Electronic properties of emergent topological defects in chiral pp-wave superconductivity

Chiral $p$-wave superconductors in applied magnetic field can exhibit more complex topological defects than just conventional superconducting vortices, due to the two-component order parameter (OP) and the broken time-reversal symmetry. We investigate the electronic properties of those exotic states, some of which contain clusters of one-component vortices in chiral components of the OP and/or exhibit skyrmionic character in the \textit{relative} OP space, all obtained as a self-consistent solution of the microscopic Bogoliubov-de Gennes equations. We reveal the link between the local density of states (LDOS) of the novel topological states and the behavior of the chiral domain wall between the OP components, enabling direct identification of those states in scanning tunneling microscopy. For example, a skyrmion always contains a closed chiral domain wall, which is found to be mapped exactly by zero-bias peaks in LDOS. Moreover, the LDOS exhibits electron-hole asymmetry, which is different from the LDOS of conventional vortex states with the same vorticity. Finally, we present the magnetic field and temperature dependence of the properties of a skyrmion, indicating that this topological defect can be surprisingly large in size, and can be pinned by an artificially indented non-superconducting closed path in the sample. These features are expected to facilitate the experimental observation of skyrmionic states, thereby enabling experimental verification of chirality in emerging superconducting materials

Phase diagram of a polydisperse soft-spheres model for liquids and colloids

The phase diagram of soft spheres with size dispersion has been studied by means of an optimized Monte Carlo algorithm which allows to equilibrate below the kinetic glass transition for all sizes distribution. The system ubiquitously undergoes a first order freezing transition. While for small size dispersion the frozen phase has a crystalline structure, large density inhomogeneities appear in the highly disperse systems. Studying the interplay between the equilibrium phase diagram and the kinetic glass transition, we argue that the experimentally found terminal polydispersity of colloids is a purely kinetic phenomenon.Comment: Version to be published in Physical Review Letter

Separation and fractionation of order and disorder in highly polydisperse systems

Microcanonical Monte Carlo simulations of a polydisperse soft-spheres model for liquids and colloids have been performed for very large polydispersity, in the region where a phase-separation is known to occur when the system (or part of it) solidifies. By studying samples of different sizes, from N=256 to N=864, we focus on the nature of the two distinct coexisting phases. Measurements of crystalline order in particles of different size reveal that the solid phase segregates between a crystalline solid with cubic symmetry and a disordered phase. This phenomenon is termed fractionation.Comment: 8 pages, 5 figure

Second Order Darboux Displacements

The potentials for a one dimensional Schroedinger equation that are displaced along the x axis under second order Darboux transformations, called 2-SUSY invariant, are characterized in terms of a differential-difference equation. The solutions of the Schroedinger equation with such potentials are given analytically for any value of the energy. The method is illustrated by a two-soliton potential. It is proven that a particular case of the periodic Lame-Ince potential is 2-SUSY invariant. Both Bloch solutions of the corresponding Schroedinger equation equation are found for any value of the energy. A simple analytic expression for a family of two-gap potentials is derived

Long-range spin-qubit interaction mediated by microcavity polaritons

We study the optically-induced coupling between spins mediated by polaritons in a planar micro-cavity. In the strong coupling regime, the vacuum Rabi splitting introduces anisotropies in the spin coupling. Moreover, due to their photon-like mass, polaritons provide an extremely long spin coupling range. This suggests the realization of two-qubit all-optical quantum operations within tens of picoseconds with spins localized as far as hundreds of nanometers apart.Comment: 5 pages, 3 figure

Sphere rolling on the surface of a cone

We analyse the motion of a sphere that rolls without slipping on a conical surface having its axis in the direction of the constant gravitational field of the Earth. This nonholonomic system admits a solution in terms of quadratures. We exhibit that the only circular of the system orbit is stable and furthermore show that all its solutions can be found using an analogy with central force problems. We also discuss the case of motion with no gravitational field, that is, of motion on a freely falling cone.Comment: 12 pages, 2 figures, to be published in Eur J Phy

Hydrogen atom in crossed external fields reexemined by the moment method

Recurrence relations of perturbation theory for hydrogen ground state are obtained. With their aid polarizabilities in constant perpendicular electric and magnetic fields are computed up to 80th order. The high orders asymptotic is compared with its quasiclassical estimate. For the case of arbitrary mutual orientation of external fields a general sixth order formula is given.Comment: 11 pages, LaTeX, 2 figures (eps

Equilibrium fluid-solid coexistence of hard spheres

We present a tethered Monte Carlo simulation of the crystallization of hard spheres. Our method boosts the traditional umbrella sampling to the point of making practical the study of constrained Gibb's free energies depending on several crystalline order-parameters. We obtain high-accuracy estimates of the fluid-crystal coexistence pressure for up to 2916 particles (enough to accommodate fluid-solid interfaces). We are able to extrapolate to infinite volume the coexistence pressure (p_{co}=11.5727(10) k_B T/\sigma^3) and the interfacial free energy (\gamma_{100}=0.636(11) k_B T/\sigma^2).Comment: 6 pages, 4 pdf figures. Version to be published in PRL. Appendices contain Supplemental Materia