bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantum Transport of Charged Interstitial in Metals
Authors: Weiss Ulrich , Wollensak Matthias
Published: March 2014

The dynamics of charged interstitials moving in a tight-binding lattice is studied at very low temperatures. The diffusion coefficient and the nonlinear mobility are shown to be strongly affected by the interaction with the conduction electrons. Recent results valid in order Δ2 where Δ is the effective tunnel matrix element are extended to all orders of Δ2. Exact results are obtained in analytical form in the case of weak damping K≪1 and for K=1/2 where K is the dimensionless defect-electron coupling strength introduced by Kondo.
Dynamics of the Phase Transition of Periodic Superconducting Networks
Authors: Jeanneret B. , Leemann Ch. , Martinoli P.
Published: March 2014

The critical behaviour of superconducting networks, as deduced from a study of the complex ac response of the system as a function of temperature, is found consistent with the vortex unbinding idea of the Kosterlitz-Thouless theory. The ac response of networks exposed to a perpendicular magnetic field shows a complex oscillatory dependence on the reduced flux per unit cell f=φ /φ0, with structures at integer and half-integer values of f.
Superconductivity in Coupled Pb/Ge and Pb/C Multilayers
Authors: Locquet J.-P. , Neerinck D. , Vanderstraeten H. , Sevenhans W. , Haesendonck C. Van , Bruynseraede Y. , Homma H. , Schuller Ivan K.
Published: March 2014

We report on measurements of the dimensional crossover effect in superconducting Pb/Ge and Pb/C multilayers. The critical field data indicate the presence of a proximity effect at the interface between the Pb and the Ge or C. Using the model of Tachiki and Takahashi, we calculate the finite density of states near the Fermi-level in the Ge and C layers.
Superconductivity in V/Si Multilayered Films
Authors: Hosoito Nobuyoshi , Mizutani Toshiyuki , Ohhashi Kentaro , Kanoda Kazushi , Mazaki Hiromasa , Shinjo Teruya
Published: March 2014

Multilayered V/Si films with artificial superstructure were prepared as a candidate of Josephson-coupled superconductors by alternate deposition in ultrahigh vacuum. Superconducting transition temperatures of V/Si multilayered films are compared with V/Ag cases studied previously. Annealing effects on the structure and superconductivity of V/Si films are reported.
Investigation of Superconducting BCC/FCC V/Pt, Nb/Pt Superlattices
Authors: Karkut M. G. , Triscone J.-M. , Fischer Ø.
Published: March 2014

We have magnetron sputtered multilayers of the bcc/fcc combinations Nb/Pt and V/Pt on (1120) Al2O3. Low and high angle x-ray diffractograms indicate good layering and coherence in the growth direction of about 400Å for V/Pt and 200Å for Nb/Pt. The residual resistivity of the V/Pt samples is anomalously high (58 to 94 µΩ cm) while Tc is strongly suppressed (0.8≤T
c≤3.0K for 80Å ≤Λ≤ 260Å) below what one would expect from a proximity effect calculation. Hc2(T) for both series has a 3-D like behavior at short A and a 2-D like behavior for longer Λ.
Upper Critical Fields of NbTi Based Multilayered Materials
Authors: Obi Y. , Ikebe M. , Muto Y. , Fujimori H.
Published: March 2014

NbTi/Ti and NbTi/Nb multilayered films with various layer wavelengths λ were prepared by a dual sputtering technique. Tc, Hc2// and Hc2⊥ were measured by a four-probe resistive method. Hc2// of NbTi/Nb showed remarkable enhancement compared with mother NbTi monolayer films, while almost nonenhancement was discernible in NbTi/Nb multilayer. A dimensional crossover effect observed in NbTi/Nb is caused by the difference of the electron diffusion constant D between NbTi and Nb.
Superconducting Properties of Nb Based Layered Films
Authors: Ikebe M. , Obi Y. , Kamiguchi Y. , Fukumoto Y. , Nakajima H. , Muto Y. , Fujimori H.
Published: March 2014

Nb/Al2O3, Nb/Ag and Nb/Ta multilayered films were prepared by an rf dual sputtering technique. Tc and Hc2// and Hc2⊥ were examined by a four probe resistive method. The λ (modulation wavelength) dependences of Tc and Hc2///Hc2⊥ of Nb/Ag and Nb/Ta are understood on the basis of the proximity effect and are in qualitative accord with the theory of Takahashi and Tachiki. The interlayer decoupling was so complete in Nb/Al2O3 that no dimensional crossover effect Hc2// was observable in the λ range studied(λ\gtrsim60A).
Calculation of Transition Temperatures of Superconductor-Metal Sandwiches
Authors: Auvil P. R. , Ketterson J. B.
Published: March 2014

The transition temperatures of superconductor-metal sandwiches and superlattices have been calculated. We employ the eigenfunction expansion of the de Gennes kernal near the critical temperature as implemented by Takahashi and Tachiki. We have modified these equations and results by consistently including a cut-off at the Debye frequency in the associated matrix elements of this theory and by approximately diagonalizing the eigenvalue equations. Our results show a much steeper decrease of the transition temperature with layer thickness than the Werthamer one mode approximation.
Critical Temperature of Superconductor/Ferromagnet Superlattices
Authors: Dobrosavljević-Grujić L. , Radović Z.
Published: March 2014

We calculate the suppression of the superconducting critical temperature Tc due to the proximity of the ferromagnetic layers which cause strong pair-breaking. The dependence of Tc on the thickness and intrinsic characteristics of single layers is evaluated.
Boundary Conditions and Spatial Variations Associated with the Dynamic Modes of Josephson Tunnel Junctions
Authors: Meepagala S. , Chang Jhy-Jiun , Chen J. T.
Published: March 2014

