Search

We conducted measurements of $K^- + {^3{\rm He}} \to \pi \!Y \!N + N'$ reactions using a $1~{\rm GeV}/c$ $K^-$-beam, with the objective of understanding the broad decay width of $\bar{K} \!N \!N$ (approximately twice as broad as that of $\Lambda(1405)$ considered to be the $\bar{K} \!N$ quasi-bound state). We successfully reproduced distributions of the $\pi \! Y \! N$ invariant mass and momentum transfer for $\pi \! Y \! N$ using model fitting functions for $\bar{K} \!N \!N$ formation and quasi-free $\bar{K}$ absorption (${\rm QF}_{\bar{K}-{\rm abs}}$) processes. The model can describe the experimental data quite well, and four $\bar{K} \! N \! N \to \pi \! Y \! N $ cross-sections were obtained. The results indicate that mesonic decay is the dominant decay branch of $\bar{K} \! N \! N$. The results also suggest that $\Gamma_{\pi \Lambda N} \sim \Gamma_{\pi \Sigma N}$, which indicates that the $I_{\bar{K} \! N}=1$ absorption channel, in addition to the $I_{\bar{K} \! N}=0$ absorption channel, substantially contribute to the $\bar{K} \! N \! N$ decay, making the $\bar{K} \! N \! N$ state approximately twice as unstable as $\Lambda$(1405).

Metal tubes plated with nickel-phosphorus are used in many fundamental physics experiments using ultracold neutrons (UCN) because of their ease of fabrication. These tubes are usually polished to a average roughness of 25-150 nm. However, there is no scattering model that accurately describes UCN scattering on such a rough guide surface with a mean-square roughness larger than 5 nm. We therefore developed a scattering model for UCN in which scattering from random surface waviness with a size larger than the UCN wavelength is described by a microfacet Bidirectional Reflectance Distribution Function model (mf-BRDF model), and scattering from smaller structures by the Lambert's cosine law (Lambert model). For the surface waviness, we used the statistical distribution of surface slope measured by an atomic force microscope on a sample piece of guide tube as input of the model. This model was used to describe UCN transmission experiments conducted at the pulsed UCN source at J-PARC. In these experiments, a UCN beam collimated to a divergence angle smaller than $\pm 6^{\circ}$ was directed into a guide tube with a mean-square roughness of 6.4 nm to 17 nm at an oblique angle, and the UCN transport performance and its time-of-flight distribution were measured while changing the angle of incidence. The mf-BRDF model combined with the Lambert model with scattering probability $p_{L} = 0.039\pm0.003$ reproduced the experimental results well. We have thus established a procedure to evaluate the characteristics of UCN guide tubes with a surface roughness of approximately 10 nm., Comment: 15 pages, 11 figures. Accepted for publication in PRC

We measured a set of $\pi^\pm\Sigma^\mp$, $\pi^0\Sigma^0$, and $\pi^-\Sigma^0$ invariant mass spectra below and above the $\bar{K}N$ mass threshold in $K^-$-induced reactions on deuteron. We deduced the $S$-wave $\bar{K}N\rightarrow\pi\Sigma$ and $\bar{K}N\rightarrow\bar{K}N$ scattering amplitudes in the isospin 0 channel in the framework of a $\bar{K}N$ and $\pi\Sigma$ coupled channel. We find that a resonance pole corresponding to $\Lambda(1405)$ is located at 1417.7$^{+6.0}_{-7.4}$(fitting errors)$^{+1.1}_{-1.0}$(systematic errors) + $[-26.1^{+6.0}_{-7.9}$(fitting errors)$^{+1.7}_{-2.0}$(systematic errors)]$i$ MeV/$c^2$, closer to the $\bar{K}N$ mass threshold than the value determined by the Particle Data Group., Comment: 8 pages, 5 figures

