magnetic field in massflows of strength comparable to that of the dipolar interaction. This transition is from a stable dynamic domain-lattice texture to an unstable texture, and is identified by the dramatic change which occurs in the Fourier transform of the time charactristics of the texture. In higher magnetic field a dynamic domain-lattice transverse to the axis of the low field texture becomes the stable textural phase.
Critical Currents in the YBaCuO Compound Superconducting Thin Films
Authors: Chaudhari P.
Published: March 2014

This note contains information on the properties of epitaxial thin films of the high temperature YBaCuO compound superconductors. Some thoughts regarding critical current and mechanisms of vortex pinning are presented. It is suggested that one of the more effective mechanism of pinning is associated with a random distribution of defects which perturb the condensation energy. The defects are on the scale of the coherence length.
Proximity Effect in Bulk and Surface Inversion Layer of InAs and its Application to Superconducting Transistors
Authors: Kawakami Tsuyoshi , Takayanagi Hideaki
Published: March 2014

Superconductivity induced by proximity effect in narrow-gap high-electron-mobility semiconductor InAs and its surface inversion two-dimensional electron gas(2DEG) has been confirmed using Nb-InAs-Nb SNS junctions. It is found that supercurrent through the junctions is strongly dependent on SN interface properties. Carrier concentration and electrode spacing dependences of critical current Ic are obtained. Coherence lengths in n-InAs and surface inversion layer are discussed on the basis of proximity theory. Supercurrent control is realized using three-terminal device operation in field-effect and quasiparticle-injection modes.
Shear-Induced Melting of the 2-D Electron Crystal
Authors: Wilen L. , Giannetta R.
Published: March 2014

We observe a drive dependent phase transition for the 2D electron crystal in a magnetic field. The critical field, B
crit, depends upon pressing electric field, temperature, and drive amplitude. B
Crit→0 as we approach the thermodynamic Wigner transition temperature. The data is analyzed with a simple shearing model from which we infer a yield strength for the electron crystal.
Decomposition Kinetics in Solid Solutions of Helium Isotopes at Superlow Temperatures
Authors: Mikheev V. A. , Maidanov V. A. , Mikhin N. P. , Kal'noy S. E. , Omelaenko N. F.
Published: March 2014

Pulsed NMR method is used to study phase separation kinetics in solid solution of He isotopes with 0.54 % 3He at 100 mK and 20.55 cm3/mole. The growth of 3He-enriched phase continued more than 30 hr with rate and separation temperature depending on sample history. 3He diffusion in concentrated phase is quasi-one-dimensional with unusually large diffusion coefficient 10-5 cm2/s, whereas magnetization changes and spin-lattice relaxation time coincide with those for bulk solid 3He.
NQR Investigations of High-Tc-Superconducting Oxides
Authors: Riesemeier H. , Grabow Ch. , Lüders K. , Müller V. , Geiser V. , Guntherodt H.-J.
Published: March 2014

NQR measurements on 139La and 63,65Cu in powdered La–Ba–Cu–O and Ba–Y–Cu–O compounds are reported. The temperature dependence and the distribution of the quadrupole frequency νQ is investigated for both the normal and superconducting state. In Ba2YCu3O7 a steep decrease of νQ at Tc is observed followed by an increase with decreasing temperature.
Measurements on Polarized Liquid 3He at Very Low Temperatures
Authors: Kranenburg C. C. , Wiegers S. A. J. , Vermeulen G. A. , Jochemsen R. , Frossati G.
Published: March 2014

Moderately polarized liquid 3He at temperatures as low as 30 mK has been obtained using rapid melting of polarized solid. Viscosity measurements using a vibrating wire and measurements of the relaxation time constant T1 at 300 MHz are presented. A sharp change in T1 as a function of time has been observed, from a short T1 at the beginning of the decompression to a rather long relaxation time afterwards. The effective temperature dependence of T1 is given by T1∼T-1, while a T-2 dependence is expected for intrinsic relaxation. Initial viscosity measurements indicate an in-crease in viscosity with increasing polarization, but this is subject to further confirmation.
Pumping of Dilute Polarized 3He–4He Solutions by a Magnetic Field Gradient
Authors: Guénault A. M. , Hayward D. J. , Nichols T. R. , Pickett G. R. , Spencer G. F.
Published: March 2014

An experiment is described which is aimed at demonstrating the pumping effect of a magnetic field on dilute (0.01-0.03%) solutions of 3He in 4He. At 4 mK and 10 T, conditions are reached such that the Fermi “gas” of 3He becomes spin-polarized and the polarizing magnetic field strength acts as the quantum mechanical potential for the system. In our experiment, a magnetic field gradient is applied, so that the 3He finds its lowest energy states in the high-field region and the low-field region is depleted of 3He. The pumping (and thus indirectly the polarization) is observed as a concentration change in the low-field part of the experiment as the 3He is removed. We making preliminary experiments to observe this effect by using a vibrating wire resonator and by capacitance methods. Once we can demonstrate that a gradient of 3He concentration can be set up then there are several interesting experiments which can be contemplated.
Exact Determination of the bbb Incoming State for Recombination in H ↓
Authors: Goey L. P. H. de , Stoof H. T. C. , Verhaar B. J. , Glöckle W.
Published: March 2014

We present the exact three-body wavefunction of the bbb incoming state, needed to determine the rate of recombination in H↓. Comparisons are made with the wave function of Kagan.
The Role of Final State Correlations in Recombination of Atomic Hydrogen
Authors: Stoof H. T. C. , Goey L. P. H. de , Verhaar B. J. , Glöckle W.
Published: March 2014