The Dynamic modes of Josephson Tunnel junctions have been investigated by the scanning laser technique and numerical simulations. The results clearly demonstrate the existence of the vortex mode and electromagnetic cavity mode which have distinctly different dc current distributions. The appropriate boundary condition used for calculations to describe our junctions was found to have the bias current fed from the edges.
Superconductive Behavior of a Proximity-Coupled Fibrous Superconductor
Authors: Ishida Takekazu
Published: March 2014

We have investigated the magnetic response of fine multifilamentary Nb-Ti wires in terms of complex susceptibility χ' -
i
χ'' The superconductive behavior is characterized by two distinctive transitions in χ' The onset temperature of the lower transition strongly depends on the direction of the magnetic field with respect to fiber axes. This can be interpreted by the difference in the percolating thresholds. It has also been found that the nature of the transition in the perpendicular field is strongly dependent on frequency.
Muon Diffusion in Superconductors
Authors: Hedegård Per
Published: March 2014

The diffusion constant of muons in superconductors is shown to have a T
-5 behavior for temperatures lower than the superconducting transition temperature. Unlike the normal state, where the temperature dependence is determined by the coupling to the electronic degrees of freedom, this law is derived from coupling to the lattice degrees of freedom. The coherence damping is furthermore so small that the muon can perform many coherent tunneling hops before coherency is lost.
Soliton Diffusion at Low Temperatures
Authors: Ogata Masao , Wada Yasushi
Published: March 2014

Friction of a soliton is studied in the one-dimensional φ4 system. It is generated by momentum transfer between the soliton and phonons. Quantum statistics is used for the phonon distribution It has the temperature dependence of the activation type, since the number of thermally excited phonons reduces drastically. The lowest frequency of the extended phonon modes plays the role of the activation energy. The result is compared with the soliton in trans-polyacetylene.
Superconductivity in AIVBVI Semiconductor Compounds with Quasilocal Impurity States
Authors: Shelankov A. L. , Shamshur D. V. , Parfeniev R. V. , Drabkin I. A.
Published: March 2014

Superconductivity in an impurity band is studied with reference to tin telluride doped with indium. A theoretical model is put forward, which relates a high critical temperature of the low carrier density IV-VI compounds doped with group-III elements to the interaction between the lattice and quasilocal impurity states.
Surface Flux Pinning Effects on the Critical State of a Type II Superconducting Slab
Authors: Saif A. G. , Refai T. F. , Shehata L. N.
Published: March 2014

Using the critical state model, the structure of surface flux pinning in a type II superconducting slab of finite thickness is studied. The surface barrier disappears when the external field approaches a superheating field. The flux lines (FLs) metastable state appears when the external field reaches a supercooling field. The critical superheating and the supercooling fields depend on the applied field orientation and the self field generated by a transport current flowing through the slab.
Explosive Dynamics of Thermomagnetic Instability in Superconductors
Authors: Maksimov I. L.
Published: March 2014

The explosive behavior of thermomagnetic disturbances is found to exist on the final stage of critical state instability development in type-II superconductors. It is shown, that nonlinear interaction between two thermomagnetic shock waves is responsible for the explosive critical state dynamics in high-κ superconductors. The velocity is determined of propagation of the normal-superconductive zones boundary, the explosion stage duration time is evaluated. The estimations are made for the explosive instability experimental observation in macroscopic superconducting samples.
Flux Line Shear Studied in Sputtered NbN Films
Authors: Pruymboom A. , Hoondert W. H. B. , Zandbergen H. W. , Kes P. H.
Published: March 2014

It is shown that above B≈0.5Bc2, the critical current density of sputtered NBN films is limited by flux line shear.The channel width for shear is determined by the lattice spacing rather than by the grain size.
Possible Observation of Charging Energy Effects in Single Ultra-Small Josephson Tunnel Junctions
Authors: Iansiti M. , Johnson A. T. , Smith Walter F. , Lobb C. J. , Tinkham M.
Published: March 2014

We report measurements of the current-voltage characteristics of small single tunnel junctions at temperatures between 4.2K and 23mK. Sample parameters are such that their estimated single electron charging energy is comparable to or greater than their Josephson and thermal energies. As the normal resistance increases to the order of the quantum resistance the behavior of the devices studied becomes fundamentally different from that of conventional Josephson junctions. We suggest an interpretation of our low temperature observations which takes into account the competition between the charging, Josephson, and thermal energies of the system, within the framework of a Bloch function description.
Effect of Trapped Flux and Temperature Variations on 1/f Noise in RF SQUIDs
Authors: Lockhart J. M. , Kingston J. J.
Published: March 2014

We have studied the correlation of the 1/f noise level in an RF SQUID, at frequencies from 1 Hz down to below.001 Hz, with the amount of trapped magnetic flux in the SQUID structure and the magnitude of its temperature fluctuations. Trapped flux levels corresponding to cooldown fields from 0.6 G to less than 10-7 G were obtained through the use of appropriate magnetic shields coupled with a special feedback-controlled cooldown technique designed to minimize the trapping of thermoelectrically generated flux. Temperature fluctuations were measured with high resolution thermometry and were controlled in some cases to 10 µK. Results show decreased low frequency 1/f noise under conditions of low trapped flux and highly-stabilized SQUID temperature.
Imaging the Behavior of Single Flux Quanta Trapped in Josephson Tunnel Junctions
Authors: Mannhart Jochen , Huebener Rudolf P.
Published: March 2014

