New Luttinger-liquid physics from photoemission on Li0.9M06O17

Temperature dependent high resolution photoemission spectra of quasi-one-dimensional Li(0.9)Mo(6)O(17)evince a strong renormalization of its Luttinger-liquid density-of-states anomalous exponent. We trace this new effect to interacting charge neutral critical modes that emerge naturally from the two-band nature of the material. Li(0.9)Mo(6)O(17) is shown thereby to be a paradigm material that is capable of revealing new Luttinger physics.     

Giant Nernst effect and bipolarity in the quasi-one-dimensional metal Li0.9Mo6O17

The Nernst coefficient for the quasi-one-dimensional metal, Li{0.9}Mo{6}O{17}, is found to be among the largest known for metals (ν?500 μV/KT at T～20 K), and is enhanced in a broad range of temperature by orders of magnitude over the value expected from Boltzmann theory for carrier diffusion. A comparatively small Seebeck coefficient implies that Li{0.9}Mo{6}O{17} is bipolar with large, partial Seebeck coefficients of opposite sign. A very large thermomagnetic figure of merit, ZT～0.5, is found at high field in the range T≈35-50 K.     

Studies of ⁶Li-NMR properties in different salt solutions in low magnetic fields

In this article we report the longitudinal relaxation times (T(1)) of various (6)Li salts ((6)LiI, (6)LiCl and (6)LiNO(3)) in D(2)O and H(2)O, measured in low magnetic fields (B(0)=3.5mT). This investigation serves the purpose of clarifying the relaxation behavior of different (6)Li solutions and different concentrations. The measurement were undertaken to establish a framework for future applications of hyperpolarized (6)Li in medical imaging, biological studies and investigations of lithium ion batteries. Time will pass during the transport of hyperpolarized lithium ions to the sample, which leads to a polarization loss. In order to store polarization as long as possible, it is necessary to examine which (6)Li salt solution has the longest relaxation time T(1). Longitudinal relaxation times of (6)Li salts in D(2)O and H(2)O were investigated as a function of concentration and the most extended T(1) was found for (6)LiI in D(2)O and H(2)O. In agreement with the theory the relaxation time T(1) of all (6)Li salts increase with decreasing concentration. In the case of (6)LiI in H(2)O an inverse behavior was observed. We assume that the prolonged T(1) times occur due to formation of (6)LiOH upon the solution of (6)LiI in H(2)O, which settles as a precipitate. By diluting the solution, the precipitate continuously dissolves and approaches T(1) of (6)LiOH (T(1)～28s), leading to a shorter T(1) relaxation time.     

Free energy and torque for superconductors with different anisotropies of H(c2) and lambda

The free energy is evaluated for a uniaxial superconductor with the anisotropy of the upper critical field, gamma(H)=H(c2,a)/H(c2,c), different from the anisotropy of the penetration depth gamma(lambda)=lambda(c)/lambda(a). With increasing difference between gamma(H) and gamma(lambda), the equilibrium orientation of the crystal relative to the applied field may shift from theta=pi/2 (theta is the angle between the field and the c axis) to lower angles and reach theta=0 for large enough gamma(H). These effects are expected to take place in MgB2.     

若干具有[（PO4）4Mo6^VO15]^12^-簇骼的化合物的光谱研究

Five novel organic-molybdenum phosphates with [(PO4)4Mo6(V)O15]12- cluster, Na x (H4TETA)3 x (H3O)5 x {Zn[(HPO4)2(PO4)2Mo6O15]2} (2), (H2en)7 x (H3O)4 x {Cu[(HPO4)2(PO4)2Mo6O15]2} x H2O (3), (H3DETA)2 x (H3O)3 x {Co0.5[(HPO4)2(PO4)2Mo6O15]} x H2O (4), [Co(H3TETA)]2{Co0.5[(HPO4)(PO4)3Mo6O15] x 3.5H2O (5) and (H3DETA) x (H3O)4 x {Co1.5 [(HPO4)2(PO4)2Mo6O15]} x 0.5H2O (6), have been synthesized. The relationship between their properties and structures was studied by using FTIR, NIR FT-Raman, UV-Vis DRS and fluorescence etc. In these compounds, every two [(PO4)4Mo6O15] clusters are coordinated by a metal atom to form a {M[(PO4)4Mo6O15]2} dimer. In compound 2, 3 and 4, {M[(PO4)4Mo6O15]2} dimers are hydrogen-bonded by the organic molecules and water molecules to form a three-dimensional expended framework, respectively. In compound 5 and 6, {Co[(PO4)4Mo6O15]2} dimers are coordinated by [Co(H3TETA)] groups and [CoO4] tetrahedra to form a network, respectively. These characteristic vibrational frequencies of the molybdenum phosphates are related to the structure of these compounds. Three characteristic bands in UV-Vis DRS spectra of these compounds have to be attributed to the absorptions of O(d) --> Mo, O(mu) --> Mo and O --> M charge transfer, respectively. These compounds exhibit strong fluorescence emission bands at about 410 nm when excited by 240 nm, which are caused by O(mu) --> Mo charge transfer.     