We calculate the rate-constant for recombination in the bulk of a spin-polarized atomic hydrogen gas. We use an exact initial state and include the most essential collision aspects of the final state, except for rearrangement.
New Measurements of the Two Superfluid Phase Transitions in 3He–4He Films
Authors: Wang X. W. , Gasparini F. M.
Published: March 2014

We report new observations at the superfluid phase transition of 3He–4He films by measurements of the normal mass. After the total coverage of 3He–4He reaches one active layer two superfluid transitions are observed as has been reported earlier, although some features of these transitions do not seem to reproduce identically. These data provide further information about the phase diagram of 3He–4He mixture films.
Low Frequency T
1 Measurements of 3He on Grafoil
Authors: Friedman L. J. , Bozler H. M.
Published: March 2014

Surface dominated thermal relaxation of 3He nuclei in confined geometries results in very short T1 values. Measurements of T1 have always shown a linear dependence on both the temperature and applied field. However, prior to this work the applied field has always been well over 10 gauss. Here we use a dc SQUID to extend T1 measurements down to applied fields below one gauss. We report on T1 measurements for 3He confined by a grafoil substrate. When the Larmor frequency is below 20 kHz we observe T1 values that gradually become less field dependent and eventually approach a constant. At present there are no models that fully explain the magnetic field dependence.
Rapid Nuclear Spin Depolarization of Small Particles Immersed in Liquid He
Authors: Goto Takayuki , Komori Fumio , Kobayashi Shun-ichi
Published: March 2014

Anomalously fast nuclear spin depolarization in low magnetic field is observed in tin small particles immersed in liquid 3He–4He mixture at 30mk. In order to specify its origin, the measurement in pure 4He is performed. The survey is extended to fluorocarbon particles.
Superfluid Transition of 4He Film Adsorbed on Packed Fine Powder
Authors: Minoguchi Tomoki , Nagaoka Yosuke
Published: March 2014

The superfluid transition of thin film of 4He adsorbed on packed fine powder is studied theoretically with emphasis on the role of vortices. In this system the film forms a three-dimensional, multiply-connected network. It is shown that the interaction between vortices is proportional to the distance between vortices like a `string' due to the quantum behavior of the flow, and that the vortices are `confined' at low temperatures. The stiffness of a string connecting two vortices is calculated by renormalization. It is found that the transition takes place with the appearance of free vortices at the transition temperature which depends on the particle diameter.
Temperature Dependence of S(Q, ω) for Liquid 4He at High Pressure
Authors: Svensson E. C. , Stirling W. G. , Talbot E. , Glyde H. R.
Published: March 2014

The results of a detailed neutron scattering study of the temperature dependence of S(Q, ω) for liquid 4He at 20 bars are presented. As was observed in an earlier study at saturated vapour pressure (SVP), it is found that there is a qualitative change in the character of S(Q, ω) on passing through Tλ and that one-phonon excitations are unique to the superfluid phase. The results are analysed in terms of the Woods-Svensson model, which does not give as good a description as at SVP, and one-phonon intensities, frequencies and intrinsic widths are extracted.
Experiments on the 19F Dipole-Dipole Reservoir in Polytetrafluoroethylene
Authors: Chapellier M. , Geng Q. , Olsen M. , Rasmussen F. B. , Schuhl A.
Published: March 2014

In polytetrafluoroethylene, we have cooled the dipolar reservoir of the fluorine nuclei. In a field of 2.5 Tesla the dipolar relaxation time is approximately 80 s at 3 K and 150 s at 1.8 K. The Zeeman reservoir relaxes in times 50 - 100 times longer. In the material used (a teflon powder produced by Aldrich-Chemie) the Zeeman relaxation time depends on contact to 3He at the surface, contrary to the dipolar relaxation time.
Structure of 3He–4He Thin Films
Authors: Laheurte J. P. , Noiray O. C. , Romagnan J. P. , Papoular M.
Published: March 2014

The existence of different structures in 3He-4He thin films, depending on temperature andthickness, has been assumed in view of many experimental results. We would like to show from a phenomenological description involving the various energetical contributions how the superfluid order in such films may favoured the homogeneous or cluster structures against the stratified one. Experimental observations could support this description. The structure evolution with temperature will also be discussed for different scenarios.
Crystallization Waves at the Solid-Liquid Interface of 4He
Authors: Agnolet G. , Osheroff D. D. , Sprenger W. O.
Published: March 2014

We report preliminary measurements of the dispersion and attenuation of melting and freezing waves at the solid-liquid interface of 4He for temperatures below 0.5 K. Both time of flight and resonance techniques were used to characterize the behavior of these waves. The measured dispersion agrees with the theoretically predicted form. The observed low temperature attenuation is found to be smaller than previously measured values. The kinetic growth coefficient K does not show a T-4 dependence as expected from phonons.
The He I-He II Interface in He4 and He3–He4 near the Superfluid Transition
Authors: Onuki Akira
Published: March 2014

HeI and HeII can be separated by an interface in gravity and/or heat flow. The interface structure can be examined by seeking a kink-like stationary solution to time dependent Ginzburg-Landau equations. However, a number of unsettled or unsolved problems can be raised on nonlinear effects in heat flow and on stability of the interface in heat flow and gravity.
An Ultrasonic Study of the Transition hcp-fcc 4He at 1.1 and 1.5 kbar
Authors: McGreer K. A. , Franck J. P.
Published: March 2014

