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1.
In this paper, we study quadrature squeezings of
two Bose-Einstein condensates with collision and nonclassical
properties of pair entanglement in four wave mixing in
Bose-Einstein condensates. With the aid of a numerical method, we
find that the two modes (pair entanglement modes) a1 and a2 may exhibit quadrature squeezing, in which they are affected by
the initial phase. It is shown that the two pump modes exhibit
the same super-Poissonian distribution. The analysis for the
mode-mode correlation shows that there always exists a violation
of the Cauchy-Schwartz inequality, which means that correlation
between the two pump modes is nonclassical. 相似文献
2.
3.
Rüegg Ch Furrer A Sheptyakov D Strässle T Krämer KW Güdel HU Mélési L 《Physical review letters》2004,93(25):257201
The condensation of magnetic quasiparticles into the nonmagnetic ground state has been used to explain novel magnetic ordering phenomena observed in quantum spin systems. We present neutron scattering results across the pressure-induced quantum phase transition and for the novel ordered phase of the magnetic insulator TlCuCl3, which are consistent with the theoretically predicted two degenerate gapless Goldstone modes, similar to the low-energy spin excitations in the field-induced case. These novel experimental findings complete the field-induced Bose-Einstein condensate picture and support the recently proposed field-pressure phase diagram common for quantum spin systems with an energy gap of singlet-triplet nature. 相似文献
4.
One introduces a model of the superfluid state of a Bose liquid with repulsion between bosons, in which at T=0, along with a weak single-particle Bose-Einstein condensate, there exists an intensive pair coherent condensate, analogous to the Cooper condensate in a Fermi liquid with attraction between fermions. A closed system of nonlinear integral equations for the normal and anomalous self-energy parts is solved numerically, and a quasiparticle spectrum is obtained, which is in good agreement with the experimental spectrum of elementary excitations in superfluid 4He. It is shown that the roton minimum in the spectrum is associated with the negative minimum of the Fourier component of the pair interaction potential. 相似文献
5.
Hidden duality and its associated instabilities of the spinless Luttinger liquid on lattice are reported. The local quantum fluctuations due to the general multi-particle umklapp and other processes and the long-distance chiral modes compete and as a result produce a hierarchy of exotic charge
density instabilities. Explicit bosonic quantum operators for the local density fluctuations are constructed and are used to make identification of the Luttinger liquid with the classical 2D Coulomb gas with
-term and with the rich hidden duality. 相似文献
6.
M. V. Kuzelev 《Journal of Experimental and Theoretical Physics》2011,112(2):333-343
A nonlinear theory of interaction of two electromagnetic waves with a beam or a gas of spinless charged particles is developed.
The effects of stimulated Compton scattering of electromagnetic waves and stimulated particle pair production (annihilation)
during a collision of two electromagnetic quanta are investigated. Other stimulated processes that can occur only in a medium
and decelerate electromagnetic waves are also considered. The relation between stimulated processes and various types of instabilities
considered in classical electrodynamics of plasmas and plasmalike media is demonstrated. 相似文献
7.
We study a two-dimensional lattice gas of atoms that are photoexcited to Rydberg states in which they interact via the van?der?Waals interaction. We explore the regime of dominant nearest-neighbor interaction where this system is intimately connected with a quantum version of Baxter's hard-squares model. We show that the strongly correlated ground state of the Rydberg gas can be analytically described by a projected entangled pair state that constitutes the ground state of the quantum hard-squares model. This correspondence allows us to identify a phase boundary where the Rydberg gas undergoes a transition from a disordered (liquid) phase to an ordered (solid) phase. 相似文献
8.
The conductance of a weakly interacting electron gas in the presence of a single scatterer is found at arbitrary strength of the scattering potential. At weak interaction one can use a simple renormalization group approach instead of the standard bosonization technique. For a model with spinless electrons this approach allows us to show explicitly the crossover from the Fermi-gas to the low-temperature Luttinger liquid behavior. Deviations from the Luttinger liquid theory are studied for a realistic model of spin-
electrons. 相似文献
9.
10.
《Nuclear Physics B》1995,435(3):567-584
We extend the path-integral approach to bosonization to the case in which the fermionic interaction is non-local. In particular we obtain a completely bosonized version of a Thirring-like model with currents coupled by general (symmetric) bilocal potentials. The model contains the Tomonaga-Luttinger model as a special case; exploiting this fact we study the basic properties of the 1d spinless fermionic gas: fermionic correlators, the spectrum of collective modes, etc. Finally, we discuss the generalization of our procedure to the non-abelian case, thus providing a new tool to be used in the study of 1d many-body systems with spin-flipping interactions. 相似文献
11.
12.