Electroless nickel plating is an established industrial process that provides a robust and relatively low-cost coating suitable for transporting and storing ultracold neutrons (UCN). Using roughness measurements and UCN-storage experiments we characterized UCN guides made from polished aluminum or stainless-steel tubes plated by several vendors. All electroless nickel platings were similarly suited for UCN storage with an average loss probability per wall bounce of $2.8\cdot10^{-4}$ to $4.1\cdot10^{-4}$ for energies between 90 neV and 190 neV, or a ratio of imaginary to real Fermi potential $\eta$ of $1.7\cdot10^{-4}$ to $3.3\cdot10^{-4}$. Measurements at different elevations indicate that the energy dependence of UCN losses is well described by the imaginary Fermi potential. Some special considerations are required to avoid an increase in surface roughness during the plating process and hence a reduction in UCN transmission. Increased roughness had only a minor impact on storage properties. Based on these findings we chose a vendor to plate the UCN-production vessel that will contain the superfluid-helium converter for the new TRIUMF UltraCold Advanced Neutron (TUCAN) source, achieving acceptable UCN-storage properties with ${\eta=3.5(5)\cdot10^{-4}}$., Comment: 8 pages, 7 figures

$\bar K$-nuclear bound systems, kaonic nuclei, have been widely discussed as products of the strongly attractive $\bar K N$ interaction in $I = 0$ channels. Recently, we demonstrated that kaonic nuclei can be produced via in-flight $(K^-,N)$ reactions using the low-momentum DC kaon beam at the J-PARC E15 experiment. We observed the simplest kaonic nuclei, $K^-pp$, having a much deeper binding energy than normal nuclei. For further studies, we have proposed a series of experimental programs for the systematic investigation of light kaonic nuclei, from $\bar K N$ ($\Lambda(1405)$) to $\bar K NNNN$. In the new experiment approved as J-PARC E80, we will measure the $\bar K NNN$ ($A=3$) system as a first step toward a comprehensive study., Comment: 10 pages, 5 figures, proceedings of the 8th Asia-Pacific Conference on Few-Body Problems in Physics (APFB2020), accepted for publication in Fwe-Body Systems

Five transport coefficients of the cuprate superconductor Bi$_2$Sr$_{2-x}$La$_x$CuO$_{6+\delta}$ were measured in the normal state down to low temperature, reached by applying a magnetic field (up to 66T) large enough to suppress superconductivity. The electrical resistivity, Hall coefficient, thermal conductivity, Seebeck coefficient and thermal Hall conductivity were measured in two overdoped single crystals, with La concentration $x = 0.2$ ($T_{\rm c}=18$K) and $x = 0.0$ ($T_{\rm c}=10$K). The samples have dopings $p$ very close to the critical doping $p^{\star}$ where the pseudogap phase ends. The resistivity displays a linear dependence on temperature whose slope is consistent with Planckian dissipation. The Hall number $n_{\rm H}$ decreases with reduced $p$, consistent with a drop in carrier density from $n = 1+p$ above $p^{\star}$ to $n=p$ below $p^{\star}$. This drop in $n_{\rm H}$ is concomitant with a sharp drop in the density of states inferred from prior NMR Knight shift measurements. The thermal conductivity satisfies the Wiedemann-Franz law, showing that the pseudogap phase at $T = 0$ is a metal whose fermionic excitations carry heat and charge as do conventional electrons. The Seebeck coefficient diverges logarithmically at low temperature, a signature of quantum criticality. The thermal Hall conductivity becomes negative at low temperature, showing that phonons are chiral in the pseudogap phase. Given the observation of these same properties in other, very different cuprates, our study provides strong evidence for the universality of these five signatures of the pseudogap phase and its critical point., Comment: Added references

We have performed an exclusive measurement of the $K^{-}+\! ~^{3}{\rm He} \to \Lambda pn$ reaction at an incident kaon momentum of $1\ {\rm GeV}/c$.In the $\Lambda p$ invariant mass spectrum, a clear peak was observed below the mass threshold of $\bar{K}\!+\!N\!+\!N$, as a signal of the kaonic nuclear bound state, $\bar{K}NN$.The binding energy, decay width, and $S$-wave Gaussian reaction form-factor of this state were observed to be $B_{K} = 42\pm3({\rm stat.})^{+3}_{-4}({\rm syst.})\ {\rm MeV}$, $\Gamma_{K} = 100\pm7({\rm stat.})^{+19}_{-9}({\rm syst.})\ {\rm MeV}$, and $Q_{K} = 383\pm11({\rm stat.})^{+4}_{-1}({\rm syst.})\ {\rm MeV}/c$, respectively. The total production cross-section of $\bar{K}NN$, determined by its $\Lambda p$ decay mode, was $\sigma^{tot}_{K} \cdot BR_{\Lambda p} = 9.3\pm0.8({\rm stat.})^{+1.4}_{-1.0}({\rm syst.})\ \mu{\rm b}$.We estimated the branching ratio of the $\bar{K}NN$ state to the $\Lambda p$ and $\Sigma^{0}p$ decay modes as $BR_{\Lambda p}/BR_{\Sigma^{0}p} \sim 1.7$, by assuming that the physical processes leading to the $\Sigma N\!N$ final states are analogous to those of $\Lambda pn$., Comment: 13 pages, 12 figures