Transverse ultrasonic sound velocity and attenuation at 3 MHz were studied in solid 4He at pressures of 1.1 and 1.5 kbar. The attenuation changed abruptly during the martensitic hcp-fcc transition. The high temperature phase (fcc 4He) had the higher attenuation. Between 8 K and the transition near 15 K the transverse sound velocity decreased up to 7%- an order of magnutude larger than the changes observed in 4He at lower pressures. These changes can be explained by the quasi-harmonic theory.
The Exchange Narrowing of T1 in Solid 3He
Authors: Matsumoto Kazuyuki , Izuyama Takeo
Published: March 2014

The exchange narrowing of the nuclear magnetic relaxation time T1 of solid 3He is investigated on the basis of the heat bath model. The exchange interactions are supposed to be described by the ring exchange model with two or three parameters. It is found that the three parameter model may explain the observed T1, data, but the two parameter model may not.
Electric Field Generated Forces in Liquid 4He and in 3He/4He Mixtures
Authors: Petrac D. , Israelsson U. K. , Jackson H. W.
Published: March 2014

A series of measurements are presented which show that it is possible to apply strong enough electric fields to liquid/vapor boundary interfaces in the quantum liquids to obtain electric forces comparable to gravity. The results are in good agreement with theoretical predictions [1,2]. We also present preliminary measurements showing the manipulation of the 3He-rich/3He-poor phase boundary in phase separated mixtures below 0.6 K. This opens up the possibility of developing a dilution refrigerator which can operate in space [3].
Deep Inelastic Neutron Scattering from Liquid and Solid Neon
Authors: Schmidt M. C. , Peek D. A. , Fujita I. , Simmons R. O.
Published: March 2014

To obtain single-particle momentum distributions, liquid and solid neon have been studied by means of pulsed inelastic neutron scattering at large values of momentum transfer Q (20-27 Å-1). The observed scattering is consistent with the impulse approximation, i.e. very well-defined peaks at the expected atomic recoil energy with a width proportional to Q. For saturated vapor pressure liquid at 27 K, analysis gives a kinetic energy in reasonable agreement with previous analysis by Sears of data for Q values below 10 Å-1. Our high Q measurements on neon solids at 12 K and higher temperatures, and on liquids at higher temperatures and pressure yield the first directly determined values for the kinetic energies under these conditions.
New Variational Approach to the Periodic Anderson Model
Authors: Yanagisawa Takashi
Published: March 2014

A new variational method is proposed for the ground state of the periodic Anderson model with infinitely large Coulomb repulsion. A wave function is the Gutzwiller type function which is an extension of the Varma and Yafet's wave function for the single impurity problem to the lattice case. The spin susceptibility of f-electrons calculated by this method is finite in the valence-fluctuation regime so that the ground state is stable against the ferromagnetic ordering.
Solution of the Anderson Model at N→∞ Using TFD of a Quantum Algebra
Authors: Hebron J. S. , Whitehead J. P. , Umezawa H.
Published: March 2014

Thermo field dynamics of a quantum algebra is applied to both the single-site and lattice cases of the N-fold degenerate, infinite U, Anderson model. The degenerate nature of the f-electron vacuum leads to a sector structure and vacuum diagrams. Propagators carry self-energies, and a “point-vertex” which arises due to the algebra of the Hubbard operators, and makes the propagators very different from the usual Feynman propagators. In the N→∞ limit, only the tadpole diagrams remain. The single-site case is solved self-consistently in this limit, showing a phase transition to a Kondo state at a temperature, Tκ, which agrees with the usual Kondo temperature. The lattice case, in the N→∞ limit, may be solved self-consistently using a “same-sector” approximation. This yields a phase transition at Tκ to a renormalized two band hybridization with a gap the size of Tκ at the Fermi surface, in agreement with the mean field results.
Origin of Heavy Electrons
Authors: Okada Kozo , Yamada Kosaku , Yosida Kei
Published: March 2014

The mass enhancement factor of f-electrons, \tildeγ, in the Anderson lattice is obtained by using the second order perturbation calculation with respect to the Coulomb interaction between f-electrons, U. The result shows that \tildeγ becomes large mainly because of the large unperturbed f-electron mass rather than because of large U.
Theory for the Heavy-Fermion State in Anderson Lattice
Authors: Koyama Tomio , Tachiki Masashi
Published: March 2014

To investigate the heavy-fermion state in Ce– and U–compound we study the low energy excited states of the Anderson lattice at low temperatures. The coupled Dyson equations are constructed in terms of the f-electron and spin-fluctuation Green functions in a one-loop approximation, based on the loop-expansion method. The calculated f-electron spectral functions clearly show the existence of quite heavy quasiparticle states at low temperatures and the crossover from the heavy particle states to an impurity-like kondo state at a relatively high temperature.
Spin-Orbit Coupling in Heavy Fermi Liquids
Authors: Yip Sungkit
Published: March 2014

We discuss the effects of spin-orbit couplings in Heavy Fermion systems that exhibit Fermi Liquid behavior. We argue that: (1) For given propagation direction with respect to the crystal, the velocity of longitudinal sound will depend on the direction of magnetic field even among the hitherto equivalent direction of the crystal; (2) For given wavevector \vecq, the transverse magnetic susceptibility χ(q, ω) exhibits satellite resonances and dependence on the observation direction of magnetization even among hitherto equivalent directions of crystal.
Measurement of these effects shall provide useful information on the strength of spin-orbit couplings in heavy fermion normal liquids.
Precision Measurements of the Magnetoresistance of CePb3, CePb2.97 and Ce.6La.4Pb3 at 50 mk
Authors: Fortune N. A. , Brooks J. S. , Crow J. E. , Lin C. L.
Published: March 2014

