Tuning a magnetic Feshbach resonance with spatially modulated laser light

We theoretically investigate the control of a magnetic Feshbach resonance using a bound-to-bound molecular transition driven by spatially modulated laser light. Due to the spatially periodic coupling between the ground and excited molecular states, there exists a band structure of bound states, which can uniquely be characterized by some extra bumps in radio-frequency spectroscopy. With the increasing of coupling strength, the series of bound states will cross zero energy and directly result in a number of scattering resonances, whose position and width can be conveniently tuned by the coupling strength of the laser light and the applied magnetic field (i.e., the detuning of the ground molecular state). In the presence of the modulated laser light, universal two-body bound states near zero-energy threshold still exist. However, compared with the case without modulation, the regime for such universal states is usually small. An unified formula which embodies the influence of the modulated coupling on the resonance width is given. The spatially modulated coupling also implies a local spatially varying interaction between atoms. Our work proposes a practical way of optically controlling interatomic interactions with high spatial resolution and negligible atomic loss.Comment: 9pages, 5figur

Low energy exciton states in a nanoscopic semiconducting ring

We consider an effective mass model for an electron-hole pair in a simplified confinement potential, which is applicable to both a nanoscopic self-assembled semiconducting InAs ring and a quantum dot. The linear optical susceptibility, proportional to the absorption intensity of near-infrared transmission, is calculated as a function of the ring radius $$. Compared with the properties of the quantum dot corresponding to the model with a very small radius $R_0$, our results are in qualitative agreement with the recent experimental measurements by Pettersson {\it et al}.Comment: 4 pages, 4 figures, revised and accepted by Phys. Rev.

Mesoscopic Kondo screening effect in a single-electron transistor embedded in a metallic ring

We study the Kondo screening effect generated by a single-electron transistor or quantum dot embedded in a small metallic ring. When the ring circumference $L$ becomes comparable to the fundamental length scale $\xi_K^0=\hbar \upsilon _F/T_K^0$ associated with the {\it bulk} Kondo tempe the Kondo resonance is strongly affected, depending on the total number of electrons ({\it modulo} 4) and magnetic flux threading the ring. The resulting Kondo-assisted persistent currents are also calculated in both Kondo and mixed valence regimes, and the maximum values are found in the crossover region.Comment: 4 pages, Revtex, 6 figures, more references are include

Valence bond spin liquid state in two-dimensional frustrated spin-1/2 Heisenberg antiferromagnets

Fermionic valence bond approach in terms of SU(4) representation is proposed to describe the $J_{1}-J_{2}$ frustrated Heisenberg antiferromagnetic (AF) model on a {\it bipartite} square lattice. A uniform mean field solution without breaking the translational and rotational symmetries describes a valence bond spin liquid state, interpolating the two different AF ordered states in the large $J_{1}$ and large $J_{2}$ limits, respectively. This novel spin liquid state is gapless with the vanishing density of states at the Fermi nodal points. Moreover, a sharp resonance peak in the dynamic structure factor is predicted for momenta ${\bf q}=(0,0)$ and $(\pi ,\pi)$ in the strongly frustrated limit $J_{2}/J_{1}\sim 1/2$, which can be checked by neutron scattering experiment.Comment: Revtex file, 4 pages, 4 figure

Chemical dynamics of the Changjiang estuary

【Abstract】A reconnaissance of the chemical dynamics of the estuary and plume of the Changjiang was carried out on cruises in the summer of 1980 and the winter of 1981. In summer vigorous turbulence in the main channel of the inner estuary maintains high concentrations of suspended material in the surface layers which suppresses biological activity. Plankton blooms occur only on the inner shelf at salinities greater than about 20 ppt. In winter there is no significant photosynthetic activity over the entire mixing zone. Therefore a wide variety of inorganic processes can be studied in detail. Of the nutrients, nitrate is present in the river in very high concentrations and suffers only minor depletion in the biologically active areas. The distribution of silica is similar. Phosphate shows major release from the suspended particles and complete depletion in the plankton blooms. Among the trace elements, iron decreases rapidly to 5 ppt, beyond which mixing is conservative; comparison with the nutrient trends indicates that the element is chemically adsorbed onto the particulates. In contrast manganese undergoes desorption out to about 12 ppt beyond which it mixes conservatively. Copper and beryllium behave conservatively over the entire mixing zone while nickel and barium are desorbed rapidly at low salinity. Cadmium is undetectable in the river waters (< 10pmol kg−1) but displays a broad desorptive maximum at intermediate salinities in the mixing zone. These data allow fluxes to be calculated for the net transport of dissolved material from the Changjiang Basin to the surface waters of the East China Sea and their comparison with those of other large rivers of the world