Pressure effects on the heavy-fermion antiferromagnet CeAuSb2

The f-electron compound CeAuSb2, which crystallizes in the ZrCuSi2-type tetragonal structure, orders antiferromagnetically between 5 and 6.8 K, where the antiferromagnetic transition temperature T_N depends on the occupancy of the Au site. Here we report the electrical resistivity and heat capacity of a high-quality crystal CeAuSb2 with T_N of 6.8 K, the highest for this compound. The magnetic transition temperature is initially suppressed with pressure, but is intercepted by a new magnetic state above 2.1 GPa. The new phase shows a dome shape with pressure and coexists with another phase at pressures higher than 4.7 GPa. The electrical resistivity shows a T^2 Fermi liquids behavior in the complex magnetic state, and the residual resistivity and the T^2 resistivity coefficient increases with pressure, suggesting the possibility of a magnetic quantum critical point at a higher pressure.Comment: 5 pages, 5 firure

Exotic Smooth Structures on Small 4-Manifolds

Let M be either CP^2#3CP^2bar or 3CP^2#5CP^2bar. We construct the first example of a simply-connected symplectic 4-manifold that is homeomorphic but not diffeomorphic to M.Comment: 11 page

The change of Fermi surface topology in Bi2Sr2CaCu2O8 with doping

We report the observation of a change in Fermi surface topology of Bi2Sr2CaCu2O8 with doping. By collecting high statistics ARPES data from moderately and highly overdoped samples and dividing the data by the Fermi function, we answer a long standing question about the Fermi surface shape of Bi2Sr2CaCu2O8 close to the (pi,0) point. For moderately overdoped samples (Tc=80K) we find that both the bonding and antibonding sheets of the Fermi surface are hole-like. However for a doping level corresponding to Tc=55K we find that the antibonding sheet becomes electron-like. This change does not directly affect the critical temperature and therefore the superconductivity. However, since similar observations of the change of the topology of the Fermi surface were observed in LSCO and Bi2Sr2Cu2O6, it appears to be a generic feature of hole-doped superconductors. Because of bilayer splitting, though, this doping value is considerably lower than that for the single layer materials, which again argues that it is unrelated to Tc

Intrinsic Pinning in the High Field C-Phase of UPt_3

We report on the a.c. magnetic response of superconducting UPt_3 in a d.c. magnetic field. At low fields (H < H^*), the in-phase susceptibility shows a sharp drop at $T_c$ followed by a gradual decrease with decreasing temperature, while the out-of-phase component shows a large peak at T_c followed by an unusual broad peak. As the B-C phase line is crossed (H>H^*), however, both the in-phase and out-of-phase susceptibilities resemble the zero-field Meissner curves. We interpret these results in terms of a vortex pinning force which, while comparatively small in the A/B-phases, becomes large enough to effectively prevent vortex motion in the C-phase.Comment: Modified discussion, slight changes to figures, accepted in PRB Rapid Communications. RevTex file, 5 figure

A predictive standard model for heavy electron systems

We propose a predictive standard model for heavy electron systems based on a detailed phenomenological two-fluid description of existing experimental data. It leads to a new phase diagram that replaces the Doniach picture, describes the emergent anomalous scaling behavior of the heavy electron (Kondo) liquid measured below the lattice coherence temperature, T*, seen by many different experimental probes, that marks the onset of collective hybridization, and enables one to obtain important information on quantum criticality and the superconducting/antiferromagnetic states at low temperatures. Because T* is ~J^2\rho/2, the nearest neighbor RKKY interaction, a knowledge of the single-ion Kondo coupling, J, to the background conduction electron density of states, \rho, makes it possible to predict Kondo liquid behavior, and to estimate its maximum superconducting transition temperature in both existing and newly discovered heavy electron families.Comment: 4 pages, 2 figures, submitted to J. Phys.: Conf. Ser. for SCES 201