Using Low Temperature Scanning Electron Microscopy we have two-dimensionally imaged single transverse flux quanta trapped in Josephson tunnel junctions. The force of individual pinning sites has been measured by observing the escape of the flux quanta from the pinning center under the influence of an applied Lorentz force. The spatial distribution of the maximum DC-Josephson current for the case of trapped flux quanta has also been calculated using a novel iteration technique and was found in excellent agreement with our experimental observations.
On the Noise Rise in an X-Band Microbridge Parametric Amplifier
Authors: Andresen J. E. , Levinsen M. T.
Published: March 2014

The anomalous noise-rise in Josephson parametric amplifiers has been an intriquing as well as annoying problem for many years. We have investigated unbiased single microbridge amplifiers, where the slit with the bridge is used as a slotline resonantly coupled to the wavequide. High gain with noise rise was seen. An analog computer study on a model including an input - output circuit was performed. The results are in nice agreement with the experiments. The amplification is heralded by a seemingly chaotic noise rise but a closer analysis seems to favour the idea of loss of phaselock
Subharmonic Generation in an LC Resonant Josephson Tunnel Junction
Authors: Olsson H. K. , Claeson T.
Published: March 2014

We have measured up to 4 subharmonics at 10 GHz in an LC resonant Josephson tunnel junction by using the internal Josephson oscillator as a frequency tuned pump. The oscillator linewidth (6.5 MHz), output power (5 pW), and resonance Q-value (100) for the fundamental oscillation , n=1, agreed with the RSJ model for low critical currents. However for large critical currents and n=1 to 5, narrower linewidths (6.5 to 0.5 MHz), higher output power (5 to 60pW) and different Q's (40 to 530) were observed. These are interesting properties for oscillators where high power,narrow linewidths, and small Q's are required.
Transient Response of Superconducting Tin Microbridges to Supercritical Current Pulses
Authors: Hansen J. Bindslev , Davidson A. , Brady M. , Pedersen N. F.
Published: March 2014

We report on measurements of the transient response of long tin microbridges to current pulses exceeding the critical current. The voltage response was investigated by the use of superconducting sampling and pulse-generation circuits. Analysis of the delay time until the normal state voltage develops gives an estimate of 150 picoseconds for the inelastic electron-phonon scattering time in tin. We have also investigated fast voltage pulses which apparently are induced by the current-driven motion of flux-tubes across the bridges.
Temperature Dependence of Current-Voltage Characteristics of Nb–Cu–Nb Bridges
Authors: Nakano Hiroshi , Aomine Takafumi
Published: March 2014

We have measured the current-voltage (I–V) characteristics of planar SNS bridges obtained by a simple fabrication method and compared them with the models. When the temperature T decreases far from the critical temperature T
c or the current region extends to the value much larger than the critical current I
c, the I–V characteristics are not in consistent with the Resistively Shunted Junction model using the electric resistance near I
c. When T is not far from T
c and the current region includes I≫I
c, the I–V characteristics of the bridges with appropriate length agree with the calculation using the time dependent Ginzburg-Landau (TDGL) theory. At T≪T
c, the I–V characteristics cannot be explained by the TDGL theory.
Preparation of Large Area NbN/AlN/NbN Josephson Junctions
Authors: Song S. N. , Jin B. Y. , Yang H. Q. , Ketterson J. B. , Schuller Ivan K.
Published: March 2014

AℓN has been used as a barrier material in large josephson junctions. The chemical and structural compatibility of AℓN with NbN make it possible to fabricate NbN/AℓN/NbN junctions by sequential reactive sputtering in a common Ar and N2 atmosphere. In a junction with an area of about 1.0×1.0 mm2, having a transition temperature of 14.5K. the measured I–V and first derivative curves yield a sum gap value of about 3.0 meV.
Bloch Oscillations and Phase Transitions of Josephson Junctions with Dissipation due to Quasiparticle Tunneling
Authors: Schön Gerd , Guinea Francisco
Published: March 2014

We investigate the macroscopic quantum mechanical properties, response and phase diagram of a Josephson junction where the dissipation and noise are due to quasiparticle tunneling.
Oscillations of Josephson Supercurrent in Pb/Al/AlOx/Pb Junctions
Authors: Yang H. C. , Liang L. K. , Horng H. E.
Published: March 2014

Osccillations of the Josephson supercurrent have been observed in Pb/Al/AlOx/Pb junctions. The oscillations only occur in the temperature dependence of the supercurrent in a constant magnetic field. Causes for these oscillations are discussed in terms of the change of the London penetration depth and the Josephson penetration depth with temperature.
Modulation Depth of Nanobridge dc-SQUIDs Made from High-κ Superconductors
Authors: Rogalla H. , Mück M.
Published: March 2014

Dc-SQUIDs from high-κ-superconductors like Nb3Ge show good modulation in their IV-characteristics up to about 20K. The modulation depth is a function of temperature and the SQUID area and deviates significantly from predictions of the RSJ-model. Computer simulations for the behavior of these dc-SQUIds are in good agreement with the observations.
Spin Paramagnetic Effect on Dirty Thin-Film Superconductors
Authors: Suzuki Takao , Seguchi Yasuhiro , Tsuboi Takefumi
Published: March 2014