We have measured the magnetoresistance of polycrystalline CePb3 at 50 millikelvin in magnetic fields up to 20 tesla. At low magnetic fields, a positive magnetoresistance corresponding to the destruction of the antiferromagnetic ground state is observed, with a peak resistivity of 3 µΩ-cm. Above 5 tesla, we observe a pronounced negative magetoresistance, with the resistivity reduced to 0.6 µΩ-cm by a magnetic field of 20 tesla. Ce.6La.4Pb3 also exhibits a five fold reduction in resistivity in 20 tesla magnetic field. The magnetoresistance of Ce.6La.4Pb3 is well described by the single ion Kondo model for a double ground state, suggesting that the high field behavior of the heavy fermion system CePb3 may be similarly described. Measurements on the off-stochiometric CePb2.97 suggest that the high field resistivity is strongly sensitive to stochiometry. Within our experimental resolution, no magnetic field induced superconductivity was observed in these samples, contrary to some previous measurements of polycrystalline CePb3.
Gap Formation in a Valence Fluctuation System of CeNiSn
Authors: Takabatake Toshiro , Nakazawa Yasuhiro , Ishikawa Masayasu
Published: March 2014

We have found that CeNiSn is a typical valence fluctuating compound with a pseudo gap near the Fermi level. The valence fluctuating state in CeNiSn is gradually converted to Kondo regime by a partial replacement of Ni by Cu.
Magnetic and Transport Properties of Heavy Fermion Compound CePtSi
Authors: Sera Masafumi , Satoh Takeo , Kasuya Tadao , Sakurai Junji
Published: March 2014

The α-ThSi2 type intermetallic compound CePtSi is found to be a heavy fermion system with the electronic specific heat coefficient γ≃700mj/mole·deg2. The electrical resistivity, the magnetic susceptibility and the specific heat measurements suggest a nonmagnetic ground state.
Studies on the Valence State of Yb in YbTGa (T=Cu, Pd and Pt) Compounds through Magnetic Susceptibility Measurements
Authors: Malik S. K. , Adroja D. T. , Padalia B. D. , Vijayaraghavan R.
Published: March 2014

Compounds of the type YbTGa (T = Cu, Pd and Pt) have been synthesized. Magnetic susceptibility (χ) measurements reveal a maximum in χ-T at a temperature of about 200 K in YbCuGa, typical of the Yb containing mixed-valent systems. The Yb ions appear to be in a mixed valent state in YbPdGa also but in a divalent or nearly divalent state in YbPtGa.
Soliton Lattice Structure in the Spin Peierls System
Authors: Fujita M. , Machida K. , Korving K. H. , Brom H. B. , Jongh L. J. de
Published: March 2014

Spin-Peierls system TTF-AuBDT under magnetic fields is discussed experimentally and theoretically based on the mean-field Pytte Hamiltonian. Thermodynamic quantities such as magnetization, susceptibility and specific heat are derived, using the soliton lattice solution for the incommensurate state which takes into account infinite numbers of higher harmonics. We find that the theoretical curves are in good agreement with the experimental data.
Spin-Peierls Transition with Competing Interactions
Authors: Kuboki Kazuhiro , Fukuyama Hidetoshi
Published: March 2014

The one-dimensional spin-1/2 Heisenberg antiferromagnet which has next nearest as well as nearest neighbor exchange interaction and couples to the lattice distortion is investigated. The next nearest neighbor interaction is shown to result from the non-adiabaticity of the lattice distortion or the itineracy of electrons. The ground state of this system is investigated by the renormalization group treatment and the energy gain due to the lattice distortion is estimated by the self-consistent harmonic approximation.
Electric Response of Sliding CDW in Blue Bronzes
Authors: Nomura Kazushige , Fukuda Katsushi , Kohsaka Ryuta , Sambongi Takashi
Published: March 2014

The narrow band noise and pulse response measurements were done in the blue bronzes (K0.3MoO3, Rb0.3MoO3) to investigate the sliding motion of CDW. From noise spectra under dc bias current, the ratio of washboard frequency to the CDW carrying current density F1/JCDW was obtained as 11 and 14 kHz/A cm-2 in K0.3MoO3 and Rb0.3MoO3 and Rb0.3MoO3, respectively. These values well agree with the calculated ones due to the washboard model (F1/JCDW=1/enλ) and indicate that the CDW is sliding uniformly in a whole crystal. The transient oscillation of voltage response to a current pulse was also observed in the same samples and their frequencies were about twice as large as those of the narrow band noise. This suggests that the CDW begins to slide through limited cross sectional area at the initial stage of sliding CDW relaxes to the uniformly sliding state, which is stationary state under dc bias current.
NMR Experiments on Dilute 3He–4He Mixtures below 1 mK
Authors: Akimoto Hikota , Kawae Tatsuya , Oh Gong-Hun , Ishikawa Osamu , Hata Tohru , Kodama Takao , Shigi Toyoichiro
Published: March 2014