We report on our efforts to optimize the geometry of neutron moderators and converters for the TRIUMF UltraCold Advanced Neutron (TUCAN) source using MCNP simulations. It will use an existing spallation neutron source driven by a 19.3 kW proton beam delivered by TRIUMF's 520 MeV cyclotron. Spallation neutrons will be moderated in heavy water at room temperature and in liquid deuterium at 20 K, and then superthermally converted to ultracold neutrons in superfluid, isotopically purified $^4$He. The helium will be cooled by a $^3$He fridge through a $^3$He-$^4$He heat exchanger. The optimization took into account a range of engineering and safety requirements and guided the detailed design of the source. The predicted ultracold-neutron density delivered to a typical experiment is maximized for a production volume of 27 L, achieving a production rate of $1.4 \cdot 10^7$ s$^{-1}$ to $1.6 \cdot 10^7$ s$^{-1}$ with a heat load of 8.1 W. At that heat load, the fridge can cool the superfluid helium to 1.1 K, resulting in a storage lifetime for ultracold neutrons in the source of about 30 s. The most critical performance parameters are the choice of cold moderator and the volume, thickness, and material of the vessel containing the superfluid helium. The source is scheduled to be installed in 2021 and will enable the TUCAN collaboration to measure the electric dipole moment of the neutron with a sensitivity of $10^{-27}$ e cm.

A fast-switching, high-repetition-rate magnet and power supply have been developed for and operated at TRIUMF, to deliver a proton beam to the new ultracold neutron (UCN) facility. The facility possesses unique operational requirements: a time-averaged beam current of 40~$\mu$A with the ability to switch the beam on or off for several minutes. These requirements are in conflict with the typical operation mode of the TRIUMF cyclotron which delivers nearly continuous beam to multiple users. To enable the creation of the UCN facility, a beam-sharing arrangement with another facility was made. The beam sharing is accomplished by the fast-switching (kicker) magnet which is ramped in 50~$\mu$s to a current of 193~A, held there for approximately 1~ms, then ramped down in the same short period of time. This achieves a 12~mrad deflection which is sufficient to switch the proton beam between the two facilities. The kicker magnet relies on a high-current, low-inductance coil connected to a fast-switching power supply that is based on insulated-gate bipolar transistors (IGBTs). The design and performance of the kicker magnet system and initial beam delivery results are reported., Comment: 16 pages, 21 figures

This article describes the new primary proton beamline 1U at TRIUMF. The purpose of this beamline is to produce ultracold neutrons (UCN) for fundamental-physics experiments. It delivers up to 40 microA of 480 MeV protons from the TRIUMF cyclotron to a tungsten spallation target and uses a fast kicker to share the beam between the Center for Molecular and Materials Science and UCN. The beamline has been successfully commissioned and operated with a beam current up to 10 microA, facilitating first large-scale UCN production in Canada.

We installed a source for ultracold neutrons at a new, dedicated spallation target at TRIUMF. The source was originally developed in Japan and uses a superfluid-helium converter cooled to 0.9$\,$K. During an extensive test campaign in November 2017, we extracted up to 325000 ultracold neutrons after a one-minute irradiation of the target, over three times more than previously achieved with this source. The corresponding ultracold-neutron density in the whole production and guide volume is 5.3$\,$cm$^{-3}$. The storage lifetime of ultracold neutrons in the source was initially 37$\,$s and dropped to 24$\,$s during the eighteen days of operation. During continuous irradiation of the spallation target, we were able to detect a sustained ultracold-neutron rate of up to 1500$\,$s$^{-1}$. Simulations of UCN production, UCN transport, temperature-dependent UCN yield, and temperature-dependent storage lifetime show excellent agreement with the experimental data and confirm that the ultracold-neutron-upscattering rate in superfluid helium is proportional to $T^7$., Comment: 8 pages, 10 figures