We have observed a high entropy superconducting state in Al thin films from tunneling experiment. The deconvolution of tunnel spectra revealed that the density of states at the Fermi level was
higher in the superconducting state than in the normal state. This comes from the spin paramagnetic splittings of the quasiparticle excitation spectra and a small spin orbit scattering in Al metal. In contrast to this, we have found that the spin orbit scattering strongly suppressed the high entropy state and have observed only the first order transition for the thinnest films of V metal except for the reentrant transition, which was observed in Al thin films.
A Gyromagnetic Electron Gyroscope
Authors: Cerdonio M. , Bonaldi M. , Falferi P. , Prodi G. A. , Vitale S.
Published: March 2014

We recently proposed a detector of absolute angular velocity based on the difference between the gyromagnetic factor of the Cooper pairs in a superconductor, 2mc/e, and that of electron spins in a magnetic material, 2mc/ge with g∼2. The detector, which does not contain moving parts, is based on the measurement of the Barnett magnetization of a ferromagnetic rod enclosed in a corotating superconducting shield. Here we present an extensive experimental demonstration of the principle of operation.
The Gas Thermometer as Interpolating Instrument below 24.6 K
Authors: Steur Peter P. M.
Published: March 2014

In the light of its future incorporation in the next International Temperature Scale detailed calculations have been made on the behaviour of an Interpolating Gas Thermometer (IGT) below 24.6 K. These calculations show that such an instrument can be accurate to within 0.5 mK. Extending the interpolation range by using the IGT as an (semi-)absolute gas thermometer one could reach 0.8 K with the same accuracy, to join the (future) He-3 Melting Curve Scale.
Determination of h/m* Using a Rotating Niobium Ring
Authors: Tate J. , Cabrera B.
Published: March 2014

A precise measurement of the ratio of Planck's constant to the mass of a Cooper pair of electrons, h/m
*, may be made using a rotating, superconducting ring. When the ring is stationary, the flux threading it is an integer multiple of the flux quantum, h
c/e
* (e
*=2e). When the ring rotates there is an additional contribution to the flux, proportional to the rotation rate, from the London moment field, 2m
*
cω/e
*. The rotation velocities at which the flux is zero are therefore a set of evenly spaced points, separated by Δω. If the cross sectional area of the ring is S, then h/m
*=2SΔω. We have obtained new data in this experiment and are in the process of measuring the expansion coefficient of our quartz rotor in order to correct the room temperature area measurement.
A Compact High-Circulation 3 mK Dilution Refrigerator with HCP Vertical Heat Exchangers
Authors: Guénault A. M. , Hayward D. J. , Miller I. E. , Nichols T. R. , Pickett G. R.
Published: March 2014

We describe a very compact dilution refrigerator with base temperature below 3 mK and the potential for a large circulation rate. The heat exchangers, of sintered silver “Grenoble” type, are straight and very simple to make. The exchangers are stacked vertically in a hexagonal array with alternate “up” and “down” flow paths for economy of space. Such a configuration alone presents difficulties in initial filling and also gives rise to instabilities during running. A simple “short-circuit” can be used to cure all these problems. The resultant machine is easily filled and runs without instabilities. The design allows high power dilution refrigerators to be used in dewars of much smaller diameter than is customary now, with heat exchangers which can be readily made in any laboratory.
Versatile Low Temperature and High Magnetic Field Thermometers: The Low Temperature Magneto Resistance of Thin Film Cermets
Authors: Gershenfeld N. A. , Cleve J. Van , Graf M. J. , Fortune N. A. , Brooks J. S.
Published: March 2014

The magnetoresistance of a Pt-Al-O composite has been studied in fields up to 20 tesla and at temperatures down to 50 mK. The fill fraction of Pt is 0.44. The magnetoresistance is found to saturate above 2 Tesla at a value only 5% less than that of the zero field resistance.
Nuclear Spin-Lattice Relaxation in Metals at Low Temperatures
Authors: Turrell B. G. , Eska G. , Masuhara N. , Schuberth E.
Published: March 2014

In NMR experiments on metals at low temperatures, the analysis to obtain the nuclear spin-lattice relaxation time τ1 can be complicated because the lattice thermal capacity becomes small and other thermal resistances to the heat flow to the thermal bath can become significant. A theoretical model is developed which gives consistent results for κ=τ1T when applied to experimental data obtained for Pt powder over a wide range of experimental conditions.
Two Different Vortex States In Rotating 3He–A Observed by Use of Negative Ions
Authors: Nummila K. K. , Simola J. T. , Skrbek L. , Korhonen J. S.
Published: March 2014

First experiments suggesting the presence of singular vortices in rotating 3He–A are reported. We have studied the interaction between negative ions and vortices by utilizing the focusing of ions by vortices. Our results verify the existence of continuous vortices seen earlier by NMR, but evidence for a new vortex state with high ion mobility along the core was also found. The nucleation of the new vortex state depends on the external magnetic field and the rotation history of the sample.
Possible States for a Three-Dimensional Electron Gas in a Strong Magnetic Field
Authors: Halperin Bertrand I.
Published: March 2014

If a three-dimensional semimetal or doped semiconductor is placed in a sufficiently strong magnetic field, then a change in its transport properties will occur. If the electron-impurity interaction is dominant, then the magnetic field will produce localization of the electron wavefunctions, sometimes described as magnetic freezeout. If the electron-electron interaction is more important, then some type of collective transition may occur. Spin-density waves, charge-density waves, valley-density waves, excitonic insulators, and Wigner crystallization have been proposed to occur under various circumstances. As a generalization to three-dimensions of the integral quantized
Hall effect, we show that for electrons in periodic or quasiperiodic potential, when the Fermi level lies in an energy gap, the zero temperature conductivity tensor is given by σ
i
j
=(e
2/2πh)∑
k
ε
i
j
k