CW and pulsed NMR experiments on 3He–4He mixture of 6.4 % at 0 bar have been made down to 0.53 mK. The absorption signals obtained by a cw NMR method under the field gradient show the existence of several spin wave modes. These spin wave modes are excited at the same time by an rf pulse. The absorption signals are very different from those of the previous results.
DC Size Effect and Specular Surface Scattering in Cadmium
Authors: Maas Jacobus Van der , Huguenin Robert
Published: March 2014

Precision measurements of the electrical resistivity ρ(T) of a cadmium single crystal normal to the c-axis in the temperature range 1-9K are presented.The sample thickness d was reduced by chemical polishing from 1 to 0.04mm and the data were obtained for samples with mat and mirror-like surfaces. For all thicknesses etching a polished surface increases the residual resistivity ρ0 and decreases the temperature dependence of ρ. There is a minimum in ρ-ρ0 when d∼mean free path. A T2- variation of the surface resistivity is observed over a limited temperature range. These features are in qualitative agreement with the size effect theories including an angle dependent specularity parameter; the minimum is deeper and the T2- range more extended than predicted by the free electron model.
Dip and Hump Type Quantum Oscillations in Magnetoacoustic Attenuation in Semimetals
Authors: Mori Masatoshi , Koga Masao , Goto Nobuyuki
Published: March 2014

In the strong magnetic field, the deformation potentials of semimetals themselves make the dip and hump type quantum oscillations due to the change of the densities of states so as to satisfy the charge neutrality condition. When the magnetic field is perpendicular to the propagation direction of the sound, the giant oscillations are smeared by the tilt effect and the change of deformation potentials alone is dominant. Therefore the dip and hump type quantum oscillations appear directly in the line shape of the attenuation of the sound in this configuration. This result accords with the experimental ones for Bi1-x
Sb
x
.
Propagation of High-Frequency Phonons in Oxygen Doped Silicon
Authors: Werling Ulrich , Renk Karl F.
Published: March 2014

By use of a far infrared laser we excited the vibration of oxygen atoms in a silicon crystal at a frequency of 876 GHz and studied the propagation of phonons created by relaxation of the vibrational states. For phonon detection we used a tin bolometer on a crystal surface; phonons were generated within the crystal at different distances from the bolometer. We found that the phonons propagated diffusion-like; possible phonon scattering processes are discussed.
Dependence of the Phonoionization of A+-States in Si on Uniaxial Pressure
Authors: Groß Peter , Gienger Martin , Laßmann Kurt
Published: March 2014

By the new technique of phonon induced conductance we have investigated the dependence on pressure of the phonoionization response of shallow A+ - states in Si with superconducting Al-junctions as monochromatic phonon generators. In the case of B+ and Al+ we obtain a much more complicated behaviour than previously found for B+ with FIR-photoconductivity which may be connected with differences in coupling for short wavelength phonons. In the case of in+ on the other hand a shift to lower energies is observed for uniaxial pressure in [100]-direction whereas for pressure in [111]-direction only the signal intensity varies but not the position of the threshold.
Magnetoresistance of CdS Thin Film Bolometer
Authors: Guillon F. , Desjardins G.
Published: March 2014

We report on the magnetoresistance of CdS thin film bolometer at low temperatures.The usefulness of this detector for phonon emission study in semiconductors subjected to magnetic field, is discussed.
Localization and Interaction Effects in Metallic Polyacetylene
Authors: Thummes G. , Zimmer U. , Körner F. , Kötzler J.
Published: March 2014

The electrical conductivity σ(T) of heavily iodine-doped films of polyacetylene (CHIy)x, y≃0.25-0.3, has been investigated in the temperature range T = 20 mK -295 K and in magnetic fields up to 6T. We find that σ(T)=σ(0)+σ1(T), where σ(0)≃0-30 (Ωcm)-1 and σ(T)≃C√T below 150 K. The slopes C are close to the quasi-universal value of 6 (Ωcm)-1K1/2 reported for a variety of disordered metals. The observed magnetoresistance can be semi-quantitatively related to contributions from three-dimensional localization and electron-electron interaction effects. First results on (CHK0.12)x also reveal a √T dependence of σ1(T).
Nonlocal Effective Potentials and the Metal-Insulator Transition in Disordered Systems
Authors: Sorella Sandro
Published: March 2014

The metal insulator transition of a disordered electron system is analyzed using a new method based on Renormalization Group (R.G.) analysis.
It is found that, close to the transition (0°K), at the lowest order in perturbative expansion, the conductivity vanishes on the metallic side as in the non interacting case:

σ<(n-nc)µ,  with  µ=.5  or  1

depending on the absence or presence of time reversal symmetry in the electron system.
Oscillations in the Attenuation of Surface Acoustic Waves due to Proximity Coupling to a 2D Electron Gas
Authors: Schenstrom A. , Xu M-F. , Baum H. P. , Sarma Bimal K. , Levy M. , Qian Y. J.
Published: March 2014

Oscillations in the attenuation of Surface Acoustic Waves (SAW) was observed when a GaAs-AlGaAs heterojunction was placed in close proximity to the surface on which the SAW was propagating. These oscillations correspond to the oscillations in σxx, as a function of magnetic field, of the 2D electron gas on the interface between the GaAs and the AlGaAs.
Plasma Oscillations in Heterostructures and Superlattices
Authors: Sy H. K. , Song L. M.
Published: March 2014

We study an assembly of 2-D electron (hole) systems, separated spatially but coupled by Coulomb interaction. We investigate the plasma oscillations using coupled Boltzmann equations. An effective exchange potential calculated using the formalism of Kohn and Sham is included. The dispersion relation is obtained for both finite and infinite assembly. Surface modes are exhibited.
Intensity of the Far Infra-Red Absorption Band for a Disordered Polymer at Low Temperature
Authors: Yao Kai-Lun , Chu Xiao-Lin
Published: March 2014

