Here is a list of relevant abstracts from the Cornell archives. Perhaps condensed matter specialists do not publish preprints there.
Authors: Zaira Nazario, David I. Santiago
Comments: 4 pages
Subjclass: Soft Condensed Matter
We show that the suppression of light scattering off a Bose Einstein Condensate is equivalent to the Landau argument for superfluidity and thus is a consequence of the {\it Principle of Superfluidity}. The superfluid ground state of a BEC contains nonseparable, nontrivial correlations between the bosons that make up the system, i. e., it is entangled. The correlations in the ground state entangle the bosons into a coherent state for the lowest energy state. The entanglement is so extreme that the bosons that make up the system cannot be excited at long wavenumbers. Their existence at low energies is impossible. Only quantum sound can be excited, i.e. the excitations are Bogolyubov quasiparticles which do not resemble free bosons whatsoever at low energies. This means that the system is superfluid by the Landau argument and the superfluidity is ultimately the reason for suppressed scattering at low wavelengths.
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http://arxiv.org/abs/condmat/0309211
Modified dynamics of weakly coupled BEC's Josephson Junction (BJJ)
Authors: Yuping Huang, Zhensheng Yuan, Linfan Zhu, Linjiao Luo, Xiaojing Liu, Kezun Xu
Comments: 5 pages, 3 figures, submitted to Phys. Rev. A
Subjclass: Soft Condensed Matter
The tunnelling quantum dynamics of bimodal BJJ system is modified through introducing an equilibrium condition, which is based on the assumption that the BJJ is tend to keep on its ground state (with a lowest energy) during the oscillation. The tunnelling dynamics of BJJ with symmetric and asymmetric traps is discussed through numerically solving the modified equations. Stationary states are found to exist in the both BJJs. Compared to previous works, the macroscopic quantum self trapping (MQST) is autoavoided. Meanwhile, it is revealed that the BJJ oscillates with its inherent frequency which is only related to the Josephson energy, which has been testified experimentally in other contexts.
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http://arxiv.org/abs/condmat/0309009
Quantum States of Matter of Simple Bosonic Systems: BEC's, Superfluids and Quantum Solids
Authors: Zaira Nazario, David I. Santiago
Comments: 4 pages, 2 figures
Subjclass: Soft Condensed Matter
The phase diagram of a single component Bose system in a lattice at zero temperature is obtained. We calculate the variational energies for the Mott insulating and superfluid phases. Below a certain critical density, which depends monotonically on the well depth of the lattice, the Mott insulating phase is stable over the superfluid phase for low enough tunelling amplitude regardless of whether the number of bosons is or is not incommensurate with the lattice. The transition is discontinuous as the superfluid order parameter jumps from a finite value to zero at the Mott transition.
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http://arxiv.org/abs/condmat/0308005
BCS and BEC Finally Unified: A Brief Review
Authors: J. Batle, M. Casas, M. Fortes, M. de Llano, O. Rojo, F.J. Sevilla, M.A. Solis, V.V.Tolmachev
Comments: 17 pages including 4 figures. To be published in Cond. Matt. Theories Vol. 18, Ed. Joao da Providencia ((Nova Science Publisher, Inc., N. Y., 200?)
Subjclass: Superconductivity
We review efforts to unify both the Bardeen, Cooper and Schrieffer (BCS) and BoseEinstein condensation (BEC) pictures of superconductivity. We have finally achieved this in terms of a "\textit{complete} bosonfermion (BF) model" (CBFM) that reduces in special cases to all the main continuum (as opposed to "spin") statistical theories of superconductivity. Our BF model is "complete" in the sense that not only twoelectron (2e) but also twohole (2h) Cooper pairs (CPs) are allowed in arbitrary proportions. In contrast, BCSBogoliubov theorywhich can also be considered as the theory of a mixture of kinematically independent electrons, 2e and 2hCPsallows only equal, 50%50%, mixtures of the two kinds of CPs. This is obvious from the perfect symmetry about $\mu$, the electron chemical potential, of the wellknown Bogoliubov $v^{2}(\epsilon)$ and $u^{2}(\epsilon)$ coefficients, where $\epsilon$ is the electron energy. The CBFM is then applied to see: a) whether the BCS model interaction for the electronphonon dynamical mechanism is sufficient to predict the unusually high values of $T_{c}$ (in units of the Fermi temperature) of $\simeq 0.010.1$ exhibited by the socalled ``exotic'' superconductors \cite{Brandow} in both 2D and 3Drelative to the low values of $\lesssim 10^{3}$ more or less correctly predicted by BCS theory for conventional, elemental superconductors; and b) whether it can at least suggest, if not explain, why "hole superconductors" have higher $T_{c}$'s.
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http://arxiv.org/abs/condmat/0211456
Application to a BEC in an Optical Potential
Authors: Y.B. Band, I. Towers, B. Malomed
Comments: 14 pages, 5 figures
Subjclass: Soft Condensed Matter
We present semiclassical descriptions of BoseEinstein condensates for configurations with spatial symmetry, e.g., cylindrical symmetry, and without any symmetry. The description of the cylindrical case is quasionedimensional (Q1D), in the sense that one only needs to solve an effective 1D nonlinear Schrodinger equation, but the solution incorporates correct 3D aspects of the problem. The solution in classically allowed regions is matched onto that in classically forbidden regions by a connection formula that properly accounts for the nonlinear meanfield interaction. Special cases for vortex solutions are treated too. Comparisons of the Q1D solution with full 3D and ThomasFermi ones are presented.
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http://arxiv.org/abs/condmat/0207739
Spin1/2 Collective Excitations in BEC of Interacting Spin1 Atoms
Authors: Fei Zhou (ITP, Utrecht)
Comments: 5 pages
Subjclass: Statistical Mechanics; Strongly Correlated Electrons
We construct spin1/2 collective excitations in BEC of interacting spin1 atoms. These excitations exist in states with a maximal global degeneracy. The stability and energy of these objects are determined by interactions with spin fluctuations and are studied based on a duality relation between hypermonopoles and magnetic monopoles in physical space.
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http://arxiv.org/abs/condmat/0106133
Novel Theory for Topological Structure of Vortices in BEC
Authors: Yishi Duan, Xin Liu, Pengming Zhang
Subjclass: Mesoscopic Systems and Quantum Hall Effect
By making use of the $\phi $mapping topological current theory, a novel expression of $\nabla \times \vec{V}$ in BEC is obtained, which reveals the inner topological structure of vortex lines characterized by Hopf indices and Brouwer degrees. This expression is just that formula Landau and Feynman expected to find out long time ago. In the case of superconductivity, the decomposition theory of U(1) gauge potential in terms of the condensate wave function gives a rigorous proof of London assumption, and shows that each vortex line should carry a quantized flux. The $\phi $mapping topological current theory of $\nabla \times \vec{V}$ can also gives a precise bifurcation theory of vortex lines in BEC.
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http://arxiv.org/abs/condmat/0106103