We observed a distinct peak in the $\Lambda p$ invariant mass spectrum of $^{3}{\rm He}(K^-, \, \Lambda p)n$, well below the mass threshold of $m_K + 2 m_p$. By selecting a relatively large momentum-transfer region $q = 350 \sim 650$ MeV/$c$, one can clearly separate the peak from the quasi-free process, $\overline{K}N \rightarrow \overline{K}N$ followed by the non-resonant absorption by the two spectator-nucleons $\overline{K}NN \rightarrow \Lambda N $. We found that the simplest fit to the observed peak gives us a Breit-Wigner pole position at $B_{\rm {\it Kpp}} = 47 \pm 3 \, (stat.) \,^{+3}_{-6} \,(sys.)$ MeV having a width $\Gamma_{\rm {\it Kpp}} = 115 \pm 7 \, (stat.) \,^{+10}_{-9} \,(sys.)$ MeV, and the $S$-wave Gaussian reaction form-factor parameter $Q_{\rm {\it Kpp}} = 381 \pm 14 \, (stat.)\,^{+57}_{-0} \,(sys.)$ MeV/$c$, as a new form of the nuclear bound system with strangeness -- "$K^-pp$"., Comment: 17 pages, 4 figures

Superconductivity appears in the cuprates when a spin order is destroyed, while the role of charge is less known. Recently, charge density wave (CDW) was found below the superconducting dome in YBa$_2$Cu$_3$O$_y$ when a high magnetic field is applied perpendicular to the CuO$_2$ plane, which was suggested to arise from incipient CDW in the vortex cores that becomes overlapped. Here, by $^{63}$Cu-nuclear magnetic resonance, we report the discovery of CDW induced by an in-plane field that does not create vortex cores in the plane, setting in above the dome in single-layered Bi$_2$Sr$_{2-x}$La$_x$CuO$_6$.The onset temperature $T_{\rm CDW}$ takes over the antiferromagnetic order temperature $T_{\rm N}$ beyond a critical doping level at which superconductivity starts to emerge, and scales with the psudogap temperature $T^{*}$. These results provide important insights into the relationship between spin order, CDW and the pseudogap, and their connections to high-temperature superconductivity., Comment: 22 pages, 8 figures

To search for an S= -1 di-baryonic state which decays to $\Lambda p$, the $ {\rm{}^3He}(K^-,\Lambda p)n_{missing}$ reaction was studied at 1.0 GeV/$c$. Unobserved neutrons were kinematically identified from the missing mass $M_X$ of the $ {\rm{}^3He}(K^-,\Lambda p)X$ reaction in order to have a large acceptance for the $\Lambda pn$ final state. The observed $\Lambda p n$ events, distributed widely over the kinematically allowed region of the Dalitz plot, establish that the major component comes from a three nucleon absorption process. A concentration of events at a specific neutron kinetic energy was observed in a region of low momentum transfer to the $\Lambda p$. To account for the observed peak structure, the simplest S-wave pole was assumed to exist in the reaction channel, having Breit-Wigner form in energy and with a Gaussian form-factor. A minimum $\chi^2$ method was applied to deduce its mass $M_X\ =$ 2355 $ ^{+ 6}_{ - 8}$ (stat.) $ \pm 12$ (syst.) MeV/c$^2$, and decay-width $\Gamma_X\ = $ 110 $ ^{+ 19}_{ - 17}$ (stat.) $ \pm 27$ (syst.) MeV/c$^2$, respectively. The form factor parameter $Q_X \sim$ 400 MeV/$c$ implies that the range of interaction is about 0.5, Comment: 12pages, 8 figures

The antikaon-nucleon interaction close to threshold provides crucial information on the interplay between spontaneous and explicit chiral symmetry breaking in low-energy QCD. In this context the importance of kaonic deuterium X-ray spectroscopy has been well recognized, but no experimental results have yet been obtained due to the difficulty of the measurement. We propose to measure the shift and width of the kaonic deuterium 1s state with an accuracy of 60 eV and 140 eV respectively at J-PARC. These results together with the kaonic hydrogen data (KpX at KEK, DEAR and SIDDHARTA at DAFNE) will then permit the determination of values of both the isospin I=0 and I=1 antikaon-nucleon scattering lengths and will provide the most stringent constraints on the antikaon-nucleon interaction, promising a breakthrough. Refined Monte Carlo studies were performed, including the investigation of background suppression factors for the described setup. These studies have demonstrated the feasibility of determining the shift and width of the kaonic deuterium atom 1s state with the desired accuracy of 60 eV and 140 eV., Comment: 12 pages, 9 figures

