2,058 research outputs found
Peierls instability, periodic Bose-Einstein condensates and density waves in quasi-one-dimensional boson-fermion mixtures of atomic gases
We study the quasi-one-dimensional (Q1D) spin-polarized bose-fermi mixture of
atomic gases at zero temperature. Bosonic excitation spectra are calculated in
random phase approximation on the ground state with the uniform BEC, and the
Peierls instabilities are shown to appear in bosonic collective excitation
modes with wave-number by the coupling between the Bogoliubov-phonon
mode of bosonic atoms and the fermion particle-hole excitations. The
ground-state properties are calculated in the variational method, and,
corresponding to the Peierls instability, the state with a periodic BEC and
fermionic density waves with the period are shown to have a lower
energy than the uniform one. We also briefly discuss the Q1D system confined in
a harmonic oscillator (HO) potential and derive the Peierls instability
condition for it.Comment: 9 pages, 3figure
Critical temperature of Bose-Einstein condensation in trapped atomic Bose-Fermi mixtures
We calculate the shift in the critical temperature of Bose-Einstein
condensation for a dilute Bose-Fermi mixture confined by a harmonic potential
to lowest order in both the Bose-Bose and Bose-Fermi coupling constants. The
relative importance of the effect on the critical temperature of the
boson-boson and boson-fermion interactions is investigated as a function of the
parameters of the mixture. The possible relevance of the shift of the
transition temperature in current experiments on trapped Bose-Fermi mixtures is
discussed.Comment: 15 pages, 2 figures, submitted to J. Phys.
Fluctuations in the formation time of ultracold dimers from fermionic atoms
We investigate the temporal fluctuations characteristic of the formation of
molecular dimers from ultracold fermionic atoms via Raman photoassociation. The
quantum fluctuations inherent to the initial atomic state result in large
fluctuations in the passage time from atoms to molecules. Assuming degeneracy
of kinetic energies of atoms in the strong coupling limit we find that a
heuristic classical stochastic model yields qualitative agreement with the full
quantum treatment in the initial stages of the dynamics. We also show that in
contrast to the association of atoms into dimers, the reverse process of
dissociation from a condensate of bosonic dimers exhibits little passage time
fluctuations. Finally we explore effects due to the non-degeneracy of atomic
kinetic energies.Comment: 7 pages, 6 figure
The Experimental plan of the 4m Resonant Sideband Extraction Prototype for The LCGT
The 4m Resonant Sideband Extraction (RSE) interferometer is a planned prototype of the LCGT interferometer. The aim of the experiment is to operate a powerrecycled Broadband RSE interferometer with suspended optics and to achieve diagonalization of length signals of the central part of the interferometer directly through the optical setup. Details of the 4m RSE interferometer control method as well as the design of the experimental setup will be presented
A one-compartment, direct glucose fuel cell for powering long-term medical implants
We present the operational concept, microfabrication, and electrical performance of an enzyme-less direct glucose fuel cell for harvesting the chemical energy of glucose from body fluids. The spatial concentrations of glucose and oxygen at the electrodes of the one-compartment setup are established by self-organization, governed by the balance of electro-chemical depletion and membrane diffusion. Compared to less stable enzymatic and immunogenic microbial fuel cells, this robust approach excels with an extended life time, the amenability to sterilization and biocompatibility, showing up a clear route towards an autonomous power supply for long-term medical implants without the need of surgical replacement and external refueling. Operating in physiological phosphate buffer solution containing 0.1 wt% glucose and having a geometrical cathode area of 10 cm2, our prototype already delivers 20 µ W peak power over a period of 7 days
Dynamical properties of dipolar Fermi gases
We investigate dynamical properties of a one-component Fermi gas with
dipole-dipole interaction between particles. Using a variational function based
on the Thomas-Fermi density distribution in phase space representation, the
total energy is described by a function of deformation parameters in both real
and momentum space. Various thermodynamic quantities of a uniform dipolar Fermi
gas are derived, and then instability of this system is discussed. For a
trapped dipolar Fermi gas, the collective oscillation frequencies are derived
with the energy-weighted sum rule method. The frequencies for the monopole and
quadrupole modes are calculated, and softening against collapse is shown as the
dipolar strength approaches the critical value. Finally, we investigate the
effects of the dipolar interaction on the expansion dynamics of the Fermi gas
and show how the dipolar effects manifest in an expanded cloud.Comment: 14 pages, 8 figures, submitted to New J. Phy
Bose-Fermi Mixtures in One Dimension
We analyze the phase stability and the response of a mixture of bosons and
spin-polarized fermions in one dimension (1D). Unlike in 3D, phase separation
happens for low fermion densities. The dynamics of the mixture at low energy is
independent of the spin-statistics of the components, and zero-sound-like modes
exist that are essentially undamped.Comment: 5 pages; 1 figur
Control sideband generation for dual-recycled laser interferometric gravitational wave detectors
We present a discussion of the problems associated with generation of multiple control sidebands for length sensing and control of dual-recycled, cavity-enhanced Michelson interferometers and the motivation behind more complicated sideband generation methods. We focus on the Mach–Zehnder interferometer as a topological solution to the problem and present results from tests carried out at the Caltech 40 m prototype gravitational wave detector. The consequences for sensing and control for advanced interferometry are discussed, as are the implications for future interferometers such as Advanced LIGO
Achieving diffraction-limited performance on the Berkeley MET5
The Berkeley MET5, funded by EUREKA, is a 0.5-NA EUV projection lithography tool located at the Advanced Light Source at Berkeley National Lab. Wavefront measurements of the MET5 optic have been performed using a custom in-situ lateral shearing interferometer suitable for high-NA interferometry. In this paper, we report on the most recent characterization of the MET5 optic demonstrating an RMS wavefront 0.31 nm, and discuss the specialized mask patterns, gratings, and illumination geometries that were employed to accommodate the many challenges associated with high-NA EUV interferometry
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