Scanning tunneling spectroscopy in the superconducting state and vortex cores of the beta-pyrochlore KOs2O6

We performed the first scanning tunneling spectroscopy measurements on the pyrochlore superconductor KOs2O6 (T(c)=9.6 K) in both zero magnetic field and the vortex state at several temperatures above 1.95 K. This material presents atomically flat surfaces, yielding spatially homogeneous spectra which reveal fully gapped superconductivity with a gap anisotropy of 30%. Measurements performed at fields of 2 and 6 T display a hexagonal Abrikosov flux line lattice. From the shape of the vortex cores, we extract a coherence length of 31-40 A, in agreement with the value derived from the upper critical field H(c2). We observe a reduction in size of the vortex cores (and hence the coherence length) with increasing field which is consistent with the unexpectedly high and unsaturated upper critical field reported.     

Lower critical field and superfluid density of highly underdoped YBa2Cu3O6+x single crystals

The lower critical field H(c1) for highly underdoped YBa2Cu3O(6+x) with T(c) between 8.9 and 22 K has been determined by measurements of magnetization M(H) curves with applied field parallel to the c axis. H(c1) is linear in temperatures below about 0.6T(c), and H(c1)(0) is proportional to T(1.64+/-0.04)(c), clearly violating the proportionality between rho(s)(0) and T(c). Moreover, the slope -dH(c1)/dT decreases steeply toward zero as T(c) approaches zero, indicating that the effective charge of the quasiparticles vanishes as the doping is decreased toward the insulating phase.     

Origin of the enhanced copper spin echo decay rate in the pseudogap regime of the multilayer high-T(c) cuprates

We report measurements of the anisotropy of the spin echo decay for the inner layer Cu site of the triple layer cuprate Hg(0.8)Re(0.2)Ba(2)Ca(2)Cu(3)O(8) (T(c)=126 K). The angular dependence of the second moment (T(-2)(2M) identical with ) deduced from the decay curves indicates that T(-2)(2M) for H0 parallel c is enhanced in the pseudogap regime below T(pg) approximately 170 K, as seen in bilayer systems. Comparison of T(-2)(2M) between H0 parallel c and H0 perpendicular c indicates that this enhancement is caused by electron spin correlations between the inner and the outer CuO2 layers. The results provide the answer to the long-standing controversy regarding the opposite T dependences of (T1T)(-1) and T(-2)(2G) (T(2G): Gaussian component) in the pseudogap regime of multilayer systems.     

含O3MoS3单元的配合物[Mox（CO）y（O,S—C6H4—1,2）3FezLm[^n—（x=1,2或3,y=0,3

用红外光谱研究标题配合物的结构,得到了很有意义的结果。     

First principles NMR calculations of phenylphosphinic acid C6H5HPO(OH): assignments, orientation of tensors by local field experiments and effect of molecular motion

The complete set of NMR parameters for (17)O enriched phenylphosphinic acid C(6)H(5)HP( *)O(*OH) is calculated from first principles by using the Gauge Including Projected Augmented Wave (GIPAW) approach [C.J. Pickard, F. Mauri, All-electron magnetic response with pseudopotentials: NMR chemical shifts, Phys. Rev. B 63 (2001) 245101/1-245101/13]. The analysis goes beyond the successful assignment of the spectra for all nuclei ((1)H, (13)C, (17)O, (31)P), as: (i) the (1)H CSA (chemical shift anisotropy) tensors (magnitude and orientation) have been interpreted in terms of H bonding and internuclear distances. (ii) CSA/dipolar local field correlation experiments have allowed the orientation of the direct P-H bond direction in the (31)P CSA tensor to be determined. Experimental and calculated data were compared. (iii) The overestimation of the calculated (31)P CSA has been explained by local molecular reorientation and confirmed by low temperature static (1)H-->(31)P CP experiments.     

