A Note on Near-factor-critical Graphs

A near-factor of a finite simple graph $G$ is a matching that saturates all vertices except one. A graph $G$ is said to be near-factor-critical if the deletion of any vertex from $G$ results in a subgraph that has a near-factor. We prove that a connected graph $G$ is near-factor-critical if and only if it has a perfect matching. We also characterize disconnected near-factor-critical graphs.Comment: 4 page

Rashba Spin Interferometer

A spin interferometer utilizing the Rashba effect is proposed. The novel design is composed of a one-dimensional (1D) straight wire and a 1D half-ring. By calculating the norm of the superposed wave function, we derive analytical expressions to describe the spin interference spectrum as a function of the Rashba coupling strength. Presented spin interference results are identified to include (i) the quantum-mechanical 4pi rotation effect, (ii) geometric effect, and (iii) Shubnikov-de Haas-like beating effect.Comment: 3 pages, 3 figures, appears in the proceedings of the 10th Joint MMM/Intermag Conferenc

Quantum World-line Monte Carlo Method with Non-binary Loops and Its Application

A quantum world-line Monte Carlo method for high-symmetrical quantum models is proposed. Firstly, based on a representation of a partition function using the Matsubara formula, the principle of quantum world-line Monte Carlo methods is briefly outlined and a new algorithm using non-binary loops is given for quantum models with high symmetry as SU(N). The algorithm is called non-binary loop algorithm because of non-binary loop updatings. Secondary, one example of our numerical studies using the non-binary loop updating is shown. It is the problem of the ground state of two-dimensional SU(N) anti-ferromagnets. Our numerical study confirms that the ground state in the small N <= 4 case is a magnetic ordered Neel state, but the one in the large N >= 5 case has no magnetic order, and it becomes a dimer state.Comment: 14 pages, 5 figures, Invited talk at the 18th Annual Workshop on Recent Developments of Computer Simulation Studies in Condensed Matter Physics, Athens, 7-11 March, 200

Broken spin-Hall accumulation symmetry by magnetic field and coexisted Rashba and Dresselhaus interactions

The spin-Hall effect in the two-dimensional electron gas (2DEG) generates symmetric out-of-plane spin Sz accumulation about the current axis in the absence of external magnetic field. Here we employ the real space Landauer-Keldysh formalism [B. K. Nikolic et al., Phys. Rev. Lett. 95, 046601 (2005); Phys. Rev. B 73, 075303 (2006)] by considering a four-terminal setup to investigate the circumstances in which this symmetry is broken. For the absence of Dresselhaus interaction, starting from the applied out-of-plane B corresponding to Zeeman splitting energy 0 - 0.5 times the Rashba hopping energy tR, the breaking process is clearly seen. The influence of the Rashba interaction on the magnetization of the 2DEG is studied herein. For coexisted Rashba tR and Dresselhaus tD spin-orbit couplings in the absence of B, interchanging tR and tD reverses the entire accumulation pattern.Comment: 3 pages, 2 figures, appears in the proceedings of 10th MMM/INTERMAG conferenc

Spatial and Temporal Distribution of Trace Metals (Cd, Cu, Ni, Pb, and Zn) in Coastal Waters off the West Coast of Taiwan

Surface water samples were collected along the west coast of Taiwan during two expedition cruises which represent periods of different regional climatic patterns. Information on hydrochemical parameters such as salinity, nutrients, suspended particulate matter (SPM), and Chlorophyll a concentrations were obtained, and dissolved and particulate trace metal (Cd, Cu, Ni, Pb, and Zn) concentrations were determined. Spatial variations were observed and the differences were attributed to (1) influence of varying extents of terrestrial inputs from the mountainous rivers of Taiwan to the coast, and (2) urbanization and industrialization in different parts of the island. Geochemical processes such as desorption (Cd) and adsorption to sinking particles (Pb) also contributed to the variability of trace metal distributions in coastal waters. Results showed temporal variations in chemical characteristics in coastal waters as a consequence of prevailing monsoons. During the wet season when river discharges were higher, the transport of particulate metals was elevated due to increased sediment loads. During the dry season, lower river discharges resulted in a lesser extent of estuarine dilution effect for chemicals of anthropogenic sources, indicated by higher dissolved concentrations present in coastal waters associated with slightly higher salinity