Using equation of motion method of Green's function we calculate the far infra-red spectrum of a random polymer chain embedded as a self-avoiding walk on a dimond lattice. The Hamiltonian of the model includes stretching force, bending force and dihedral force. The results show that at low temperature the absorption peak is sensitive to the randomness of polymer chain, and the intensity of the absorption band has linear relation with the degree of crystallization.
Experimental Investigation on Spontaneous Magnetic Fluctuations in a Spin Glass System
Authors: Riemann Ph. , Vincent E. , Ocio M. , Hammann J.
Published: March 2014

Measurements of the free thermodynamic magnetization fluctuations have been performed in the thiospinel compound CdIn0.3Cr1.7S4, both above and below the glass temperature (Tg≃16.6 K), and in the frequency range 10-2-103Hz. From the fluctuation power spectrum, the out of phase susceptibility χ''(ω) is derived using the Fluctuation Dissipation Theorem. Systematic determinations of χ''(ω) around Tg enable us to analyse the critical behavior at the transition, on the basis of recent theories of dynamical scaling.
Magnetic Double Transitions in Quench-Condensed PdFe Films
Authors: Avirovic M. , Ziemann P.
Published: March 2014

To investigate the influence of disorder on the magnetic susceptibility of the giant moment system Pd1-xFex(0.005<x<0.06), films were quench-condensed onto liquid helium cooled substrates and stepwise annealed. The real and imaginary part of the magnetic susceptibility were measured in-situ. The experimental results give evidence for a crossover from ferromagnetic to cluster glass behavior, which depends strongly on the annealing temperature of the film, i.e. on the degree of disorder. Ferromagnetic to cluster glass double transitions were observed for 0.005<x<0.04 at different annealing temperatures.
Vortex Dynamics in Thin 4He Films
Authors: McQueeney D. F. , Agnolet G. , Wong G. K. S. , Reppy J. D.
Published: March 2014

Measurements of the Kosterlitz-Thouless transition in thin 4He films on a mylar substrate show a striking dependence on film thickness. We have studied films with transition temperatures (TKT) ranging from 67mK to 1.3K. Most of the transitions are too broad to fit the dynamic theory of Ambegaokar, Halperin, Nelson and Siggia. We observe four narrow regions of sharp transitions with TKT near .115, .550, 1.0 and 1.3 K.
Low-Temperature Ultrasonic Attenuation Measurements in Neutron-Irradiated Crystalline Quartz
Authors: Laermans C. , Vanelstraete A.
Published: March 2014

Ultrasonic attenuation measurements were carried out in neutron irradiated quartz for a dose that is higher and for temperatures which are lower than in previous experiments. The remarkable result is that although the sample is known to be mainly crystalline, a density of states of tunnelling centers is found which is similar to that in a compacted, but amorphous, form of vitreous silica.
Magnetic Ordering in Holmium Ethylsulfate below 215 mK
Authors: Xu Jingchun , Corruccini L. R.
Published: March 2014

We report ac and dc susceptibility measurements of single crystals of the axial dipolar paramagnet Ho(C2H5SO4)3·9H2O between 10 mK and 1 K. This material has hexagonal symmetry, with a non-Kramers doublet ground state possessing a very anisotropic g factor, to which the Ising model might be expected to apply: g||=15.41, g⊥=0. An antiferromagnetic transition was observed at ∼215 mK. This is in marked contrast to two related compounds with Ising model interactions, Dy(C2H5SO4)3·9H2O and Tb(C2H5SO4)·9H2O, both of which order ferromagnetically. A possible reason for the difference is the hyperfine interaction, which is large in holmium.
Dissipation in Gravitationally Driven Saturated Superfluid 4He Films
Authors: Israelsson Ulf E. , Jackson H. W. , Petrac D.
Published: March 2014

A new method utilizing a traditional two beaker geometry is used to study dissipation in moving 4He films. Data are obtained at temperatures between 1.5 K and Tλ, and the static film thickness is varied by a factor of two. Our results are analyzed using the intrinsic thermal fluctuation theory [1]. We find that the fluctuation frequency is essentially constant across the investigated temperature range, while the barrier velocity is proportional to ρs/ρT above 1.9 K. We also observe for the first time in a gravitational flow experiment the expected [2] decrease in the critical velocity as the lambda transition is approached. This decrease is found to depend on the geometry of the experiment.
The Thermal Expansion and Heat Capacity of Ni3Al
Authors: Collocott S. J. , Fawcett E. , White G. K.
Published: March 2014

The measured heat capacity Cp of a stoichiometric sample of Ni3Al from 0.5 to 15 K is qualitatively similar to earlier data: Cp≈8.9×10-3T+1944(T/470)3+0(T5) J/g.at K. The linear expansivity α can be represented by α≈-0.12T+0.0013T3 (×10-8 K-1) from 10 to 30 K but shows a marked decrease in α/T below 10 K and a jump of +10×10-8 K-1 above Tc≈41 K. The T and T3 terms lead to Grüneisen parameters γT≈-0.5 and γT3
≈2.5 respectively.
Production of Negative Spin Temperature in Pulsed Magnetic Field
Authors: Karaki Yoshitomo , Ishizuka Mamoru , Nakagawa Tadao , Amaya Kiichi , Haseda Taiichiro
Published: March 2014