Dimensional crossover in the purple bronze Li0.9Mo6O17

Thermal expansion of Li0.9Mo6O17 is a-axis dominated which reduces the separation of the conducting chains at low temperature enhancing the interchain coupling. This destabilizes the Luttinger-liquid fixed point leading to an electronic charge- (or spin-) density wave dominated by Coulomb repulsion, as predicted by theories for Luttinger liquids.     

Crystal structure and spin dynamics for the Li9V3P(8-δ)O(29-δ') insertion electrode system with a multiple-electron reaction

The crystal structure, the electron configurations of V ions and the spin dynamics for the Li(9)V(3)P(8-δ)O(29-δ') insertion electrode system that exhibits a multiple-electron reaction are explored through measurements of x-ray four-circle diffraction, magnetization and nuclear magnetic resonance. The structure for the stoichiometric composition with δ = δ' = 0 is refined precisely and the effective valences of all ions are determined. The electron configurations of V ions for the system annealed at various temperatures are considered in the framework of intermediate crystal field approach. For the system that often exhibits the charge-discharge performance better than the double-electron reaction, the spin dynamics mainly for the tetrahedral Li3 ions is understood on the basis of the relaxation mechanisms of quadrupole coupling and resonance shift anisotropy caused by the dipolar field of V ions. The correlation time of fluctuating fields is proportional to the temperature above 30 K, below which it follows the fractional Debye-Stokes-Einstein relation.     

Importance of in-plane anisotropy in the quasi-two-dimensional antiferromagnet BaNi2V2O8

The phase diagram of the quasi-two-dimensional antiferromagnet BaNi(2)V(2)O(8) is studied by specific heat, thermal expansion, magnetostriction, and magnetization for magnetic fields applied perpendicular to c. At micro(o)H* approximately 1.5 T, a crossover to a high-field state, where T(N)(H) increases linearly, arises from a competition of intrinsic and field-induced in-plane anisotropies. The pressure dependences of T(N) and H* are interpreted using the picture of a pressure-induced in-plane anisotropy. Even at zero field and ambient pressure, in-plane anisotropy cannot be neglected, which implies deviations from pure Berezinskii-Kosterlitz-Thouless behavior.     

Surface dynamics of Mo(1 1 0)–H and Mo(1 1 0)–Li

We compare the surface dynamics of the adsorbate systems Mo(1 1 0)–H and Mo(1 1 0)–Li. In both cases electron energy loss spectroscopy measurements revealed strong substrate surface phonon anomalies. Whereas the phonon anomaly of the hydrogen-covered surface was unequivocally assigned to be of the Kohn type, the anomalous behavior of the surface phonons of the lithium-covered surface remained obscure. In this paper we develop an experimental criterion based on the dispersion of adsorbate phonons, which allows to decide whether the observed substrate surface phonon anomaly is of the Kohn type or not. Employing this criterion we now definitely rule out that the anomaly on Mo(1 1 0)–Li is due to the Kohn effect.     

2,3-二羟基萘钼多酸有机衍生物的合成及1H NMR和IR谱学研究

本文对二种新合成的2，3－二羟基萘二钼和四钼多酸有机衍生物[n-Bu)4N]2[Mo2O5(OC10H6O)2](Ⅰ）和[n-Bu)4N]2[Mo4O10(OC10H6O)2(OCH3)2](Ⅱ)进行了红外光谱与核磁共振波谱研究，发现[Mo2O5]^2 中钼氧多桥键的红外振动频率较[Mo4O10(OCH3)2]^2 中钼氧多桥键的红外振动频率红移，而在配合物Ⅱ中2，3－二羟基中芳环的^1H化学位移较配合物Ⅰ中向低场移动。同时还发现含二钼配位中心[Mo2O5]^2 的[Mo2O5(OC10H6O)2]^2-与含四钼配位中心[Mo4O10(OCH3)2]^2 的[Mo4O10(OC10H6O)2(OCH3)2]^2-生成条件的差异仅仅只在反应体系的pH值的微小变化，说明钼多酸有机衍生物阴离子是对体系酸碱度极为敏感的物质。     

