0000000000123216

AUTHOR

M. Saarela

showing 3 related works from this author

CONDENSATE FRACTION IN THE DYNAMIC STRUCTURE FUNCTION OF BOSE FLUIDS

2007

We present results on the behavior of the dynamic structure function in the short wave length limit using the equation of motion method. The one-body continuity equation defines the self-energy, which becomes a functional of the fluctuating two-body correlation function. We evaluate the self-energy in this limit and show that sum rules up to the second moment, which requires the self-energy in the short wave length limit and zero frequency to be proportional to the kinetic energy per particle, are exactly satisfied. We compare our results with the impulse approximation and calculate the condensate fraction. An analytic expression for the momentum distribution is also derived.

PhysicsWavelengthClassical mechanicsContinuity equationMathematical analysisStructure functionSecond moment of areaEquations of motionStatistical and Nonlinear PhysicsImpulse (physics)Condensed Matter PhysicsKinetic energySuperfluid helium-4International Journal of Modern Physics B
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Structure of metastable 2D liquid helium

2007

We present diffusion Monte Carlo (DMC) results on a novel, superfluid phase in two-dimensional 4He at densities higher than 0.065 A-2, which is very close to the freezing density. The new phase has anisotropic, hexatic orbital order, but the single-particle density remains constant. By increasing density the hexatic superfluid forms a metastable state, which lies above the crystal ground state in energy. This implies that the liquid-solid phase transition takes place in two stages: a second-order phase transition from the isotropic superfluid to the hexatic superfluid, followed by a first-order transition that localizes atoms into the triangular crystal order.

Condensed Matter::Quantum GasesPhase transitionMaterials scienceCondensed matter physicsStatistical Mechanics (cond-mat.stat-mech)Liquid heliumCondensed Matter::OtherGeneral Physics and AstronomyFOS: Physical scienceslaw.inventionCondensed Matter - Other Condensed MatterSuperfluidityCrystalCondensed Matter::Soft Condensed MatterlawPhase (matter)MetastabilityDiffusion Monte CarloGround stateCondensed Matter - Statistical MechanicsOther Condensed Matter (cond-mat.other)
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DYNAMIC STRUCTURE FUNCTION OF QUANTUM BOSE SYSTEMS: CONDENSATE FRACTION AND MOMENTUM DISTRIBUTION

2008

We present results on the behavior of the dynamic structure function in the short wave length limit using the equation of motion method. Within this framework we study the linear response of a quantum system to an infinitesimal external perturbation by direct minimization of the action integral. As a result we get a set of coupled continuity equations which define the self-energy. We evaluate the self-energy and the dynamic structure function in the short wavelength limit and show that sum rules up to the third moment are fulfilled. This implies, for instance, that the self-energy at short wavelengths and zero frequency is proportional to the kinetic energy per particle. An essential featu…

PhysicsScatteringPhononMonte Carlo methodEquations of motionStatistical and Nonlinear PhysicsCondensed Matter PhysicsKinetic energyAction (physics)MomentumWavelengthQuantum electrodynamicsQuantum systemLimit (mathematics)Statistical physicsQuantumCondensed Matter Theories
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