Hydrogen targets for exotic-nuclei studies developed over the past 10 years

Hydrogen-induced reactions provide essential information on nuclear structure, complementary to other experimental probes. For studies at both low and relativistic incident energy, developments in hydrogen targets have been performed over the past 10 years in parallel with the development of new radioactive beams. We present a review of all major hydrogen target developments related to the study of exotic nuclei with direct reactions in inverse kinematics. Both polarized and non-polarized systems are presented.Comment: 24 pages, 27 figures, review articl

Magnetic field dependence of the temperature derivative of resistivity: a probe for distinguishing the effects of pseudogap and superconducting fluctuations in cuprates

We have studied the magnetic field dependence of the temperature derivative of the resistivity, dr(H,T)/dT, of a number of Y1-xCaxBa2(Cu1-yZny)3O7-d crystalline thin films over a wide range of sample compositions. From the analysis of the temperature derivative data we have been able to distinguish quite clearly between two characteristic temperature scales, (a) the onset of strong superconducting fluctuation temperature, Tscf and (b) the pseudogap temperature, TPG. Significantly different characteristic features of dr(H,T)/dT at Tscf and at TPG imply that Tscf and TPG have different physical origins.Comment: Submitted to Physica C (M2S-HTSC 2006 Proceedings

Stripes, Non-Fermi-Liquid Behavior, and Two-Component Transport in the High-Tc Cuprates

Non-Fermi-liquid features of the high-Tc cuprates, and specifically the systematic behavior of the resistivity, Hall constant, and thermoelectric power, are shown to result from an electronic structure based on "large-U" and "small-U" orbitals, and the resulting striped structure.Comment: 3 pages including 3 figures, Late

Planar hole-doping concentration and effective three-dimensional hole-doping concentration for single-layer high-TcT_c superconductors

We propose that physical properties for the high temperature superconductors can be addressed by either a two-dimensional planar hole-doping concentration ($P_{pl}$) or an effective three-dimentional hole-doping concentration ($P_{3D}$). We find that superconducting transition temperature ($T_c$) exhibits a universal dome-shaped behavior in the $T_c$ $vs.$ $P_{3D}$ plot with a universal optimal doping concentration at $P_{3D}$ $\sim$ 1.6 $\times$ 10$^{21}$ cm$^{-3}$ for the single-layer high temperature superconductors.Comment: 2pages, 2 figures, submitted to Physica C (Proceedings of M2S-HTSC VIII) ; Ref. 10 is revise

Anomalous Fermi Liquid Behavior of Overdoped High-Tc Superconductors

According to a generic temperature vs. carrier-doping (T-p) phase diagram of high-temperature superconductors it has been proposed that as doping increases to the overdoped region they approach gradually a conventional (canonical) Fermi Liquid. However, Hall effect measurements in several systems reported by different authors show a still strong \emph{T}-dependence in overdoped samples. We report here electrical transport measurements of Y_{1-x}Ca_{x}Ba_{2}Cu_{3}O_{7-delta} thin films presenting a temperature dependence of the Hall constant, R_H, which does not present a gradual transition towards the T-independent behavior of a canonical Fermi Liquid. Instead, the T-dependence passes by a minimum near optimal doping and then increases again in the overdoped region. We discuss the theoretical predictions from two representative Fermi Liquid models and show that they can not give a satisfactory explanation to our data. We conclude that this region of the phase diagram in YBCO, as in most HTSC, is not a canonical Fermi Liquid, therefore we call it Anomalous Fermi Liquid.Comment: 9 pages, 12 figures, to be published in Phys. Rev.

Effects of Zn on the grain boundary properties of La2-xSrxCu1-yZnyO4 superconductors

The properties of the grain boundaries (GBs) are of significant importance in high-Tc cuprates. Most large scale applications of cuprate superconductors involve usage of sintered compounds. The critical current density and the ability to trap high magnetic flux inside the sample depend largely on the quality of the GBs. Zn has the ability to pin vortices but it also degrades superconductivity. In this study we have investigated the effect of Zn impurity on the intergrain coupling properties in high-quality La2-xSrxCu1-yZnyO4 sintered samples with different hole concentrations, p (\equiv x), over a wide range of Zn contents (y) using field-dependent ac susceptibility (ACS) measurements. The ACS results enabled us to determine the superconducting transition temperature Tc, and the temperature Tgcp, at which the randomly oriented superconducting grains become coupled as a function of hole and disorder contents. We have analyzed the behavior of the GBs from the systematic evolution of the values of Tgcp(p, y), Tc(p, y), and from the contribution to the field-dependent ACS signal coming from the intergrain shielding current. Zn suppresses both Tc and Tgcp in a similar fashion. The hole content and the carrier localization due to Zn substitution seem to have significant effect on the coupling properties of the GBs. We have discussed the possible implications of these findings in detail in this article. PACS: 74.72.Dn; 74.62.Dh; 74.25.Sv Keywords: Zn doped La214; Critical current density; Grain boundaryComment: To appear in Physica

