凝聚态物理
Using density functional theory, we investigate the structure of mixed $^3$He$_{N_3}$-$^4$He$_{N_4}$ droplets with an embedded impurity (Xe atom or HCN molecule) which pins a quantized vortex line. We find that the…
Helium nanodroplets and trapped Bose-Einstein condensates in dilute atomic gases offer complementary views of fundamental aspects of quantum many-body systems. We discuss analogies and differences, stressing their common theoretical…
We study the relation between stock price changes and the difference in the number of sell and buy orders. Using a soft spin model, we describe the price impact of order imbalances and find an analogy to the fluctuation-dissipation theorem…
We investigate the groundstates of weakly interacting bosons in a rotating trap as a function of the number of bosons, $N$, and the average number of vortices, $N_V$. We identify the filling fraction $\nu\equiv N/N_V$ as the parameter…
We calculate the spectral density of voltage fluctuations in a Single Electron Transistor (SET), biased to operate in a transport mode where tunneling events are correlated due to Coulomb interaction. The whole spectrum from low frequency…
We study a dynamical system model of an idiotypic immune network with a small number of degrees of freedom, mainly focusing on the effect of a threshold above which antibodies can recognise antibodies. The response of the system to…
The application of the Schwinger-boson transformation to quantum Heisenberg magnets is briefly reviewed, beginning with the derivation of a rotationally invariant mean-field theory. The inclusion of Gaussian fluctuations is discussed in…
We calculate the energy and condensate fraction for a dense system of bosons interacting through an attractive short range interaction with positive s-wave scattering length $a$. At high densities, $n>>a^{-3}$, the energy per particle,…
In magnetic fields applied parallel to the anisotropy axis, the relaxation of the magnetization of Mn$_{12}$ measured for different sweep rates is shown to collapse onto a single scaled curve. The form of the scaling implies that the…
We investigate numerically the failure process when two elastic media, one hard and one soft that have been glued together thus forming a common interface, are pulled apart. We present three main results: (1) The area distribution of…
We study theoretically the thermodynamics, over a broad temperature range (5 C to 125 C), related to hydrated water upon protein unfolding. The hydration effect is modeled as interacting dipoles in an external field, mimicking the influence…
A density functional theory of ferromagnetism in heterostructures of compound semiconductors doped with magnetic impurities is presented. The variable functions in the density functional theory are the charge and spin densities of the…
We summarize the different puzzles raised by aging experiments of spin-glasses and their various interpretations. We try to reconcile the `real space', droplet like pictures with the hierarchical pictures that have been proposed in the…
We present a systematic study of ground state and spectroscopic properties of many-electron nanoscopic quantum rings. Addition energies at zero magnetic field (B) and electro-chemical potentials as a function of $B$ are given for a ring…
This paper examines the parameter regimes in which coupled atomic and molecular Bose-Einstein condensates do not obey the Gross-Pitaevskii equation. Stochastic field equations for coupled atomic and molecular condensates are derived using…
Localization of acoustic waves in a one dimensional water duct containing many randomly distributed air filled blocks is studied. Both the Lyapunov exponent and its variance are computed. Their statistical properties are also explored…
Collisional avalanches are identified to be responsible for an 8-fold increase of the initial loss rate of a large 87-Rb condensate. We show that the collisional opacity of an ultra-cold gas exhibits a critical value. When exceeded, losses…
Exact quantum integrability is established for a class of multi-chain electron models with correlated hopping and spin models with interchain interactions, by constructing the related Lax operators and R-matrices through twisting and gauge…
We study a general model for non-gaussian $1/f$ noise based on an infinite range quantum Ising spin system in the paramagnetic state, or equivalently, interacting two-level classical fluctuators. We identify a dilatation interaction term in…
The nature of the correlated electron gas and its response to photo-injected electron-hole pairs in nominally undoped and modulation-doped multiple quantum-well (MQW) structures was studied by experiment and theory, revealing a new type of…