G

k
, where \vecG is a reciprocal-lattice-vector of the potential. We discuss the effect of impurities and dislocations on this result.
Localization in Two-Dimensional Systems in Quantum Hall Regime
Authors: Ando Tsuneya
Published: March 2014

A recent development in understanding the problem of electron localization in two-dimensional systems in strong magnetic fields is reviewed mainly from a theoretical point of view with emphasis on relation to the quantum Hall effect. The results of numerical study are described in detail, but other theoretical approaches like perturbation theory are discussed more briefly.
Critical Behavior and Magnetic Fluctuations in Spin Glasses
Authors: Bouchiat H. , Courtenay N. de , Monod P. , Ocio M. , Refregier P.
Published: March 2014

After many years of controversies it appears now that the that glassy-like behavior of spin glasses at low temperature is not in contradiction with the existence of a well defined phase transition. We discuss here in a non exhaustive way some static and dynamic experimental results which among others, contribute to shed light on this question.
Rotating Superconductors and the Cooper Pair Mass
Authors: Cabrera Blas
Published: March 2014

A review is presented of the theoretical and experimental work on rotating superconductors. By measuring the determination London field, BL=-(2m*c/e*)ω, with respect to the flux quantum, hc/e*, a precise of h/me is possible. Using this method, several experiments have obtained ever more with the most recent Stanford data at an accuracy of 20 ppm. There are no relativistic corrections to e* which is exactly 2e, but m*=2me only in the non-relativistic limit. Various relativistic corrections to m* lead to an observable mass m' which is smaller than 2me by about 10 ppm. Currently there is not satisfactory agreement between theory and experiment.
Organic Superconductors of BEDT-TTF Family
Authors: Schegolev I. F.
Published: March 2014

Some new results on the organic superconductors of BEDT-TTF family recently obtained in the U.S.S.R. are reviewed.
Arrays of Josephson Junctions: Model Systems for Two-Dimensional Physics
Authors: Martinoli P. , Lerch Ph. , Leemann Ch. , Beck H.
Published: March 2014

Planar arrays of Josephson junctions provide excellent model systems to study a variety of phase transitions in two dimensions. Experiments are reported in which the critical behaviour of periodic arrays is studied by measuring the dynamic response of the system to a small oscillating field. Tuning of frustration occurs by adjusting the magnetic flux threading a unit cell of the array, while by varying the driving frequency it is possible to probe the critical behaviour of the system at different length scales. The dynamic response near the phase transition of an un frustrated array is well described by a model incorporating the vortex unbinding mechanism predicted by the Kosterlitz-Thouless theory. Some aspects of the dynamic response of frustrated arrays are also discussed.
High-Temperature Superconductivity; Past, Present and Future
Authors: Tanaka Shoji
Published: March 2014

The history of the research on high-Tc oxide superconductors is reviewed. Fundamental physical properties of high-Tc oxides and its implication are described. Based on the experimental data presented so far, the potential future of these materials is briefly discussed.
High Field Behavior of Liquid and Solid 3He: A New Solid Phase?
Authors: Bouchaud Jean-Philippe , Lhuillier Claire
Published: March 2014

An anomaly of the solid to liquid coexistence curve for a total nuclear polarization of rougly 18% has recently been observed [1,2]. It has quite convincingly been interpreted as the signature of a possible new phase [1]. The exact nature of this phase is still to be characterized in details. We want here to emphasize that the presence of a new localized phase (vacancy solid phase) with an inhomogeneous polarization would be consistent with the actual knowledge of both “normal” liquid and solid phase and explain most of the observed experimental facts.
Thermal Detectors for High Resolution Spectroscopy
Authors: McCammon D. , Juda M. , Zhang J. , Holt S. S. , Kelley R. L. , Moseley S. H. , Szymkowiak A. E.
Published: March 2014

Thermal calorimeters operating in the millikelvin temperature range are capable of detecting single particle or photon interactions with deposited energy thresholds as low as a few electron volts. Small monolithic devices can be made using integrated circuit fabrication techniques and should have resolutions near 1 eV. Relatively crude test devices have already achieved resolutions for soft X-rays that are several times better than the best solid state detectors. It also may be possible to construct kilogram-scale detectors with thresholds less than 1000 eV. High resolution calorimeters have obvious applications in many types of spectroscopy, while the large-volume detectors would be useful for neutrino measurements and other rare interactions and decays. The truly unique characteristic of these large calorimeters as particle detectors is their sensitivity to non-ionizing interactions, and it has been proposed to use them to search for certain dark matter candidates and other exotic particles.
Observation of Negative Group Velocity Rotons in Liquid Helium
Authors: Wyborn G. M. , Wyatt A. F. G.
Published: March 2014

A novel experiment has been performed which gives direct evidence for the existence of long lived negative group velocity (R-) rotons in superfluid liquid helium at T = 0.1 K. Such excitations produced by the condensation of an atomic helium beam are found to propagate ballistically in the liquid, reflect specularly from a crystal surface and are able to evaporate atoms in a quantum evaporation process. The component of momentum parallel to the surface is conserved which shows that the momentum of the R- rotons is oppositely directed to the group velocity.
The Possible Current Path in Y-Ba-Cu-O Superconductors
Authors: Cui Guang-Ji , Meng Xiao-Fan , Ren Xue-Min , Dai Yuan-Dong
Published: March 2014

