The Josephson coupling between a conventional and an unconventional superconductor is investigated as a function of the properties of the tunneling barrier. A simple model is adopted for the tunneling probability and it is shown that its variation dramatically affects the ${\mathit{I}}_{\mathit{c}}$${\mathit{R}}_{\mathit{n}}$ product of an s-d, as opposed to an s-s junction. Based on these conclusions, experiments are proposed to probe the symmetry of the order parameter in high-temperature superconductors.

Using two distinct methods, Huang, Gumbs, and Kolár̆ [Phys. Rev. B 46, 11 479 (1992)] find different results for the calculated transmission coefficient through a chain of N δ-function-shaped barriers. We explain that the origin of this difference is an erroneous formulation of the so-called optical method and we give its corrent version. All of the important results of the cited paper, which were obtained using the transfer-matrix method, remain correct.

We respond to the criticism of the preceding Comment.

We report the observation of strong amplitude variations with k in the 4f photoelectron spectra of a nearly trivalent heavy-fermion compound (${\mathrm{CePt}}_{2+\mathit{x}}$). The amplitude of the 4f feature, previously identified as the Kondo resonance, displays the full symmetry of the lattice, suggesting some band character already at T≊10${\mathit{T}}_{\mathit{K}}$. Kondo lattice-derived bands are expected to exist only at T≪${\mathit{T}}_{\mathit{K}}$, so that this would seem to favor conventional bands at high T. The single-impurity model by contrast demands purely localized behavior at these temperatures.

In this work an enhancement of the Curie temperature of the intergranular amorphous region in nanocrystalline alloys with respect to amorphous ribbons of the same composition is shown. The Curie temperature reaches a value of 125 °C. The experimental results are discussed in terms of both an inhomogeneous distribution of Nb atoms in the interphase and the magnetic interactions between the Fe ferromagnetic grains and the matrix. Finally, it is proposed that the existence of a molecular field of about 80 T originated by the penetration of the exchange field of α-Fe nanocrystals into the amorphous paramagnetic intergranular region is the main cause of this Curie temperature enhancement. Moreover, the compositional dependence of the Curie temperature in Fe-B-Nb-Cu amorphous ribbons has been reported.

The field-induced spin-density-wave state in (TMTSF${)}_2$${\mathrm{ClO}}_4$, where TMTSF is tetramethyltetraselenafulvalene, develops because the field diminishes the ‘‘antinesting’’ terms, ${\mathit{t}}_{\mathit{b}}^{\mathcal{’}}$, to restore the spin-density wave (SDW) that would exist at ${\mathit{t}}_{\mathit{b}}^{\mathcal{’}}$=0 despite the anion gap in ${\mathrm{ClO}}_4$. The gap changes the wave function’s symmetry for ‘‘nested’’ subbands—one of them changes sign upon crossing the new zone boundary, destroying the coherence of paired electrons at H≠0. Competition between the two phenomena leads to a reentrance of the metallic state. Magnetic breakdown is unable to restore a ${\mathrm{PF}}_6$-type ground state and reveals itself in a pattern of peaks for ${\mathit{T}}_{\mathrm{SDW}}$(H) periodic in ${\mathit{H}}^{\mathrm{-}1}$.

We have measured the temperature dependence of equal-time spin correlations in the quasi-one-dimensional S=1 antiferromagnet, Ni(${\mathrm{C}}_2$${\mathrm{H}}_8$${\mathrm{N}}_2$${)}_2$${\mathrm{NO}}_2$${\mathrm{ClO}}_4$ (NENP), by magnetic neutron scattering. The temperature dependence of the correlation length can be described as exponentially activated with an activation energy similar to the Haldane gaps in NENP.

The x-ray magnetic circular dichroism (XMCD) at the Fe and V 2p edge is measured in Fe/V multilayers. For a V 3 Å/Fe 4.4 Å multilayer, the induced V moment is at least 0.26${\mathrm{\mu }}_{\mathit{B}}$, and it is aligned antiferromagnetically with the Fe layers. The V dichroism signal is revealed to have a complicated structure relative to, e.g., the Fe dichroism signal. We estimate the orbital moment on the V to be 0.13${\mathrm{\mu }}_{\mathit{B}}$, similar to values seen in other ferromagnetic first-row transition metals. Only a lower bound for the V spin moment can be determined (0.13${\mathrm{\mu }}_{\mathit{B}}$), due to the breakdown of the XMCD spin ‘‘sum rule’’ in the case of V.

Electrical resistivity (ρ) and magnetic susceptibility (χ) were measured for single crystals of ${\mathrm{La}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Sr}}_{1+\mathit{x}}$${\mathrm{MnO}}_4$ (0.0≤x≤0.7), which were grown by the floating-zone method with varying the nominal hole concentration (x). With hole doping, critical temperature (${\mathit{T}}_{\mathit{N}}$) for the antiferromagnetic phase transition decreases and eventually a spin-glass phase appears for x≥0.2, perhaps due to the competition between the generic antiferromagnetic superexchange interaction and the ferromagnetic double-exchange interaction. At x≊1/2, real-space ordering of the doped holes occurs at ∼220 K, accompanying a steep increase of ρ as well as a suppression of χ.