Stripe Fluctuations, Carriers, Spectroscopies, Transport, and BCS-BEC Crossover in the High-T_c Cuprates

The quasiparticles of the high-T_c cuprates are found to consist of: polaron-like "stripons" carrying charge, and associated primarily with large-U orbitals in stripe-like inhomogeneities; "quasielectrons" carrying charge and spin, and associated with hybridized small-U and large-U orbitals; and "svivons" carrying spin and lattice distortion. It is shown that this electronic structure leads to the systematic behavior of spectroscopic and transport properties of the cuprates. High-T_c pairing results from transitions between pair states of stripons and quasielectrons through the exchange of svivons. The cuprates fall in the regime of crossover between BCS and preformed-pairs Bose-Einstein condensation behaviors.Comment: Latex file, 8 pages (new version including a figure

Effects of next-nearest-neighbor hopping t′t^{\prime} on the electronic structure of cuprates

Photoemission spectra of underdoped and lightly-doped Bi$_{2-z}$Pb$_z$Sr$_2$Ca$_{1-x}${\it R}$_{x}$Cu$_2$O$_{8+y}$ ($R=$ Pr, Er) (BSCCO) have been measured and compared with those of La$_{2-x}$Sr$_x$CuO$_4$ (LSCO). The lower-Hubbard band of the insulating BSCCO, like Ca$_2$CuO$_2$Cl$_2$, shows a stronger dispersion than La$_2$CuO$_4$ from ${\bf k}\sim$($\pi/2,\pi/2$) to $\sim$($\pi,0$). The flat band at ${\bf k}\sim$($\pi,0$) is found generally deeper in BSCCO. These observations together with the Fermi-surface shapes and the chemical potential shifts indicate that the next-nearest-neighbor hopping $|t^{\prime}|$ of the single-band model is larger in BSCCO than in LSCO and that $|t^{\prime}|$ rather than the super-exchange $J$ influences the pseudogap energy scale.Comment: 5 pages,4 figures, 1 tabl

Carrier concentrations in Bi_{2}Sr_{2-z}La_{z}CuO_{6+\delta} single crystals and their relation to Hall coefficient and thermopower

We measured the thermopower S and the Hall coefficients R_H of Bi_{2}Sr_{2-z}La_{z}CuO_{6+\delta} (BSLCO) single crystals in a wide doping range, in an effort to identify the actual hole concentrations per Cu, p, in this system. It is found that the "universal" relation between the room-temperature thermopower and T_c does not hold in the BSLCO system. Instead, comparison of the temperature-dependent R_H data with other cuprate systems is used as a tool to identify the actual p value. To justify this approach, we compare normalized R_H(T) data of BSLCO, La_{2-x}Sr_{x}CuO_{4} (LSCO), YBa_{2}Cu_{3}O_{y}, and Tl_{2}Ba_{2}CuO_{6+\delta}, and demonstrate that the R_H(T) data of the LSCO system can be used as a template for the estimation of p. The resulting phase diagram of p vs T_c for BSLCO suggests that T_c is anomalously suppressed in the underdoped samples, becoming zero at around p ~ 0.10, while the optimum T_c is achieved at p ~ 0.16 as expected.Comment: 4 pages including 5 figures, accepted for publication in Phys. Rev. B, Rapid Communication

XCDCC: Core Excitation in the Breakup of Exotic Nuclei

The eXtended Continuum Discretized Coupled Channel (XCDCC) method is developed to treat reactions where core degrees of freedom play a role. The projectile is treated as a multi-configuration coupled channels system generated from a valence particle coupled to a deformed core which is allowed to excite. The coupled channels initial state breaks up into a coupled channels continuum which is discretized into bins, similarly to the original CDCC method. Core collective degrees of freedom are also included in the interaction of the core and the target, so that dynamical effects can occur during the reaction. We present results for the breakup of $^{17}$C=$^{16}$C+n and $^{11}$Be=$^{10}$Be+n on $^{9}$Be. Results show that the total cross section increases with core deformation. More importantly, the relative percentage of the various components of the initial state are modified during the reaction process through dynamical effects. This implies that comparing spectroscopic factors from structure calculations with experimental cross sections requires more detailed reaction models that go beyond the single particle model.Comment: 14 pages, revtex, submitted to Phys Rev