Weak-link neck form Y-Ba-Cu-O bulk superconductors were tested as a probe of the possible current paths inside the samples. The typical quasipartical style I-V curves were observed. The flux trap phenomena were also observed. These indicate that the current path might be through grain boundaries and a very complicated percolating network.
Radiant Er-Related Luminescence of High Tc Superconducting Er–Ba–Cu–O System
Authors: Fujiwara Yasufumi , Takahashi Tetsuro , Fukumoto Yoshito , Tonouchi Masayoshi , Kobayashi Takeshi
Published: March 2014

We describe the first observation of a highly radiant photoluminescence (PL) around 0.8 eV from Er–Ba–Cu oxides with a high superconducting transition temperature (Tc ). It consists of a series of sharp PL lines, tentatively assigned to intracenter transitions between the weakly crystal-field split spin-orbit levels, 4I13/2 – 4I15/2, of a trivalent Er ion incorporated in this oxide. The in-depth profile and the Ba content dependence of the Er-related luminescence have been systematically investigated and discussed. Similar luminescences have been also observed in three energy regions in Nd–Ba–Cu oxides.
Ab-Initio Calculation of the Electron-Phonon Interaction in Simple Metallic Systems
Authors: Zdetsis Aristides D.
Published: March 2014

Within the framework of the rigid muffin-tin approximation, it is shown that Hartree-Fock total energy cluster calculations can be combined with traditional band structure results to calculate truly ab-initio the mass enhancement parameter λ. The average phonon force constant m<ω2> is calculated ab-initio through the cluster results, whereas the electronic parameter η is calculated as usual from the band structure calculation.
This procedure, which can be enhanced with non-rigid muffin-tin corrections, emphasizes both the banding and the bonding characteristics of the electron-phonon interaction process. Besides the first few elemental metals for which an excellent agreement with experiment exists, the method has been recently applied to various bonding configurations of the high T

c
La-Cu-O superconductors. In this last case, the results are only preliminary.
A New Variational Description of Liquid 3He: The Quantum Glass
Authors: Bouchaud Jean-Philippe , Lhuillier Claire
Published: March 2014

We present a new variational wave function for liquid 3He which gives a good description of both elastic and magnetic properties of helium three at T=0. This description does not start from the usual Slater determinant of a degenerate ideal Fermi gas but emphasizes the role of strong-coupling pairing correlations in the normal liquid. Besides the good numerical agreement between our calculations of the binding energy, compressibility, magnetism, coherent and incoherent structure function and experiments, an altogether coherent picture of what could be liquid helium three at low temperatures emerges from our “heretic” approach. Due to the fermionic correlations, liquid 3He appears to possess a strong medium range order favouring quite convincingly the nearly solid pictures of Anderson and Brinkman, Castaing and Nozières, Vollhardt... On the other hand these strong fermionic correlations which coherently tie mesoscopic clusters of atoms (from 70 to a few hundreds when the pressure varies from solidification line to zero) support a new image for the low temperature excitations of the liquid. They are identified with the magnetic degrees of freedom of these mesoscopic clusters... Such a model does give back the low temperature thermodynamics of helium three without any call to Landau-Fermi liquid theory.
Quasihomogeneous Spin Waves with l=1 for Normal 3He in DC Magnetic Fields and Its Antiresonance
Authors: Czerwonko Jerzy
Published: March 2014

The dynamic spin susceptibility of the normal, degenerate and neutral Fermi liquid is found in the quasihomogeneous regime, with the accuracy ∼ (kR)2, at the collision integral taken in the ref. 1. The formula contains a spin wave pole with ℓ=1. This formula is used also to find the conditions when the ac magnetization term compensates the field H in the ac magnetic induction. The results are also valid for metals, if the vector k is directed along the dc magnetic field.
Surface Coupling to Collective and Single-Particle Spin Modes in Normal 3He
Authors: Bogacz S. A. , Ketterson J. B.
Published: March 2014

A simple technique is proposed for probing the single-particle and collective excitations in normal 3He via a standing magnetic surface wave of arbitrary ω and fixed k generated by a meander-line coil. The analytically calculated power absorption spectrum for 3He displays singularities associated with the l=0 spin mode and a Doppler-Shifted Spin Resonance of the single-particle excitations. Finally a possibility of exciting higer, l≥1, spin modes is discussed.
Sensitive Bolometric Detection of Atomic Hydrogen Fluxes
Authors: Berkhout J. J. , Höpfner O. H. , Wolters E. J. , Walraven J. T. M.
Published: March 2014

We developed a sensitive device to detect atomic hydrogen fluxes. The device is based on a measurement of the heating due to forced recombination of the atoms in the flux. We found that 60±10 % of the recombination heat is collected by the detector. The DC noise equivalent (1σ) flux Φ is 6×1010 at/s at a bandwidth of 0.4 Hz and a dynamic range of 1000 (Φmax=6×1013 at/s). The device may be used at ambient temperatures below 450 mK. We discuss possible improvements of the design.
Spin-Polarized Deuterium: Stabilization in Magnetic Traps
Authors: Koelman J. M. V. A. , Stoof H. T. C. , Verhaar B. J. , Walraven J. T. M.
Published: March 2014

We report on a calculation of the spin-exchange two-body rate constants associated with the population dynamics of the hyperfine levels of atomic deuterium as a function of magnetic field in the Boltzmann zero temperature limit. We find that a gas of low field seeking deuterium atoms trapped in a static magnetic field minimum decays rapidly into an ultra stable gas of doubly spin-polarized deuterium.
Phonon Scattering and Quasi-Diffusion in Liquid Helium
Authors: Ashworth S. P. , Wyatt A. F. G.
Published: March 2014

