Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

The realization of superfluidity in a dilute gas of fermionic atoms, analogous to superconductivity in metals, represents a long-standing goal of ultracold gas research. In such a fermionic superfluid, it should be possible to adjust the interaction strength and tune the system continuously between two limits: a Bardeen–Cooper–Schrieffer (BCS)-type superfluid (involving correlated atom pairs in momentum space) and a Bose–Einstein condensate (BEC), in which spatially local pairs of atoms are bound together. This crossover between BCS-type superfluidity and the BEC limit has long been of theoretical interest, motivated in part by the discovery of high-temperature superconductors. In atomic Fermi gas experiments superfluidity has not yet been demonstrated; however, long-lived molecules consisting of locally paired fermions have been reversibly created. Here we report the direct observation of a molecular Bose–Einstein condensate created solely by adjusting the interaction strength in an ultracold Fermi gas of atoms. This state of matter represents one extreme of the predicted BCS–BEC continuum.

Emergence of a molecular Bose-Einstein condensate from a Fermi gas

We have developed an efficient simulation tool 'GOLLUM' for the computation of electrical, spin and thermal transport characteristics of complex nanostructures. The new multi-scale, multi-terminal tool addresses a number of new challenges and functionalities that have emerged in nanoscale-scale transport over the past few years. To illustrate the flexibility and functionality of GOLLUM, we present a range of demonstrator calculations encompassing charge, spin and thermal transport, corrections to density functional theory such as local density approximation + U ( LDA+ U) and spectral adjustments, transport in the presence of non-collinear magnetism, the quantum Hall effect, Kondo and Coulomb blockade effects, finite-voltage transport, multi-terminal transport, quantum pumps, superconducting nanostructures, environmental effects, and pulling curves and conductance histograms for mechanically-controlled break-junction experiments.

/pdf/gollum-a-next-generation-simulation-tool-for-electron-4f0hj5yoex.pdf

GOLLUM:a next-generation simulation tool for electron, thermal and spin transport

We have developed an efficient simulation tool 'GOLLUM' for the computation of electrical, spin and thermal transport characteristics of complex nanostructures. The new multi-scale, multi-terminal tool addresses a number of new challenges and functionalities that have emerged in nanoscale-scale transport over the past few years. To illustrate the flexibility and functionality of GOLLUM, we present a range of demonstrator calculations encompassing charge, spin and thermal transport, corrections to density functional theory such as LDA+U and spectral adjustments, transport in the presence of non-collinear magnetism, the quantum-Hall effect, Kondo and Coulomb blockade effects, finite-voltage transport, multi-terminal transport, quantum pumps, superconducting nanostructures, environmental effects and pulling curves and conductance histograms for mechanically-controlled-break-junction experiments.

GOLLUM: a next-generation simulation tool for electron, thermal and spin transport

We present an analytic prescription for computing the edge dispersion $E(k)$ of a tight-binding Dirac Hamiltonian terminated at an abrupt crystalline edge. Specifically, we consider translationally invariant Dirac Hamiltonians with nearest-layer interaction. We present and prove a geometric formula that relates the existence of surface states as well as their energy dispersion to properties of the bulk Hamiltonian. We further prove the bulk-boundary correspondence between the Chern number and the chiral edge modes for quantum Hall systems within the class of Hamiltonians studied in the paper. Our results can be extended to the case of continuum theories that are quadratic in the momentum as well as other symmetry classes.

/pdf/edge-states-and-the-bulk-boundary-correspondence-in-dirac-3pmzx6tzci.pdf

Edge states and the bulk-boundary correspondence in Dirac Hamiltonians

Inverse magnetic catalysis in Nambu–Jona-Lasinio model beyond mean field

Pions in an external magnetic field are investigated in the frame of a Pauli-Villars regularized Nambu--Jona-Lasinio model The meson propagators in terms of quark bubbles in Ritus and Schwinger schemes are analytically derived, and pion masses are numerically calculated in the Ritus scheme For neutral and charged pions at finite temperature, there exist mass jumps at the Mott transition points due to the discrete energy levels of the two constituent quarks in the magnetic field

Pions in magnetic field at finite temperature

The spectrum and wave function of helical edge modes in ${Z}_{2}$ topological insulator are derived on a square lattice using Bernevig-Hughes-Zhang (BHZ) model. The BHZ model is characterized by a ``mass'' term $M(\mathbit{k})=\ensuremath{\Delta}\ensuremath{-}B{\mathbit{k}}^{2}$. A topological insulator realizes when the parameters $\ensuremath{\Delta}$ and $B$ fall on the regime, either $0l\ensuremath{\Delta}/Bl4$ or $4l\ensuremath{\Delta}/Bl8$. At $\ensuremath{\Delta}/B=4$, which separates the cases of positive and negative (quantized) spin Hall conductivities, the edge modes show a corresponding change that depends on the edge geometry. In the (1,0) edge, the spectrum of edge mode remains the same against change in $\ensuremath{\Delta}/B$, although the main location of the mode moves from the zone center for $\ensuremath{\Delta}/Bl4$, to the zone boundary for $\ensuremath{\Delta}/Bg4$ of the one-dimensional (1D) Brillouin zone. In the (1,1)-edge geometry, the group velocity at the zone center changes sign at $\ensuremath{\Delta}/B=4$ where the spectrum becomes independent of the momentum, i.e., flat, over the whole 1D Brillouin zone. Furthermore, for $\ensuremath{\Delta}/Bl1.354$, the edge mode starting from the zone center vanishes in an intermediate region of the 1D Brillouin zone, but reenters near the zone boundary, where the energy of the edge mode is marginally below the lowest bulk excitations. On the other hand, the behavior of reentrant mode in real space is indistinguishable from an ordinary edge mode.

/pdf/zigzag-edge-modes-in-a-z2-topological-insulator-reentrance-1fgvotyo2z.pdf

Zigzag edge modes in a Z2 topological insulator : Reentrance and completely flat spectrum

The meson static properties are investigated in a Pauli-Villars regularized Nambu--Jona-Lasinio model in a strong magnetic field. The quark dimension reduction leads to a sudden jump of the mass of the Goldstone mode at the Mott transition temperature. A consequence of such a jump may be some interesting phenomena in relativistic heavy ion collisions, where the strong magnetic field can be created. For instance, when the formed fireball cools down, there might be a sudden enhancement of neutral pions at the Mott transition temperature.

Effect of discrete quark momenta on the Goldstone mode in a magnetic field

Spectrum and wave function of gapless edge modes are derived analytically for a tight-binding model of topological insulators on square lattice. Particular attention is paid to dependence on edge geometries such as the straight (1,0) and zigzag (1,1) edges in the thermodynamic limit. The key technique is to identify operators that combine to annihilate the edge state in the effective one-dimensional (1D) model with momentum along the edge. In the (1,0) edge, the edge mode is present either around the center of 1D Brillouin zone or its boundary, depending on location of the bulk excitation gap. In the (1,1) edge, the edge mode is always present both at the center and near the boundary. Depending on system parameters, however, the mode is absent in the middle of the Brillouin zone. In this case the binding energy of the edge mode near the boundary is extremely small; about 10 -3 of the overall energy scale. Origin of this minute energy scale is discussed.

Shijun Mao

Papers

Inverse magnetic catalysis in Nambu–Jona-Lasinio model beyond mean field

Pions in magnetic field at finite temperature

Zigzag edge modes in a Z2 topological insulator : Reentrance and completely flat spectrum

Effect of discrete quark momenta on the Goldstone mode in a magnetic field

Analytic theory of edge modes in topological insulators