D. N. Sob’yanin 《Bulletin of the Lebedev Physics Institute》2013,40(4):91-96
A theory of Bose-Einstein condensation (BEC) of light in a dye microcavity is developed. The photon polarization degeneracy and the interaction between dye molecules and photons in all of the cavity modes are taken into account. The theory goes beyond the grand canonical approximation and allows one to determine the statistical properties of the photon gas for all numbers of dye molecules and photons at all temperatures, thus describing the microscopic, mesoscopic, and macroscopic light BEC from a general perspective. A universal relation between the degrees of second-order coherence for the photon condensate and the polarized photon condensate is obtained. The photon Bose-Einstein condensate can be used as a new source of nonclassical light. 相似文献
13.
We have studied the properties of the scissors mode of a trapped Bose-Einstein condensate of 87Rb atoms at finite temperature. We measured a significant shift in the frequency of the mode below the hydrodynamic limit and a strong dependence of the damping rate as the temperature increased. We compared our damping rate results to recent theoretical calculations for other observed collective modes, finding a fair agreement. From the frequency measurements we deduce the moment of inertia of the gas and show that it is quenched below the transition point, because of the superfluid nature of the condensed gas. 相似文献
14.
Modulational Instability of Dipolar Bose-Einstein Condensates in Optical Lattices with Three-Body Interactions
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Motivated by the recent experiment [Nature 530(2016) 194] in which a stable droplet in a dipolar quantum gas has been created by the interaction-induced instability, we focus on the modulation instability of an optically-trapped dipolar Bose-Einstein condensate with three-body interaction. Within the mean-field level, we analytically solve the discrete cubic-quintic Gross-Pitaevskii equation with dipole-dipole interaction loaded into a deep optical lattice and show how combined effects of the three-body interaction and dipole-dipole interaction on the condition of modulational instability. Our results show that the interplay of the three-body interaction and dipole-dipole interaction can dramatically change the modulation instability condition compared with the ordinary Gross-Pitaevskii equation. We believe that the predicted results in this work can be useful for the future possible experiment of loading a Bose-Einstein condensate of ~(164)Dy atoms with strong magnetic dipole-dipole interaction into an optical lattice. 相似文献
15.
16.
P.B. Jones 《Physics letters. [Part B]》1976,64(2):230-232
A dilute system of isospin waves in equilibrium with electrons in a neutron lattice should show Bose-Einstein condensation. The weak interaction of the condensate may cause damping of the free precession of neutron stars. 相似文献
17.
H. R. Glyde 《The European physical journal. Special topics》2007,141(1):75-81
We sketch our recent neutron scattering measurements of
the phonon-roton (P-R) modes and Bose-Einstein condensation (BEC) of
liquid 4He in porous media. The aim is to reveal the
interdependence of BEC, well-defined P-R modes and superfluidity in
helium confined to nanoscales and in disorder. In all porous media
investigated to date, we observe well-defined P-R modes above Tc in
the normal liquid phase, up to Tλ. Since well defined P-R modes are
associated with BEC, this suggests that there is BEC above Tc in
porous media. We interpret this as BEC localized to favorable
regions separated by regions of normal fluid. At high pressures, p
≥25 bars, well defined P-R modes are no longer observed at lower
wavevectors, Q ≤1.5 ?. At p ≈39 bars a roton is
no longer observed. Work is in progress to explore whether loss of
modes can be associated with a recently reported Quantum Phase
Transition. 相似文献
18.
The dispersion relation of ripplons on the surface of a two-component liquid has been derived using the hydrodynamic mean-field model, in terms of the interaction pair potentials of the constituent particles. The modes for planar and spherical geometries have been derived explicitly. The formalism is applied to ripples on the surfaces of liquids in which the interparticle interaction is not Coulombic, as also on the surfaces of jellium and on electron-hole droplets. 相似文献
19.
G. Kónya G. Szirmai P. Domokos 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,65(1-2):33-42
We develop a mean-field model describing the Hamiltonian interaction of ultracold atoms and the optical field in a cavity. The Bose-Einstein condensate is properly defined by means of a grand-canonical approach. The model is efficient because only the relevant excitation modes are taken into account. However, the model goes beyond the two-mode subspace necessary to describe the self-organization quantum phase transition observed recently. We calculate all the second-order correlations of the coupled atom field and radiation field hybrid bosonic system, including the entanglement between the two types of fields. 相似文献
20.
Ph. Droz-Vincent 《International Journal of Theoretical Physics》2016,55(9):4124-4141
The relativistic two-body problem is considered for spinless particles subject to an external electromagnetic field. When this field is made of the monochromatic superposition of two counter-propagating plane waves (and provided the mutual interaction between particles is known), it is possible to write down explicitly a pair of coupled wave equations (corresponding to a pair of mass-shell constraints) which takes into account also the field contribution. These equations are manifestly covariant; constants of the motion are exhibited, so one ends up with a reduced problem involving five degrees of freedom. 相似文献