Phonons and rotons can be injected into liquid 4He by a thin film heater. It is shown that as the heater power is increased the phonon propagation goes from ballistic to quasi-diffusive. The evidence shows that the scattering region is near the heater and is probably initiated by injected slow rotons. A phonon probe technique is used to measure the lifetime of this region which is found to be ∼ 50 µs.
Heat Capacities of H2 and D2 in Some Restricted Geometries
Authors: Amaya Kiichi , Morita Naotake , Moriyasu Yoshitaka , Ishizuka Mamoru , Deguchi Hiroyuki , Takeda Kazuyoshi , Haseda Taiichiro , Yamanaka Shoji
Published: March 2014

Heat capacities of H2 and D2 adsorbed in restricted geometries of zeolites and montmorillonites are measured at temperatures below 20K. The results are strongly concentration dependent and give temperature dependence characteristic of resricted geometries. Einstein type temperature dependence in zeolite, broad maxima or anomalous peak in pillar intercalated montmorillonites are observed.
Viscous Waves in 4He Films
Authors: Fozooni P. , Spencer D. S. , Lea M. J.
Published: March 2014

A quartz crystal resonator was used to generate viscous shear waves, penetration depth ∼ 20 nm, in HeI and HeII films. The complex transverse acoustic impedance was measured and interpreted using transmission line theory. Normal films of thickness 1.5<d<60 nm were studied. Below T
λ, measurements were made on saturated films with 14<d<23 nm. An unexpected feature may be due to a standing wave resonance on vortices. The efficiency for the evaporation of atoms from the film surface by rotons was determined.
Superfluid 4He Films Adsorbed on Pt Packed Powder
Authors: Shirahama Kenya , Wada Nobuo , Takano Yasumasa , Ito Taro , Watanabe Takashi
Published: March 2014

The superfluid transition of 4He films adsorbed on Pt packed powders 500, 100, and 60 A in diameter has been studied using torsional oscillators. The behavior of the superfluid density near the transition differs considerably from earlier observations in films adsorbed on porous glass. For all the powder diameters, a narrow dissipation peak accompanies the transition unlike in the porous-glass case. The results are also In disagreement with the theories of the Kosterlitz-Thouless transition on a sphere.
The Registered Phase of Helium-3 Adsorbed on Grafoil
Authors: Cowan Brian , El-Nasr Laila Abou , Fardis Michael
Published: March 2014

Nuclear magnetic resonance has been used to study the registered phase of helium-3 adsorbed on grafoil. Spin-lattice and spin-spin relaxation times have been measured over a range of Larmor frequencies from 1 MHz to 10 MHz. There are two contributions to the relaxation: the internuclear dipolar interaction and the internal demagnetising field of the graphite. We are able to distinguish these effects. Dipole-dipole relaxation is well understood for two dimensional systems and the atomic motion has been analysed on this basis. At registry there is a reduction in the mobility of the adsorbate by approximately one order of magnitude. However, there still remains considerable temperature independent motion which we interpret as quantum exchange.
Search for Single-Particle Excitations in Super fluid 4He
Authors: Svensson E. C. , Tennant D. C.
Published: March 2014

From their neutron scattering measurements, Blagoveshchenskii et al. have inferred the existence of a new branch of free-particle excitations in superfluid 4He in the same wave vector region as the familiar phonon-roton excitations. We report the results of a detailed search for free-particle excitations in superfluid 4He using neutron scattering techniques. To a high level of sensitivity (≈ 0.01% of the roton intensity) we find no evidence for such excitations.
Experiments and a Model of 3He Magnetization near a Surface
Authors: Schuhl A. , Maegawa S. , Meisel M. W. , Chapellier M.
Published: March 2014

Magnetization of 3He confined by fluorocarbon microspheres has been studied between 13 and 150 mK and with an applied pressure from 0 to 32 bar. The relative weight of Curie-Weiss surface contribution is observed to increase smoothly with pressure. A thermodynamic analysis which predicts a growth of adsorbed solid as external pressure increases is in good agreement with our experimental data. The Curie-Weiss contribution and the surface ferromagnetism appear to result from adsorbed solid properties and do not seem to arise from a ferromagnetic 2D liquid as has been proposed.
Structures of D2 on MgO-Powder
Authors: Degenhardt D. , Lauter H. J. , Haensel R.
Published: March 2014

The structure of D2 monolayers adsorbed on MgO-powder with a highly studied with elastic neutron scattering. A commensurability of the adsorbate along the [100]-direction of the substrate has been detected for all coverages. Thus the D2 molecules are arranged in rows. At the highest measured monolayer coverage the spreading pressure accidentially adjusts the distance between the molecules along the rows so that a quasi hexagonal structure appears. This degeneracy is raised if the molecules relax along the rows with decreasing coverage and different types of ordering, i.e. commensurabilities along the rows, have been observed.
Neutron Diffraction Study of 1st-, 2nd- and 3rd-Layer D2 Adsorbed on ZYX-Graphite
Authors: Schildberg H. P. , Lauter H. J. , Freimuth H. , Wiechert H. , Haensel R.
Published: March 2014

The structure of Deuterium adsorbed on ZYX-graphite has been investigated for coverages ranging from 0.9 to 2.9 of the densest monolayer coverage. The first layer data are compatible with the already known triangular structure. The second layer promotion is explainable by assuming an oblique unitcell which it has in common with the first layer. Melting layer two will let layer one adopt its original triangular structure. The third layer condensed similarly by evoking the formation of an oblique unitcell for all three layers. The (101) reflection of this cell was detected.
The Mobilities of Ions Trapped below the Surface of Superfluid 4He
Authors: Mellor C. J. , Muirhead C. M. , Traverse J. , Vinen W. F.
Published: March 2014