Structure and magnetic properties of the intermetallic La2Co17−xMox (x=0.5, 1, 1.5, 2) and La2Co16−yFeyMo (y=0, 1, 2, 3, 4, 6) compounds

The effect of Mo and Fe atoms on the crystal structure and magnetic properties of the intermetallic La₂Co_17−xMo_x (x=0.5, 1, 1.5, 2), and La₂Co_16−yFe_yMo (y=0, 1, 2, 3, 4, 6) compounds have been studied by X-ray diffractometry, magnetic measurements and Mössbauer spectroscopy. All samples belong to the rhombohedral Th₂Zn₁₇-type structure and their lattice parameters a and c increase both with Mo and Fe content. From the La–Co–Mo samples only the one with x=0.5 presents planar anisotropy, whereas from the La–Co–Fe–Mo samples only the y=1 has uniaxial anisotropy. The magnetization M_S and the Curie temperature T_C decrease upon Mo substitution, whereas the anisotropy field H_A does not change significantly. In the Fe-substituted compounds M_S increases, but the Curie temperature increases slightly for 0⩽y⩽4 but decreases in y=6. The low temperature M–T curve shows that the samples La₂Co_16.5Mo_0.5, and La₂Co₁₀Fe₆Mo present a spin reorientation transitions at 70 and 260 K, respectively. Mössbauer samples were obtained for all Fe-containing samples in the temperature range 20–300 K. Above 260 K a jump in the values of the hyperfine fields and quadrupole splitting parameters is observed which can be associated to the spin reorientation.     

Null orbital frustration at the pseudogap boundary in a layered cuprate superconductor

We assess the relative importance of orbital frustration at the pseudogap closing field H(pg). Using interlayer tunneling transport in pulsed magnetic fields nearly up to 60 T, we track the field-temperature (H-T) phase diagram for fields parallel ( parallel ab) and normal ( parallel c) to the layered structure of Bi(2)Sr(2)CaCu(2)O(8+y). In contrast to large orientational anisotropy of the superconducting state related to the orbital motion of Cooper pairs, we find anisotropy of H(pg) temperature independent and small, due solely to the g factor. The obtained Zeeman relation with the pseudogap temperature T small star, filled, g( parallel c)micro(B)H( parallel c)(pg)=g( parallel ab)micro(B)H( parallel ab)(pg) approximately k(B)T small star, filled, is fully consistent with the correlations only in the spin channel.     

A neutron powder diffraction study of the lithium insertion compound LiMoO2 from 4–440K

The structure of the lithium inserted rutile-based compound LiMoO₂ has been determined from neutron powder diffraction data by use of the Rietveld profile technique. The inserted Li is incorporated into the MoO₂ lattice in octahedral sites with an average Li0 distance of 2.12 Å. The Mo atoms also occupy octahedral sites with an average MoO distance of 2.12 ǎ, and form Mo-Mo pairs with a separation of 2.46 Å. LiMoO₂ can best be regarded as having a distorted NiAs-type structure rather than one of rutile-type. No changes in structure were observed in the temperature range 4–400K.     

Yields and transverse momenta of the 6Li fragments in the emulsion at 4.5 GeV/c per nucleon

We present the results of the study of interaction of the relativistic ⁶Li nucleus with the momentum 4.5 GeV/c per nucleon with the photoemulsion. Yields of the ¹H (³He) and ²H (⁴He) isotopes due to the fragmentation of ⁶Li are found to be almost equal. Cross sections for the charge exchange and pickup reactions are found to be σ_exch=9±2 mb. The distributions of the fragment transverse momenta projected onto the emulsion plane are used to obtain the nucleon Fermi momentum of ⁶Li, P_F, this value being equal to 129±8 MeV/c. The high momentum component in the transverse momentum distributions of ³He and ⁴He isotopes is observed. Received: 4 August 1997     

磁场对重电子金属材料CeCu6-xCdx电阻的影响

介绍了重电子金属CeCu6-x_6-xCdx_x（x=010，015，020，0 30，050）在18—300K温度范围内,在磁场(μ0₀H=0，5，10T)下电阻 随温度的变化规律 及低温（19 ，15K）下的磁电阻（μ0₀H=0—10T）.实验表明所有样品在 零场下的Tmax_max（对应于电阻极大值的温度）都低于18K.加磁场后，Tmax _max随磁场和掺杂量 关键词： 重电子系统 低温电阻 近藤散射 相干散射