Ultracold neutrons (UCNs) can be bound by the potential of terrestrial gravity and a reflecting mirror. The wave function of the bound state has characteristic modulations. We carried out an experiment to observe the vertical distribution of the UCNs above such a mirror at Institut Laue-Langevin in 2011. The observed modulation is in good agreement with that prediction by quantum mechanics using the Wigner function. The spatial resolution of the detector system is estimated to be 0.7 micro meter. This is the first observation of gravitationally bound states of UCNs with submicron spatial resolution., Comment: 5 pages, 3 figures

We report a systematic study by 75As nuclear-quadrupole resonance in LaFeAsO1-xFx. The antiferromagnetic spin fluctuation (AFSF) found above the magnetic ordering temperature TN = 58 K for x = 0.03 persists in the regime 0.04 < x < 0.08 where superconductivity sets in. A dome-shaped x-dependence of the superconducting transition temperature Tc is found, with the highest Tc = 27 K at x = 0.06 which is realized under significant AFSF. With increasing x further, the AFSF decreases, and so does Tc. These features resemble closely the cuprates La2-xSrxCuO4. In x = 0.06, the spin-lattice relaxation rate (1/T1) below Tc decreases exponentially down to 0.13 Tc, which unambiguously indicates that the energy gaps are fully-opened. The temperature variation of 1/T1 below Tc is rendered nonexponential for other x by impurity scattering., Comment: 5 pages, 5 figures, more references added

We present extensive 75As NMR and NQR data on the superconducting arsenides PrFeAs0.89F0.11 (Tc=45 K), LaFeAsO0.92F0.08 (Tc=27 K), LiFeAs (Tc = 17 K) and Ba0.72K0.28Fe2As2 (Tc = 31.5 K) single crystal, and compare with the nickel analog LaNiAsO0.9F0.1 (Tc=4.0 K) . In contrast to LaNiAsO0.9F0.1 where the superconducting gap is shown to be isotropic, the spin lattice relaxation rate 1/T1 in the Fe-arsenides decreases below Tc with no coherence peak and shows a step-wise variation at low temperatures. The Knight shift decreases below Tc and shows a step-wise T variation as well. These results indicate spinsinglet superconductivity with multiple gaps in the Fe-arsenides. The Fe antiferromagnetic spin fluctuations are anisotropic and weaker compared to underdoped copper-oxides or cobalt-oxide superconductors, while there is no significant electron correlations in LaNiAsO0.9F0.1. We will discuss the implications of these results and highlight the importance of the Fermi surface topology., Comment: 6 pages, 11 figures

We report systematic ^{75}As-NQR and ^{139}La-NMR studies on nickel-pnictide superconductors LaNiAsO_{1-x}F_x (x=0, 0.06, 0.10 and 0.12). The spin lattice relaxation rate 1/T_1 decreases below T_c with a well-defined coherence peak and follows an exponential decay at low temperatures. This result indicates that the superconducting gap is fully opened, and is strikingly different from that observed in iron-pnictide analogs. In the normal state, 1/T_1T is constant in the temperature range T_c \sim 4 K < T <10 K for all compounds and up to T=250 K for x=0 and 0.06, which indicates weak electron correlations and is also different from the iron analog. We argue that the differences between the iron and nickel pnictides arise from the different electronic band structure. Our results highlight the importance of the peculiar Fermi-surface topology in iron-pnictides., Comment: 4 pages, 5 figures

75As-zero-field nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements are performed on CaFe2As2 under pressure. At P = 4.7 and 10.8 kbar, the temperature dependences of nuclear-spin-lattice relaxation rate (1/T1) measured in the tetragonal phase show no coherence peak just below Tc(P) and decrease with decreasing temperature. The superconductivity is gapless at P = 4.7 kbar but evolves to that with multiple gaps at P = 10.8 kbar. We find that the superconductivity appears near a quantum critical point under pressures in the range 4.7 kbar < P < 10.8 kbar. Both electron correlation and superconductivity disappear in the collapsed tetragonal phase. A systematic study under pressure indicates that electron correlations play a vital role in forming Cooper pairs in this compound., Comment: 5pages, 5figures