Adiabatic demagnetization of Cs3CoCl5 is performed in a pulsed magnetic field. Cooling of the electronic spin system and the resulting spin ordering are observed in the course of the demagnetizing process. By increasing the sweep rate, a time constant corresponding to the antiferromagnetic arrangement, residual magnetization after the reversal of the magnetic field and the subsequent anomalous relaxation phenomena are observed.
Magnetic and Optical Properties of (BEDT-TTF)CuCl2 Complex
Authors: Tanaka Masashi , Kawamoto Atsushi , Tanaka Jiro , Sano Mitsuru , Enoki Toshiaki , Inokuchi Hiroo
Published: March 2014

The X-ray photoelectron spectra, the ESR spectra and the reflection spectra of (BEDT-TTF)CuCl2 complex were measured. The analysis of the X-ray photoelectron spectra shows that the Cu atoms in (BEDT-TTF)CuCl2 are in a mixed-valence state consisting of mono- and bi-valent cations and the concentration ratio of Cu(I) and Cu(II) is determined to be 2:1. The ESR signals show the presence of BEDT-TTF cation radical and Cu(II)Cl2. The temperature dependence of the magnetic susceptibility of these components were obtained from the ESR data. The polarized reflection spectra of the crystal show the CT2 band at 4000 cm-1 and the CT1 band in the vicinity of 11000 cm-1 . The results of the analysis of the ESR and reflection spectra support the presence of the mixed valence state.
Quantum Size Effect in Magnetic Field in Cu Small Particles
Authors: Kobayashi Shun-ichi , Katsumoto Shingo
Published: March 2014

In order to study the kinetic energy level correlation of conduction electrons in small metallic particles, we measured the magnetic field dependence of the Knight shift of 63Cu in copper small particles. We observed the suppression of the anomaly in spin paramagnetic susceptibility in the magnetic field so high that the Zeeman energy is larger than the average spacing of the energy levels. This suppression is explained as that the levels of electrons with opposite spins at the Fermi energy is lost in high fields.
EXAFS Study on Premartensitic Phase in A-15 Compounds
Authors: Sakashita Hirofumi , Kamon Kazuya , Terauchi Hikaru , Kamijo Nagao , Maeda Hironobu , Toyota Naoki , Fukase Tetsuo
Published: March 2014

Extended X-ray absorption fine structure measurements have been carried out near the Nb K-edge of Nb3Sn and the V K-edge of V3Si in order to investigate the local structure in the martensitic and the premartensitic phases. The first shell splits into three shells in the premartensitic phases. This implies that the local distortion with the low temperature martensitic structure takes place in the cubic phases of these A–15 compounds.
Heat Capacity of Nb–Ti Alloys from Upper Critical Field Measurement
Authors: De U. , Radhakrishnan T. S.
Published: March 2014

Upper critical field, Hc2 (T), vs. T data up to 12.5 Tesla, for β-quenched and then 400°C aged Nb–65at%Ti are reported as a function of aging. Inspite of a large peaking of the normal state resistivity, ρn, for about 2 hrs of aging, Hc2 (4.2K) is lower for this aging than for 525 hrs. after 80% cold work. Electronic specific heat coefficient, estimated from these measurements, shows large variations as a function of aging.
Critical Magnetic Fields of Superconducting NbN Films Prepared by Reactive Sputtering
Authors: Suzuki Mitsumasa , Baba Masahiro , Anayama Takeshi
Published: March 2014

NbN films with B1 structure have been prepared on sapphire and quartz substrates by rf sputtering, and investigated on their upper critical field Hc2 and its anisotropy. The superconducting transition temperature Tc of these films with thicknesses of 1500-6000 Å ranges from ∼12 to ∼16 K. Films deposited on quartz substrates have fine grains of B1 phase with the (111) plane parallel to the film surface and show higher values of Hc2. Films deposited on sapphire substrates contain an initial growth layer ∼1500 Å thick on which coarse columnar grains are formed. Both kinds of films show similar relationships between Hc2 and normal-state resistivity ρn, Hc2(4.2K) increases from ∼15 T with ρn in the range below ∼500 µΩ·cm and tends to saturate at above 500 µΩ·cm. The maximum Hc2 is obtained for a film with a ρn higher than 500 µΩ·cm and reaches ∼30 T. The Hc2 and its anisotropy are appreciably affected by the film microstructure and grain size.
Heavy-Axis Plasmon Mechanism for High Temperature Superconductivity
Authors: Ashkenazi J. , Kuper C. G. , Tyk R.
Published: March 2014

The new superconductors are very anisotropic; the electrons are “heavy” along one axis and “light” in the perpendicular plane. Plasma oscillations along the heavy axis have frequencies high compared with Debye, but low compared with Fermi energies. They interact strongly with the conduction electrons, because the copper 3d and especially the barium (or lanthanum) 4f orbitals are sensitive to charge fluctuations. Superconductivity follows ala BCS, but with much higher transition temperatures and no isotope effect. According to the present theory, the present of Ba and/or La is important for high-temperature superconductivity.
Tunneling Spectroscopy of High Tc Oxide Superconductors with a Scanning Tunneling Microscope
Authors: Ng K. W. , Pan S. , Lozanne A. L. de , Panson A. J. , Talvacchio J.
Published: March 2014