Anisotropic superconducting flux-line behavior of single-crystal κ-[bis(ethylenedithio)tetrathiaful- valene${]}_2$Cu[N(CN${)}_2$]Br has been studied with dc magnetization and vibrating-reed (VR) techniques. A peak at ${\mathit{T}}^{\mathrm{*}}$(H) in the temperature dependence of the VR inverse quality factor 1/Q exhibits a shoulder for magnetic fields 0<${\mathrm{\mu }}_0$H≤0.5 T parallel to the conducting ac plane. The shoulder becomes unresolved near a kink in T*(H) at ${\mathrm{\mu }}_0$H≊0.7 T. Discontinuities in 1/Q and the VR frequency shift occur for 0.1≤${\mathrm{\mu }}_0$H≤1.3 T applied perpendicular to the ac plane and temperatures T≤20 K, well into the normal state. These anomalies are preliminary evidence for a field-induced magnetic phase transition and unconventional superconductivity.

The dynamics of the random-phase sine-Gordon model, which describes two-dimensional vortex-glass arrays and crystalline surfaces on disordered substrates, is investigated using the self-consistent Hartree approximation. The fluctuation-dissipation theorem is violated below the critical temperature ${\mathit{T}}_{\mathit{c}}$ for large time t≳${\mathit{t}}^{\mathrm{*}}$ where ${\mathit{t}}^{\mathrm{*}}$ diverges in the thermodynamic limit. While above ${\mathit{T}}_{\mathit{c}}$ the averaged autocorrelation function diverges as Tln(t), for T<${\mathit{T}}_{\mathit{c}}$ it approaches a finite value ${\mathit{q}}^{\mathrm{*}}$∼1/(${\mathit{T}}_{\mathit{c}}$-T) as q(t)=${\mathit{q}}^{\mathrm{*}}$-c(t/${\mathit{t}}^{\mathrm{*}}$${)}^{\mathrm{-}\nu }$ (for t→${\mathit{t}}^{\mathrm{*}}$) where ν is a temperature-dependent exponent. On larger time scales t≳${\mathit{t}}^{\mathrm{*}}$ the dynamics becomes nonergodic. The static correlations behave as ∼Tln‖x→‖ for T≳${\mathit{T}}_{\mathit{c}}$ and for T<${\mathit{T}}_{\mathit{c}}$ when x<${\xi }^{\mathrm{*}}$ with ${\xi }^{\mathrm{*}}$∼exp{A/(${\mathit{T}}_{\mathit{c}}$-T)}. For scales x≳${\xi }^{\mathrm{*}}$, they behave as ∼${\mathit{m}}^{\mathrm{-}1}$Tln‖x→‖ where m≊T/${\mathit{T}}_{\mathit{c}}$ near ${\mathit{T}}_{\mathit{c}}$, in general agreement with the variational replica-symmetry breaking approach and with recent simulations of the disordered-substrate surface. For strong coupling the transition becomes first order.

We report on the metallic ground state of the CuO chains in ${\mathrm{YBa}}_2$${\mathrm{Cu}}_4$${\mathrm{O}}_8$. The resistivities along the a and b directions have been determined for temperatures up to 900 K. Assuming a model of two shunted conduction channels along the b direction, representing the chain and plane resistivity, the resistivity of the chain ${\mathrm{\rho }}_{\mathrm{chain}}$ has been calculated. Below 300 K, ${\mathrm{\rho }}_{\mathrm{chain}}$∝${\mathit{T}}^2$ and approaches a ${\mathit{T}}^{4/3}$ temperature dependence above 500 K. At least above ${\mathit{T}}_{\mathit{c}}$, two different kinds of free carriers exist simultaneously: highly correlated charge carriers inside the ${\mathrm{CuO}}_2$ plane and itinerant electrons along the CuO chain.

We report on absolute ab-plane reflectivity measurements of the single-layer high-${\mathit{T}}_{\mathit{c}}$ superconductor ${\mathrm{Tl}}_2$${\mathrm{Ba}}_2$${\mathrm{CuO}}_{6+\mathrm{\delta }}$ in both the normal and superconducting states. The reflectivity has been measured from 40 to 40000 ${\mathrm{cm}}^{\mathrm{-}1}$ and the optical conductivity has been calculated from Kramers-Kronig analysis. The unusual form of the low-frequency reflectivity leads to an intense low-frequency feature in the optical conductivity. In the superconducting state, the spectral weight is strongly suppressed at frequencies below ∼800 ${\mathrm{cm}}^{\mathrm{-}1}$ due to the formation of a superfluid fraction. The value of the London penetration depth has been estimated to be 2400±200 Å, larger than that from muon-spin-resonance (μSR) experiments.