A pixel detector with high spatial resolution and temporal information for ultra-cold neutrons is developed based on a commercial CCD on which a neutron converter is attached. 10B and 6Li are tested for the neutron converter and 10B is found to be more suitable based on efficiency and spatial resolution. The pixel detector has an efficiency of 44.1 +- 1.1% and a spatial resolution of 2.9 +- 0.1 um (1 sigma)., Comment: Accepted for publication in NIMA, 19 pages, 11 figure

We report ^{11}B NMR measurements in non-centrosymmetric superconductors Mg_{9.3}Ir_{19}B_{16.7} (T_c=5.8 K) and Mg_{10.5}Ir_{19}B_{17.1} (T_c=4.8 K). The spin lattice relaxation rate and the Knight shift indicate that the Cooper pairs are predominantly in the spin-singlet state with an isotropic gap. However, Mg_{10.5}Ir_{19}B_{17.1} is found to have more defects and the spin susceptibility remains finite even in the zero-temperature limit. We interpret this result as that the defects enhance the spin-orbit coupling and bring about more spin-triplet component., Comment: for a proper, high-resolution Fig.5, contact the corresponding author

CoO2 is the parent compound for the superconductor NaxCoO2\cdot1.3H2O and was widely believed to be a Mott insulator. We performed 59Co nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) studies on LixCoO2 (x = 0.35, 0.25, 0.12, and 0.0) to uncover the electronic state and spin correlations in this series of compounds which was recently obtained through electrochemical de-intercalation of Li from pristine LiCoO2. We find that although the antiferromagnetic spin correlations systematically increase with decreasing Li-content (x), the end member, CoO2 is a non-correlated metal that well satisfies the Korringa relation for a Fermi liquid. Thus, CoO2 is not simply located at the limit of x->0 for AxCoO2 (A = Li, Na) compounds. The disappearance of the electron correlations in CoO2 is due to the three dimensionality of the compound which is in contrast to the highly two dimensional structure of AxCoO2., Comment: 4pages, 4figures, to be published in Phys.Rev.B. Rapids

An experimental setup is proposed for the precise measurement of the quantum states of ultracold neutrons bound in the earth's gravitational field. The experiment utilizes a CCD-based pixel sensor and magnification system to observe the fine structure of the neutron distribution. In this work, we analyzed the sensor's deposited energy measurement capability and found that its spatial resolution was 5.3 um. A magnifying power of two orders of magnitude was realized by using a cylindrical rod as a convex mirror., Comment: Accepted for publication in NIMA; 13 pages, 8 figures

We report $^{75}$As nuclear quadrupole resonance (NQR) studies on superconducting oxypnictide LaFeAsO$_{0.92}$F$_{0.08}$ ($T_{\rm c}$ = 23 K). The temperature dependence of the spin lattice relaxation rate (1/$T_1$) decreases below $T_{\rm c}$ without a coherence (Hebel-Slichter) peak and shows a temperature dependence that is not simple power-law nor exponential. We show that the result can be understood in terms of two superconducting gaps of either $d$- or ${\pm}s$-wave symmetry, with the larger gap $\Delta_1\sim 4 k_{\rm B}T_{\rm c}$ and the smaller one $\Delta_2 \sim 1.5 k_{\rm B}T_{\rm c}$. Our result suggests that the multiple-gaps feature is universal in the oxypnictides superconductors, which is probably associated with the multiple electronic bands structure in this new class of materials. We also find that 1/$T_1T$ above $T_{\rm c}$ increases with decreasing temperature, which suggests weak magnetic fluctuations in the normal state., Comment: 4pages, 4figures, accepted for publication in Phys. Rev. B (rapid Communication)

