On the Problem of Spontaneous Isotopic Symmetry Breaking in Nambu–Jona-Lasinio Models

Physics of Particles and Nuclei Letters - The problem of spontaneous isotopic symmetry breaking in Nambu–Jona-Lasinio quark models is considered. It is shown that, in models with light...     

Interactions between particles with an undulated contact line at a fluid interface: capillary multipoles of arbitrary order

A colloidal particle adsorbed at a fluid interface could have an undulated, or irregular contact line in the presence of surface roughness and/or chemical inhomogeneity. The contact-line undulations produce distortions in the surrounding liquid interface, whose overlap engenders capillary interaction between the particles. The convex and concave local deviations of the meniscus shape from planarity can be formally treated as positive and negative "capillary charges," which form "capillary multipoles." Here, we derive theoretical expressions for the interaction between two capillary multipoles of arbitrary order. Depending on the angle of mutual orientation, the interaction energy could exhibit a minimum, or it could represent a monotonic attraction. For undulation amplitudes larger than 5 nm, the interaction energy is typically much greater than the thermal energy kT. As a consequence, a monolayer from capillary multipoles exhibits considerable shear elasticity, and such monolayer is expected to behave as a two-dimensional elastic solid. These theoretical results could be helpful for the understanding of phenomena related to aggregation and ordering of particles adsorbed at a fluid interface, and for the interpretation of rheological properties of particulate monolayers. Related research fields are the particle-stabilized (Pickering) emulsions and the two-dimensional self-assembly of microscopic particles.     

New mechanism of chaos in triangular billiards

A new mechanism of weak chaos in triangular billiards has been proposed owing to the effect of cutting of beams of rays. A similar mechanism is also implemented in other polygonal billiards. Cutting of beams results in the separation of initially close rays at a finite angle by jumps in the process of reflections of beams at the vertices of a billiard. The opposite effect of joining of beams of rays occurs in any triangular billiard along with cutting. It has been shown that the cutting of beams has an absolute character and is independent of the form of a triangular billiard or the parameters of a beam. On the contrary, joining has a relative character and depends on the commensurability of the angles of the triangle with π. Joining always suppresses cutting in triangular billiards whose angles are commensurable with π. For this reason, their dynamics cannot be chaotic. In triangular billiards whose angles are rationally incommensurable with π, cutting always dominates, leading to weak chaos. The revealed properties are confirmed by numerical experiments on the phase portraits of typical triangular billiards.     

Emergence and visualization of an interface state during contact formation with a single molecule

Contact formation dynamics and electronic perturbations arising from the interaction of a metallic probe and a single molecule (1,3 cyclohexadiene) bound on the Si (100) surface are examined using a series of plane wave, density functional theory calculations. The approach of the probe induces a relaxation of the molecule that ultimately leads to the formation of an interface state due to a specific interaction between the probe apex atom and the C=C bond of the molecule. The calculated interface state is located 0.2 eV above the Fermi energy, in agreement with low temperature scanning tunneling spectroscopy local density of states data (0.35 eV), and is responsible for the contrast observed in low bias empty-state STM images.     

Double-Lattice Magnetoplasmonic Structures Based on BIG and Perforated Gold Films

Physics of the Solid State - A method of manufacturing double-lattice magnetoplasmonic crystals with the structure (Au/BIG)2, in which the plasmon gold lattices are displaced relative to each other...     

Sodium adsorption on a Ge(100)-(2 × 1) surface

The adsorption of Na on a Ge(100)-(2 × 1) surface has been studied by means of AES, LEED, EELS, TPD and work-function measurements. In the submonolayer coverage region the coverage dependencies of the desorption activation energy E(Θ) and desorption frequency v(Θ) have been determined using the threshold TPD method. Our experimental data show that after the completion of the first Na layer, 3D crystallites develop on the Na/Ge(100) surface (Stranski-Krastanov growth mode). For Θ > 1 ML, formation, followed by decomposition of a certain Na---Ge surface compound occurs in the temperature range 410–550 K.     

N@C60 and P@C60 as quantum bits

Due to their long electron spin relaxation times, the endohedral fullerenes N@C₆₀ and P@C₆₀ are good candidates for the implementation of qubits in an electron spin quantum computer. A central operation in this context is the rotation of the spin direction by an arbitrary angle. In the present experiment, this nutation behavior was studied in pulsed electron spin resonance measurements. We show that, even at room temperature, about 50 Rabi oscillations (about 100 qubit operations) can be performed without refocusing the spin system, although inhomogeneities are present. A special feature of the group V endohedral fullerenes is the electron spinS=3/2, which complicates the nutation behavior. The zero-field splitting at low temperature gives rise to different nutation frequencies for the (1/2,?1/2) transition and the (±3/2, ±1/2) transitions. The frequency ratio is 2/3^1/2.     

Measuring the force of interaction between a metallic probe and a single molecule

Precision current measurements are recorded at 5 K during the approach and contact between a Pt-inked probe and the carbon-carbon double-bond region of an isolated 1,3-cyclohexadiene molecule chemisorbed on a Si(100) surface. Scanning tunneling spectroscopic data reveal systematic features in the current at specific probe-molecule separations. Aided by density functional theory calculations, we show that these features arise from interaction forces between the probe and molecule, which can be interpreted as the relaxation of the probe-molecule system prior to and during contact.