Derivation of continuum stochastic equations for discrete growth models

We present a formalism to derive the stochastic differential equations (SDEs) for several solid-on-solid growth models. Our formalism begins with a mapping of the microscopic dynamics of growth models onto the particle systems with reactions and diffusion. We then write the master equations for these corresponding particle systems and find the SDEs for the particle densities. Finally, by connecting the particle densities with the growth heights, we derive the SDEs for the height variables. Applying this formalism to discrete growth models, we find the Edwards-Wilkinson equation for the symmetric body-centered solid-on-solid (BCSOS) model, the Kardar-Parisi-Zhang equation for the asymmetric BCSOS model and the generalized restricted solid-on-solid (RSOS) model, and the Villain--Lai--Das Sarma equation for the conserved RSOS model. In addition to the consistent forms of equations for growth models, we also obtain the coefficients associated with the SDEs.Comment: 5 pages, no figur

Monoclinic phase in the relaxor-based piezo-/ ferroelectric Pb(Mg1/3_{1/3}Nb2/3)O3_{2/3})O_3-PbTiO3_3 system

A ferroelectric monoclinic phase of space group $Cm$ ($M_A$ type) has been discovered in 0.65Pb(Mg$_{1/3}$Nb$_{2/3})O_3$-0.35PbTiO$_3$ by means of high resolution synchrotron X-ray diffraction. It appears at room temperature in a single crystal previously poled under an electric field of 43 kV/cm applied along the pseudocubic [001] direction, in the region of the phase diagram around the morphotropic phase boundary between the rhombohedral (R3m) and the tetragonal (P4mm) phases. The monoclinic phase has lattice parameters a = 5.692 A, b = 5.679 A, c = 4.050 A and $\beta$ = $90.15^{\circ}$, with the b$_m$-axis oriented along the pseudo-cubic [110] direction . It is similar to the monoclinic phase observed in PbZr$_{1-x}$Ti$_x$O$_3$, but different from that recently found in Pb(Zn$_{1/3}$Nb$_{2/3})O_3$-PbTiO$_3$, which is of space group $Pm$ ($M_C$ type).Comment: Revised version after referees' comments. PDF file. 6 pages, 4 figures embedde

Quenched Fe Moment in the Collapsed Tetragonal Phase of Ca1−x_{1-x}Prx_{x}Fe2_2As2_2

We report $^{75}$As NMR studies on single crystals of rare-earth doped iron pnictides superconductor Ca$_{1-x}$Pr$_{x}$Fe$_{2}$As$_{2}$ ($x$=0.075 and 0.15). The $^{75}$As spectra show a chemical pressure effect with doping and a first order structure transition to the collapsed tetragonal phase upon cooling. A sharp drop of the Knight shift is seen below the structural transition, whereas $1/T_1$ is strongly enhanced at low-temperatures. These evidences indicate quenching of Fe local magnetism and short-range ordering of Pr$^{3+}$ moment in the collapsed tetragonal phase. The quenched Fe moment through structure collapse suggests a strong interplay of structure and magnetism, which is important for understanding the nature of the collapsed tetragonal phase.Comment: 5 pages, 5 figure

Lensing in an interior Kottler solution

We derive the interior Kottler solution of the incompressible fluid and show that the bending of light in this solution does depend on the cosmological constant.Comment: The inner Kottler solution derived and used in this paper is not new. Corresponding references to Stuchlik (2000) and Boehmer (2003) are added. Also added: a numerical example and a figure. This is the version accepted by Gen. Rel. Grav. However it includes a short passage that an anonymous referee had me suppress

Remarks on the Scalar Graviton Decoupling and Consistency of Horava Gravity

Recently Horava proposed a renormalizable gravity theory with higher derivatives by abandoning the Lorenz invariance in UV. But there have been confusions regarding the extra scalar graviton mode and the consistency of the Horava model. I reconsider these problems and show that, in the Minkowski vacuum background, the scalar graviton mode can be consistency decoupled from the usual tensor graviton modes by imposing the (local) Hamiltonian as well as the momentum constraints.Comment: Some clarifications regarding the projectable case added, Typos corrected, Comments (Footnote No.9, Note Added) added, References updated, Accepted in CQ