Experimental measurements of the linewidths of plasma resonances in two-dimensional pools of both positive and negative ions trapped below the surface of superfluid 4He have been used to deduce the mobilities of these ions as functions of temperature (20 mK to 0.5 K) and depth below the surface. At the higher temperatures the mobilities can be described well by theories based on the scattering of bulk phonons, but at the lower temperatures the mobility becomes markedly depth-dependent and is therefore presumably limited to a significant extent by ripplon scattering. A theory of ripplon-limited mobility is described and compared with experiment. No anomaly in the mobility has been observed at the temperature at which crystallization of the ion pool is expected to occur.
The Power Dependence of the Quantum Evaporation of 4He by Phonons and Rotons
Authors: Brown M , Wyatt A. F. G.
Published: March 2014

Quantum evaporation of 4He atoms by phonons and rotons gives a method of studying the propagation of these high energy excitations in liquid 4He. If the heater pulse which creates the phonons and rotons is too energetic then there is mutual scattering within the beam. At low powers the excitations propagate ballistically and the created roton spectrum can be characterised by a temperature.
The Roughening Transition and the Surface Stiffness of Helium-3 Crystals
Authors: Rolley Etienne , Balibar Sébastien , Gallet François
Published: March 2014

New careful observation of helium 3 crystals, slowly growing in a transparent and deformable cell, show the existence of (110) facets on their surface up to T = 0.10 K. We independently measured the surface stiffness of these crystals. A preliminary result is 0.047 erg cm-2, a much larger value than expected from the temperature at which facets disappear.
Melting Pressure of Magnetically Ordered Solid 3He
Authors: Tang Y. H. , Adams E. D.
Published: March 2014

The melting pressure of 3He has proven to be a useful way to study magnetic ordering in the solid. The order of phase transitions are easily estsblished by observing the behavior or pressure vs. time in slow warming or cooling. In this way, the paramagnetic-to-high-field transition has been demonstrated to be second order of λ-type (no latent heat). The temperature dependence of the melting pressure P(T) gives information on the spin-wave spectrum. It is found that both the low- and high-field phases have P∝T4 , characteristic of an antiferromagnetically ordered state. Present measurements are being extended to lower temperatures and to fields of 1.1 T to determine the variation of spin-wave velocity with field.
Study of the Multiple Exchange Frequencies in bcc 3He by Thermodynamic Measurements
Authors: Bernier M. , Suaudeau E. , Roger M.
Published: March 2014

To study the multiple exchange hamiltonian of solid 3He we measured the contribution of the spin exchange to the pressure of bcc solid in various magnetic fields (0\leqslantH\leqslant7.5T). Due to the nature of the atomic exchange of a fermion system this contribution is a strong function of the spin polarization. The characteristic frequencies of the exchange hamiltonian are obtained by fitting the pressure measurements with the results of a statistical calculation using a high temperature series expansion of the the hamiltonian in a temperature range where both the magnetic effect is significant and the expansion converges (7mK<T<30mK). We discuss the results obtained for two molar volumes.
Specific Heat of Magnetically Ordered bcc 3He
Authors: Greywall Dennis S.
Published: March 2014

Precise specific-heat measurements have been made on low-density samples of bcc 3He for temperatures in the range 0.6 to 10 mK and for magnetic fields of 0, 6, and 10 kOe. When plotted as a function of T/Tc, the high-field data lie on a universal curve which exhibits a peak characteristic of a λ-type transition. It is also observed that Tc (10 kOe) ∝ V8.7, that vspin∝Tc(H), and that the field-induced increase in the paramagnetic phase specific heat is proportional to H2/T2 near Tc.
Theory of Ferromagnetic State of HCP Solid 3He for Pair, Triple and Quadruple Spin Exchange Interaction. II Green Function Theory
Authors: Iwasaki Tomio , Soda Toshio
Published: March 2014

There are two sublattices which we call A and B in hcp solid 3He. The equations of motion of the spins, Si
A+ and Si
B+ at the i-th site of each sublattice are calculated by their commutation relations with the multiple-exchange Hamiltonian including the most important two, three and four-particle exchange processes. Then we introduce the Green functions GAA and GBB. These Green functions and correlation functions are computed from the closed form of equation of motion. We derive a self consistent equation for the order parameter  using the spectral theorem, and compute  the Curie temperature TC, and other physical quantities using RPA.
High Temperature Series Expansions with a Multiple-Exchange Hamiltonian for the bcc and hcp Phases of Solid 3He
Authors: Roger M. , Suaudeau E. , Bernier M. E. R.
Published: March 2014

High temperature series expansions with a multiple-exchange Hamiltonian are performed to fourth order in arbitrary magnetic field for both phases of solid 3 He. The susceptibility series are analysed with Padé approximants and compared with recent experimental results. For the hcp phase we estimate the ferromagnetic ordering temperature from susceptibility series and discuss the influence of four-particle exchange in lowering the transition.
Effect of Conduction Electrons on Low-Temperature Properties of Intermetallic Compounds with Singlet Ground State
Authors: Ishii Hiroumi
Published: March 2014

In intermetallic compounds with singlet ground state the effect of conduction electrons on nuclear magnetism is studied. By eliminating the electronic freedom which carries the Van Vleck paramagnetism, the effective Hamiltonian is obtained, which describes a set of nuclear spins embedded in the electron sea with repulsive interaction. In terms of the susceptibility of the conduction electrons the effective Hamiltonian for nuclear spins is derived.