Statics and dynamics of phase segregation in multicomponent fermion gas

We investigate the statics and dynamics of spatial phase segregation process of a mixture of fermion atoms in a harmonic trap using the density functional theory. The kinetic energy of the fermion gas is written in terms of the density and its gradients. Several cases have been studied by neglecting the gradient terms (the Thomas-Fermi limit) which are then compared with the Monte-Carlo results using the full gradient corrected kinetic energy. A linear instability analysis has been performed using the random-phase approximation. Near the onset of instability, the fastest unstable mode for spinodal decomposition is found to occur at $q=0$. However, in the strong coupling limit, many more modes with $q\approx K_F$ decay with comparable time scales.Comment: 14 figure

Role of Interlayer Coupling on the Evolution of Band Edges in Few-Layer Phosphorene

Using first-principles calculations, we have investigated the evolution of band-edges in few-layer phosphorene as a function of the number of P layers. Our results predict that monolayer phosphorene is an indirect band gap semiconductor and its valence band edge is extremely sensitive to strain. Its band gap could undergo an indirect-to-direct transition under a lattice expansion as small as 1% along zigzag direction. A semi-empirical interlayer coupling model is proposed, which can well reproduce the evolution of valence band-edges obtained by first-principles calculations. We conclude that the interlayer coupling plays a dominated role in the evolution of the band-edges via decreasing both band gap and carrier effective masses with the increase of phosphorene thickness. A scrutiny of the orbital-decomposed band structure provides a better understanding of the upward shift of valence band maximum surpassing that of conduction band minimum.Comment: 25 pages, 9 figure

Hysteretic current-voltage characteristics and resistance switching at an epitaxial oxide Schottky junction SrRuO3_{3}/SrTi0.99_{0.99}Nb0.01_{0.01}O3_{3}

Transport properties have been studied for a perovskite heterojunction consisting of SrRuO$_{3}$ (SRO) film epitaxially grown on SrTi$_{0.99}$Nb$_{0.01}$O$_{3}$ (Nb:STO) substrate. The SRO/Nb:STO interface exhibits rectifying current-voltage ($I$-$V$) characteristics agreeing with those of a Schottky junction composed of a deep work-function metal (SRO) and an $n$-type semiconductor (Nb:STO). A hysteresis appears in the $I$-$V$ characteristics, where high resistance and low resistance states are induced by reverse and forward bias stresses, respectively. The resistance switching is also triggered by applying short voltage pulses of 1 $\mu$s - 10 ms duration.Comment: 3 pages, 3 figures, Appl. Phys. Lett., in pres

First-principles study of the onset of noncollinearity in Mnn clusters: Magnetic arrangements in Mn5 and Mn6

First-principles theoretical investigations of the noncollinearity of atomic spin moments in manganese clusters have been carried out within a gradient-corrected density-functional approach. Our studies on Mn5 and Mn6 include investigation of both collinear and noncollinear arrangements. It is shown that while the atomic structure of the ground state of Mn5 is a triangular bipyramid, the collinear and noncollinear arrangements have comparable energies and hence are degenerate. For Mn6, while the ground state has a square bipyramid arrangement, the noncollinear configuration is most stable making it the smallest cluster to feature a noncollinear ground state. The results are discussed in view of the recent experimental Stern-Gerlach profiles