We report $^{123}$Sb nuclear quadrupole resonance (NQR) measurements of the filled skutterudite heavy-fermion superconductor PrOs$_4$Sb$_{12}$ under high pressure. The temperature dependence of NQR frequency and the spin-lattice relaxation rate $1/T_1$ indicate that the crystal-electric-field splitting $\Delta_{\rm CEF}$ between the ground state $\Gamma_1$ singlet and the first excited state $\Gamma_4^{(2)}$ triplet decreases with increasing pressure. Ac-susceptibility measurements indicate that the superconducting transition temperature ($T_{\rm c}$) also decreases with increasing pressure. However, above $P$ $\sim$ 2 GPa, both $\Delta_{\rm CEF}$ and $T_{\rm c}$ do not depend on external pressure up to $P$ = 3.82 GPa. These pressure dependences of $\Delta_{\rm CEF}$ and $T_{\rm c}$ suggest an intimate relationship between quadrupole excitations associated with the $\Gamma_4^{(2)}$ level and unconventional superconductivity in PrOs$_4$Sb$_{12}$. In the superconducting state, 1/$T_1$ below $T_{\rm c}$ = 1.55 and 1.57 K at $P$ = 1.91 and 2.63 GPa shows a power-law temperature variations and are proportional to $T^5$ at temperatures considerably below $T_{\rm c}$. These data can be well fitted by the gap model $\Delta(\theta) = \Delta_0\sin\theta$ with $\Delta_0$ = 3.08 $k_{\rm B}T_{\rm c}$ and 3.04 $k_{\rm B}T_{\rm c}$ for $P$ = 1.91 and 2.63 GPa, respectively. The results indicate there exists point nodes in the gap function., Comment: 6pages, 9figures

We report on the pressure-induced unconventional superconductivity in the heavy-fermion antiferromagnet CeIn3 by means of nuclear-quadrupole-resonance (NQR) studies conducted under a high pressure. The temperature and pressure dependences of the NQR spectra have revealed a first-order quantum-phase transition (QPT) from an AFM to PM at a critical pressure Pc=2.46 GPa. Despite the lack of an AFM quantum critical point in the P-T phase diagram, we highlight the fact that the unconventional SC occurs in both phases of the AFM and PM. The nuclear spin-lattice relaxation rate 1/T1 in the AFM phase have provided evidence for the uniformly coexisting AFM+SC phase. In the HF-PM phase where AFM fluctuations are not developed, 1/T1 decreases without the coherence peak just below Tc, followed by a power-law like T dependence that indicates an unconventional SC with a line-node gap. Remarkably, Tc has a peak around Pc in the HF-PM phase as well as in the AFM phase. In other words, an SC dome exists with a maximum value of Tc = 230 mK around Pc, indicating that the origin of the pressure-induced HF SC in CeIn3 is not relevant to AFM spin fluctuations but to the emergence of the first-order QPT in CeIn3. When the AFM critical temperature is suppressed at the termination point of the first-order QPT, Pc = 2.46 GPa, the diverging AFM spin-density fluctuations emerge at the critical point from the AFM to PM. The results with CeIn3 leading to a new type of quantum criticality deserve further theoretical investigations.

We report T_c and ^{59}Co nuclear quadrupole resonance (NQR) measurements on the cobalt oxide superconductor Na_{x}CoO_{2}\cdot 1.3H_{2}O (T_c=4.8 K) under hydrostatic pressure (P) up to 2.36 GPa. T_c decreases with increasing pressure at an average rate of -0.49\pm0.09 K/GPa. At low pressures P\leq0.49 GPa, the decrease of T_c is accompanied by a weakening of the spin correlations at a finite wave vector and a reduction of the density of states (DOS) at the Fermi level. At high pressures above 1.93 GPa, however, the decrease of T_c is mainly due to a reduction of the DOS. These results indicate that the electronic/magnetic state of Co is primarily responsible for the superconductivity. The spin-lattice relaxation rate 1/T_1 at P=0.49 GPa shows a T^3 variation below T_c down to T\sim 0.12T_c, which provides compelling evidence for the presence of line nodes in the superconducting gap function., Comment: published on 19, Sept. 2007 on Phys. Rev. B

The International Roadmap for Ferroelectric Memories requires three-dimensional integration of high-dielectric materials onto metal interconnects or bottom electrodes by 2010. We report the first integration of high-dielectric oxide films onto carbon nanotube electrodes with an aim of ultra-high integration density of FeRAMs (Tb/in2)., Comment: 4 pages, 3 figures