arXiv subjects

H. C. Ren

Publications and source records attributed to H. C. Ren.

4 recordsLinked to original sources

arXiv2004

Optical Coupling of Mie Particles Adsorbed on a Whispering Gallery Resonator

We present an experimental observation on particles adsorbed to a whispering gallery mode (WGM) optical resonator produced from a glass sphere of about 100 micro meter in radius. For spherical adsorbates of radius about 100 nm, we find a striking nonlinear dependence of the induced wavelength shift on the adsorbed particle density, whereas for Rayleigh particles with dimensions much smaller than the infrared wavelength the dependence is linear with particle density. An explanation of the anamalous effect based on optical coupling between meso-optic adsorbates is suggested.

physics.optics↗

arXiv1997

Comment on "Boson-fermion model beyond the mean-field approximation"

In a recent paper [A.S.Alexandrov, J.Phys.:Condens.Matter 8, 6923 (1996); cond-mat/9603111], it has been suggested that there is no Cooper pairing in boson-fermion models of superconductivity. We show that this conjecture is based on an inconsistent approximation that violates an exact identity. Quite generally, the divergence of the fermion t-matrix (the Thouless criterion) is accompanied by the condensation of a boson mode.

cond-mat.supr-con↗

arXiv1997

Extended bound states and resonances of two fermions on a periodic lattice

The high-$T_c$ cuprates are possible candidates for d-wave superconductivity, with the Cooper pair wave function belonging to a non-trivial irreducible representation of the lattice point group. We argue that this d-wave symmetry is related to a special form of the fermionic kinetic energy and does not require any novel pairing mechanism. In this context, we present a detailed study of the bound states and resonances formed by two lattice fermions interacting via a non-retarded potential that is attractive for nearest neighbors but repulsive for other relative positions. In the case of strong binding, a pair formed by fermions on adjacent lattice sites can have a small effective mass, thereby implying a high condensation temperature. For a weakly bound state, a pair with non-trivial symmetry tends to be smaller in size than an s-wave pair. These and other findings are discussed in connection with the properties of high-$T_c$ cuprate superconductors.

supr-con↗

arXiv1995

Noncompact Lattice Formulation of Gauge Theories

We expand the gauge field in terms of a suitably constructed complete set of Bloch wave functions, each labeled by a band designation $\,n\,$ and a wave number $\,\vec K\,$ restricted to the Brillouin zone. A noncompact formulation of lattice QCD (or QED) can be derived by restricting the expansion only to the $\,0^{th}$-band ($\,n = 0\,$) functions, which are simple continuum interpolations of discrete values associated with sites or links on a lattice. The exact continuum theory can be reached through the inclusion of all $\,n = 0\,$ and $\,n \ne 0\,$ bands, without requiring the lattice size $\,\ell \to 0\,$. This makes it possible, at a nonzero $\,\ell\,$, for the lattice coupling $\,g_\ell\,$ to act as the renormalized continuum coupling. All physical results in the continuum are, of course, independent of $\,\ell\,$.

hep-lat↗