Tunneling experiments were performed on cleaved samples of high Tc oxide superconductors. The data can be fitted by introducing a current depairing term into the BCS density of states. This demonstrates the importance of depairing mechanisms in tunneling studies of these high Tc materials. Large Δ with 2Δ/kTc as large as 11 was obtained. The gap values are different for different junctions.
Electron Tunneling Study on Superconductivity of BaPb1-xBixO3
Authors: Akimitsu Jun , Ekino Toshikazu , Kobayashi Kazuaki
Published: March 2014

The electron tunneling measurements have been performed on the single crystal of BaPb1-xBixO3 with various x around x∼0.2. The observed density of states can well be described by the broadened BCS density of states proposed by Dynes et al, suggesting the gapless superconductor in BaPb1-xBixO3.
AlGaInP Visible Semiconductor Lasers
Authors: Ikeda Masao , Nakano Kazushi , Toda Atsushi , Mori Yoshifumi , Kojima Chiaki
Published: March 2014

The device characteristics of 680nm-band gain-guiding AlGaInP ion-implanted stripe double-heterostructure lasers with a GaInP active layer are presented. A narrow stripe laser with a stripe width of 8 µm showed a low threshold current of 68 mA, continuous-wave (cw) operation at a temperature as high as 68°C and a lifetime more than 3000 hours. The maximum light output power under cw operation was increased from 22 mW/facet to 250 mW/facet by broadening the stripe width to 60 µm. Two methods of shortening the emission wavelength are also discussed.
Lens and Optics for Optical Disk System
Authors: Tanaka Yasuhiro , Nagaoka Yoshitomi , Ueda Masaaki
Published: March 2014

Various types of pick-up lenses and optical systems for pick-ups are discussed. We evaluated optical performances of objective lenses. Aspherical lenses for CD player pick-ups have wider field angle compared to the conventional triplet objective lens. We also evaluated reliability of both plastic and glass molded lenses which are designed in the same way. Plastic lens caused spherical aberration due to temperature change. Optical pick-ups for CD players are remarkably simplified by means of aspherical lens or holographic element. On the other hand, pick-ups for write once or erasable optical disk system consist of many optical components. For these pick-ups, we developed a single bi-aspheric molded glass lens which has high NA (0.55) and remarkable light weight (85mg).
High Performance Optical Head using Optimized Holographic Optical Element
Authors: Kimura Yasuo , Sugama Seizin , Ono Yuzo
Published: March 2014

A high performance optical head, using a holographic optical element, which consists of only four optical elements, has been developed. The relief profile of the holographic optical element has been optimized to obtain high light power efficiency. As a result, the maximum light power efficiency has reached 14.8%. Holograms for detecting tracking error have been optimized to suppress tracking signal off-set. It has been experimentally shown that the tracking signal off-set does not appreciably arise.
High Speed Overwritable Magneto-Optic Recording
Authors: Nakao Takeshi , Ojima Masahiro , Miyamura Yoshinori , Okamine Shigenori , Sukeda Hirofumi , Ohta Norio , Takeuchi Yoshinori
Published: March 2014

To achieve high speed overwriting on magneto-optic disks, magnetic field modulation recording using a floating magnetic head has been developed. High reliability for the removable disks can be attributed to the large head-and-disk spacing(2∼4µm), and thick coating(5∼10µm) on the disk. Characteristics of high speed overwriting were investigated at recording frequencies over 10MHz. No residual pre-recorded signal was observed after overwriting.
NdDyFeCo for High Performance Magneto-Optical Disk
Authors: Sato M. , Tatsukawa S. , Tsukane N. , Mitani T. , Toba H.
Published: March 2014

Amorphous film of NdDyFeCo alloy has been investigated for high performance magneto-optical disk. Studies on magneto-optic effect and magnetic properties found that a square of hysteresis loop and a coercivity of (Nd13Dy87)30(Fe84Co16)70 were significantly improved, and large Kerr-rotation of 0.4 degree and Curie temperature of 150°C were obtained. Dynamic characteristics have revealed that magneto-optical disk of (Nd13Dy87)30(Fe84Co16)70 film on polycarbonate substrate(5.25''-diam. with track pitch of 1.6µm) had high C/N ratio of 58dB and 49 dB at 2MHz and 5MHz, respectively. This media also enabled to write data with a high sensitive power of 6.25 mW with a rotation speed of 1800 rpm at radius of 60 mm where should correspond to a rotation speed of 3600 rpm at radius of 30 mm. (Nd13Dy87)30(Fe84Co16)70 film promises the high data transfer rate recording of 10 Mbps for 5.25''-diam. is possible with high sensitivity under a recording power of 10 mW.
Photochemical Hole Burning: A High Density Storage Scheme
Authors: Haarer Dietrich
Published: March 2014

A short survey is given, summarizing the present efforts to understand the spectroscopic low temperature parameters, which characterize the storage scheme of photochemical hole burning (PHB). Using data of organic molecules which are monomolecularly dispersed in polymer matrices, one can show, that the PHB scheme is, in principle, feasible. At low temperatures one can expect a 103 to 104-fold increase in storage density as compared to conventional optical storage schemes. There are still many unresolved questions in the field of reading and writing schemes. To explain the ultimate limitations of the method the molecular parameters of the photoreactive systems have to be further studied; also novel scanning and detection schemes have to be explored.
Hole Burning, Stark-Effect and Holographic Image Storage
Authors: Wild Urs P. , Renn Alois , Locher René , Meixner Alfred J.
Published: March 2014

The technique of holographic spectral hole burning was used to characterize properties of potential recording materials for frequency and electric field selective data storage. Multiple storage of complex holograms was demonstrated.