The anisotropic surface resistance ${\mathit{R}}_{\mathit{s}\mathrm{-}\mathit{ab}}$ and ${\mathit{R}}_{\mathit{s}\mathrm{-}\mathit{c}}$ as well as the penetration depth ${\lambda }_{\mathit{ab}}$ and ${\lambda }_{\mathit{c}}$ of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ single crystals have been measured at 9.6 GHz. ${\lambda }_{\mathit{c}}$(T) and ${\lambda }_{\mathit{ab}}$(T) are linear in temperature at low temperatures with much different slopes, consistent with the existence of line nodes on a cylindrical Fermi surface. A collapse of the c-axis scattering rate below ${\mathit{T}}_{\mathit{c}}$ is also observed, and the temperature dependence of the ab plane scattering rate is consistent with quasiparticle-quasiparticle scattering. The behavior of ${\lambda }_{\mathit{c}}$(T) is not consistent with proximity-effect models, or with cubic ${\mathit{d}}_{{\mathit{x}}^2+{\mathit{y}}^2\mathrm{-}{\mathit{z}}^2}$ pairing symmetry, but is consistent with a cubic ${\mathit{d}}_{{\mathit{x}}^2\mathrm{-}{\mathit{y}}^2}$ pairing state.

The collision of thermally excited ${\mathrm{C}}_{60}^{+}$ with a cross beam gas target of ${\mathrm{C}}_{60}$ clusters has been simulated employing the molecular-dynamics statistical-trajectory-ensemble method and the density functional theory linear combination of atomic orbitals local-density approximation. The time-resolved double-differential cross sections of the mass fragmentation and kinetic-energy angular distribution, and the mass-resolved fragment vibrational excitation and mean coordination number have been calculated with improved statistics from the newly available simulation data. The time-resolved double-differential cross sections show the causal order and other details of the fragmentation process. The fragmentation pattern of the small fragment sizes (N≤20) where this simulation has the most reliable statistics is given special attention.

The luminescent-channel efficiency for ${\mathrm{Ho}}^{3+}$ ions in ${\mathrm{HoLiF}}_4$ crystals was measured and compared with the case of ${\mathrm{Ho}}^{3+}$ as a low-concentration dopant (1.71%) in crystals of ${\mathrm{YLiF}}_4$. The ${}_{}{}^5{}_{}{}^{}$${\mathit{S}}_2$${\to }^5$${\mathit{I}}_7$, ${}_{}{}^5{}_{}{}^{}$${\mathit{I}}_8$ luminescent transitions are strongly quenched by two possible cross-relaxation processes: one with almost zero mismatch energy, favoring the population of the ${}_{}{}^5{}_{}{}^{}$${\mathit{I}}_5$, ${}_{}{}^5{}_{}{}^{}$${\mathit{I}}_6$, and ${}_{}{}^5{}_{}{}^{}$${\mathit{I}}_7$ levels, and the other, a laser transition ${}_{}{}^5{}_{}{}^{}$${\mathit{I}}_7$${\to }^5$${\mathit{I}}_8$ in the mid-infrared region. Also seen was a strong decrease of the total ${\mathrm{Ho}}^{3+}$ luminescence by approximately 6.6 times in ${\mathrm{HoLiF}}_4$ crystals from 10 to 300 K. This quenching effect was attributed to an energy transfer from the ${\mathrm{Ho}}^{3+}$ excited ${}_{}{}^5{}_{}{}^{}$${\mathit{I}}_6$ and ${}_{}{}^5{}_{}{}^{}$${\mathit{I}}_7$ levels to traps present in the crystal.

The rotator phase of ${\mathrm{C}}_{24}$${\mathrm{F}}_{50}$ has been characterized in its calorimetric as well as in its elastic properties. To perform the elastic characterization we took advantage of a polytetrafluoroethylene-induced-alignment crystal-growth technique. Special interest is paid to the rotator phase and the premelting behavior therein as reflected by the elastic stiffness coefficients ${\mathit{c}}_{33}$ and ${\mathit{c}}_{44}$. The anomalous elastic behavior is interpreted in the frame of the Landau theory. The premelting process is related to molecular conformational defects.

The frequency angular spectra of visible polarized light transmission through multiply domained ferroelectric ${\mathrm{KH}}_2$${\mathrm{PO}}_4$ have been studied. The spectra consist of alternating lines of intensity maxima. The relative intensity and frequency shift between the lines are sensitive to the variations of the domain structure. The known models of anisotropic diffraction by domain walls cannot explain the whole set of unusual characteristics obtained in the experiment, such as the high degree of spectrum regularity, large depolarization of light (up to 70%), and interference between the crossing lines. An interference polarization model is suggested: we consider the combination of transverse-longitudinal-transverse domain blocks with nonregular periodic structure. The analytic and computer simulations show the ability of this model to explain the effects observed in our experiment.