In the last 30 days

• Open/close Raman scattering, central peak and phase transitions in AgNbO₃

  A Kania et al 1986 J. Phys. C: Solid State Phys. 19 9 Tag this article

  Article References Full text PDF (696 KB)

  Light-scattering investigations in the temperature range from 10 to 850K have been performed on single crystals of silver niobate AgNbO ₃. The results are compared with structural and dielectric measurements revealing a complex sequence of phases. The Raman results and especially the strong central peak, which occurs over a wide range of frequencies and temperatures, are analysed in connection with the various phase transformations. The specific contributions of the niobium and the silver ions are tentatively discussed.

• Open/close Persistent spectral hole burning of colour centres in diamond

  R T Harley et al 1984 J. Phys. C: Solid State Phys. 17 L233 Tag this article

  Article References Full text PDF (259 KB)

  Four zero-phonon lines of defect centres in diamond (GR1 (741 nm), N-V (637 nm), H4 (496 nm) and N3 (415 nm)) have been shown to exhibit persistent spectral hole burning. The phenomenon appears to be a rather general one in diamond and should prove very powerful for elucidation of the nature of defect centres. As an example, preliminary results for the N-V centre suggest a previously undetected splitting of the excited state.

• Open/close Ordering, metastability and phase transitions in two-dimensional systems

  J M Kosterlitz and D J Thouless 1973 J. Phys. C: Solid State Phys. 6 1181 Tag this article

  Article References Full text PDF (1.23 MB)

  A new definition of order called topological order is proposed for two-dimensional systems in which no long-range order of the conventional type exists. The possibility of a phase transition characterized by a change in the response of the system to an external perturbation is discussed in the context of a mean field type of approximation. The critical behaviour found in this model displays very weak singularities. The application of these ideas to the xy model of magnetism, the solid-liquid transition, and the neutral superfluid are discussed. This type of phase transition cannot occur in a superconductor nor in a Heisenberg ferromagnet.

• Open/close Oscillatory effects and the magnetic susceptibility of carriers in inversion layers

  Yu A Bychkov and E I Rashba 1984 J. Phys. C: Solid State Phys. 17 6039 Tag this article

  Article References Full text PDF (415 KB)

  Oscillatory effects in a strong magnetic field B and magnetic susceptibility are investigated, as applied to 2D systems, in which the twofold spin degeneracy is lifted by the spin-orbit-interaction Hamiltonian H _SO= alpha ( sigma *k). nu . The term H _SO is shown to change greatly the usual patterns of B ^-1-periodic oscillations; some oscillations are strongly suppressed due to the diminishing of the gaps between adjacent levels, and new oscillations appear due to intersections of levels.

• Open/close Coulomb gap and low temperature conductivity of disordered systems

  A L Efros and B I Shklovskii 1975 J. Phys. C: Solid State Phys. 8 L49 Tag this article

  Article References Full text PDF (232 KB)

  The Coulomb interaction between localized electrons is shown to create a 'soft' gap in the density of states near the Fermi level. The new temperature dependence of the hopping DC conductivity is the most important manifestation of the gap. The form of the density of states within the gap is discussed.

• Open/close One-dimensional transport and the quantisation of the ballistic resistance

  D A Wharam et al 1988 J. Phys. C: Solid State Phys. 21 L209 Tag this article

  Article References Full text PDF (341 KB)

  The authors present experimental results, and a supporting theory, showing that a one-dimensional system in which transport is ballistic possesses a quantised resistance, h/2ie ², where i is the number of occupied 1D sub-bands and the spin degeneracy is two. A short narrow channel is defined in the 2DEG of a GaAs-AlGaAs heterojunction and as the width of the system is changed, the sub-bands pass through the Fermi energy and the resistance jumps between quantised values. The value of the quantised resistance is derived and the accuracy of the quantisation is discussed. The effect can be strong at temperatures approximately 0.1 K, with up to 17 sub-bands being observed. The action of a transverse magnetic field is to depopulate the sub-bands and form hybrid levels; a parallel field lifts the spin degeneracy and brings about a further quantisation of resistance at values h/2(i+ ¹/ ₂)e ².

• Open/close Spiral magnetic ordering in bismuth ferrite

  I Sosnowska et al 1982 J. Phys. C: Solid State Phys. 15 4835 Tag this article

  Article References Full text PDF (661 KB)

  New information on the magnetic ordering of the iron ions in bismuth ferrite BiFeO ₃ was obtained by a study with a high-resolution time-of-flight neutron diffractometer. The observed splitting of magnetic diffraction maxima could be interpreted in terms of a magnetic cycloidal spiral with a long period of 620+or-20 AA, which is unusual for perovskites.

• Open/close Momentum-space formalism for the total energy of solids

  J Ihm et al 1979 J. Phys. C: Solid State Phys. 12 4409 Tag this article

  Article References Full text PDF (827 KB)

  A momentum-space formalism for calculating the total energy of solids is derived. This formalism is designed particularly for application with the self-consistent pseudopotential method. In the present formalism, the total energy is obtained through band-structure calculations without involving additional integrations. The Hellman-Feynman theorem is derived, as is a modified virial relation for the pseudopotential Hamiltonian which provides an alternative way of calculating forces and total energies.

• Open/close Direct calculation of the tunneling current

  C Caroli et al 1971 J. Phys. C: Solid State Phys. 4 916 Tag this article

  Article References Full text PDF (825 KB)

  A simple model Hamiltonian is proposed for a metal-insulator- metal tunneling junction, which permits the direct calculation of the tunneling current without introducing any effective Hamiltonian. The model rests on the use of localized functions; this procedure avoids the difficult matching problem at the boundary between the barrier and the electrodes. Moreover the use of Kjeldysh's perturbation theory for nonequilibrium system allows an explicit calculation of the current to all orders in the applied bias. It is found that the transfer coefficient appearing in the expression for the current is energy dependent. This model can be systematically extended to include many body effects.

• Open/close 'Luttinger liquid theory' of one-dimensional quantum fluids. I. Properties of the Luttinger model and their extension to the general 1D interacting spinless Fermi gas

  F D M Haldane 1981 J. Phys. C: Solid State Phys. 14 2585 Tag this article

  Article References Full text PDF (1.55 MB)

  The explicitly soluble Luttinger model is used as a basis for the description of the general interacting Fermi gas in one dimension, which will be called 'Luttinger liquid theory', by analogy with Fermi liquid theory. The excitation spectrum of the Luttinger model is described by density-wave, charge and current excitations; its spectral properties determine a characteristic parameter that controls the correlation function exponents. These relations are shown to survive in non-soluble generalisations of the model with a non-linear fermion dispersion. It is proposed that this low-energy structure is universal to a wide class of 1D systems with conducting or fluid properties, including spin chains.