There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

This article reviews the basic theoretical aspects of graphene, a one-atom-thick allotrope of carbon, with unusual two-dimensional Dirac-like electronic excitations. The Dirac electrons can be controlled by application of external electric and magnetic fields, or by altering sample geometry and/or topology. The Dirac electrons behave in unusual ways in tunneling, confinement, and the integer quantum Hall effect. The electronic properties of graphene stacks are discussed and vary with stacking order and number of layers. Edge (surface) states in graphene depend on the edge termination (zigzag or armchair) and affect the physical properties of nanoribbons. Different types of disorder modify the Dirac equation leading to unusual spectroscopic and transport properties. The effects of electron-electron and electron-phonon interactions in single layer and multilayer graphene are also presented.

/pdf/the-electronic-properties-of-graphene-2siyzsnf5w.pdf

The electronic properties of graphene

J. Appl. Cryst.の発刊に際して

We review the dynamical mean-field theory of strongly correlated electron systems which is based on a mapping of lattice models onto quantum impurity models subject to a self-consistency condition. This mapping is exact for models of correlated electrons in the limit of large lattice coordination (or infinite spatial dimensions). It extends the standard mean-field construction from classical statistical mechanics to quantum problems. We discuss the physical ideas underlying this theory and its mathematical derivation. Various analytic and numerical techniques that have been developed recently in order to analyze and solve the dynamical mean-field equations are reviewed and compared to each other. The method can be used for the determination of phase diagrams (by comparing the stability of various types of long-range order), and the calculation of thermodynamic properties, one-particle Green's functions, and response functions. We review in detail the recent progress in understanding the Hubbard model and the Mott metal-insulator transition within this approach, including some comparison to experiments on three-dimensional transition-metal oxides. We present an overview of the rapidly developing field of applications of this method to other systems. The present limitations of the approach, and possible extensions of the formalism are finally discussed. Computer programs for the numerical implementation of this method are also provided with this article.

Dynamical mean-field theory of strongly correlated fermion systems and the limit of infinite dimensions

Point-contact Andreev reflection spectroscopy was performed on single crystals of the heavy-fermion superconductor PrOs$_{4}$Sb$_{12}$, down to 90mK and up to 3Tesla. The conductance spectra showed multiple structures, including zero-bias peaks and spectral dips, which are interpreted as signatures of multiple pairing gaps, one clearly having nodes. Samples with 2% Ru replacing Os were also measured, showing pronounced spectral humps consistent with the emergence of a non-nodal gap. Detailed analysis of the spectral evolution revealed a magnetic field-\emph{vs.}-temperature phase diagram for PrOs$_{4}$Sb$_{12}$ characterized by two distinct superconducting order parameters.

Andreev reflection spectroscopy on the heavy-fermion superconductor PrOs$_{4}$Sb$_{12}$: Microscopic evidence for multiple superconducting order parameters

http://absimage.aps.org/image/MAR08/MWS_MAR08-2007-003705.pdf

Non-Fermi liquid behavior in the filled skutterudite compound CeRu$_{4}$As$_{12}$

The hydrostatic pressure dependence of the superconducting critical temperature, T c , was measured in highly crystalline oriented REBa 2 Cu 3 O 7−δ (RE=Yb, Dy, Y, Gd) thin films grown on different substrates. The anisotropic strain field induced by the substrate and the different crystalline orientations of the films allows the three strain derivatives of the critical temperature to be estimated. A large anisotropy is found in the ab plane with T c increasing on compression parallel to the CuO chains and decreasing on compression perpendicular to them. The results on c textured films indicate a non linear relation between T c and the microscopic parameter which determines its pressure dependence.

Anisotropic pressure dependence of the critical temperature of REBa2Cu3O7−δ

Charge transport measurements under magnetic field and pressure on Ce1-xYbxCoIn5 single crystalline alloys revealed that: (i) relatively small Yb substitution suppresses the field induced quantum critical point, with a complete suppression for Yb doping x > 0.07; (ii) the superconducting transition temperature (Tc) and Kondo lattice coherence temperature (Tcoh) decrease with x, yet they remain finite over the wide range of Yb concentrations; (iii) both Tc and Tcoh increase with pressure; (iv) there are two contributions to resistivity, which show different temperature and pressure dependences, implying that both heavy and light quasiparticles contribute to inelastic scattering. We also analyzed the pressure dependence of both Tcoh and Tc within the composite pairing theory. In the purely static limit, we find that the composite pairing mechanism necessarily causes opposite behaviors of Tcoh and Tc with pressure: if Tcoh grows with pressure, Tc must decrease with pressure and vice versa.

/pdf/quantum-criticality-and-superconducting-pairing-in-ce-1-x-yb-4oge91yp4j.pdf

Quantum criticality and superconducting pairing in Ce 1-x Yb x CoIn 5 alloys

We report on the growth of thin films of the electron-doped superconductor Sm 2− x Ce x CuO 4− y (SCCO) by pulsed laser deposition (PLD) Electrical resistivity ρ ( H ,  T ) measurements on the thin films were made at temperatures T between 20 mK and 300 K in magnetic fields H up to 18 T The superconducting transition temperature is as high as T c  = 178 K, with a transition width Δ T c  = 093 K, for an optimally doped film The ρ ( H ,  T ) measurements on this thin film are compared to similar measurements made on single crystals A vortex-glass scaling analysis was applied to the ρ ( H ,  T ) data, yielding values of the vortex-glass melting temperature T g and critical exponent ν ( z  − 1) In addition, ρ ( H ,  T ) data are presented for an underdoped sample with x  = 0125, also grown via PLD

M. B. Maple

Papers

Andreev reflection spectroscopy on the heavy-fermion superconductor PrOs$_{4}$Sb$_{12}$: Microscopic evidence for multiple superconducting order parameters

Non-Fermi liquid behavior in the filled skutterudite compound CeRu$_{4}$As$_{12}$

Anisotropic pressure dependence of the critical temperature of REBa2Cu3O7−δ

Quantum criticality and superconducting pairing in Ce 1-x Yb x CoIn 5 alloys

Growth via pulsed laser deposition and characterization of thin films of the electron-doped superconductor Sm2−xCexCuO4−y