Search results for "moment"
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Exploring Quantum Matter with Ultracold Atoms in Optical Lattices
2005
Publisher Summary This chapter explores quantum matter with ultracold atoms in optical lattices. The chapter focuses on bosonic atoms in optical lattices and on the regime where strong correlations between the atoms become important. In the interaction of atoms with coherent light fields, two fundamental forces arise. The Doppler force is dissipative in nature and can be used to efficiently laser cool a gas of atoms and relies on the radiation pressure together with spontaneous emission. The dipole force creates a purely conservative potential in which the atoms can move. No cooling can be realized with this dipole force, however if the atoms are cold enough initially, they may be trapped i…
Entangled states of trapped ions allow measuring the magnetic field gradient produced by a single atomic spin
2012
Using trapped ions in an entangled state we propose detecting a magnetic dipole of a single atom at distance of a few $\mu$m. This requires a measurement of the magnetic field gradient at a level of about 10$^{-13}$ Tesla/$\mu$m. We discuss applications e.g. in determining a wide variation of ionic magnetic moments, for investigating the magnetic substructure of ions with a level structure not accessible for optical cooling and detection,and for studying exotic or rare ions, and molecular ions. The scheme may also be used for measureing spin imbalances of neutral atoms or atomic ensembles trapped by optical dipole forces. As the proposed method relies on techniques well established in ion t…
Production and study of spinor condensates of <sup>87</sup>Rb released from a magnetic trap
2009
We report on our study of spinor condensates in the F=2 state of 87Rb produced in an atomic cloud expanding after releasing from a magnetic trap. The experiments are conducted in the setup described in Ref. [1].
Momentum-dependent pseudogaps in the half-filled two-dimensional Hubbard model
2012
We compute unbiased spectral functions of the two-dimensional Hubbard model by extrapolating Green functions, obtained from determinantal quantum Monte Carlo simulations, to the thermodynamic and continuous time limits. Our results clearly resolve the pseudogap at weak to intermediate coupling, originating from a momentum selective opening of the charge gap. A characteristic pseudogap temperature T*, determined consistently from the spectra and from the momentum dependence of the imaginary-time Green functions, is found to match the dynamical mean-field critical temperature, below which antiferromagnetic fluctuations become dominant. Our results identify a regime where pseudogap physics is …
Quantum critical point in ferromagnet
2008
Abstract The heavy-fermion metal CePd 1 - x Rh x can be tuned from ferromagnetism at x = 0 to non-magnetic state at the critical concentration x c . The non-Fermi liquid behavior at x ≃ x c is recognized by power law dependence of the specific heat C ( T ) given by the electronic contribution, susceptibility χ ( T ) and volume expansion coefficient α ( T ) at low temperatures: C / T ∝ χ ( T ) ∝ α ( T ) / T ∝ 1 / T . We show that this alloy exhibits a universal thermodynamic non-Fermi liquid behavior independent of magnetic ground state. This can be well understood utilizing the quasiparticle picture and the concept of fermion condensation quantum phase transition at the density ρ = p F 3 / …
Generation of Non-Classical States through QND-like Processes
2007
In the spirit of quantum nondemolition measurement we show that repeatedly measuring the atomic state of a trapped ion subjected to suitable vibronic couplings it is possible to extract interesting nonclassical states. The possibility of generating angular momentum Schrödinger cat is demonstrated.
Epitaxy of thin films of the Heusler compound
2007
Abstract Epitaxial thin films of the highly spin polarized Heusler compound Co 2 Cr 0.6 Fe 0.4 Al are deposited by DC magnetron sputtering. It is shown by XRD and TEM investigations how the use of an Fe buffer layer on MgO(1 0 0) substrates supports the growth of highly ordered Co 2 Cr 0.6 Fe 0.4 Al at low deposition temperatures. The as-grown samples show a relatively large ordered magnetic moment of μ ≃ 3.0 μ B / f . u . providing evidence for a low level of disorder.
Investigation of a novel material for magnetoelectronics: Co2Cr0.6Fe0.4Al
2003
Heusler compounds are promising candidates for future spintronics device applications. The electronic and magnetic properties of Co2Cr0.6Fe0.4Al, an electron-doped derivative of Co2CrAl, are investigated using circularly polarized synchrotron radiation and photoemission electron microscopy (PEEM). Element specific imaging reveals needle shaped Cr rich phases in a homogeneous bulk of the Heusler compound. The ferromagnetic domain structure is investigated on an element-resolved basis using x-ray magnetic circular dichroism (XMCD) contrast in PEEM. The structure is characterized by micrometre-size domains with a superimposed fine ripple structure; the lateral resolution in these images is abo…
EMI Analysis in Electrical Drives under Lightning Surge Conditions
2012
In this paper, a complete model of a power drive system including the earth electrodes is proposed to evaluate electromagnetic conducted interference due to lightning pulses. Circuit model of a power drive system is joined with a full-wave approach for the simulation of the time behavior of the grounding system. The proposed model enables to predict the electromagnetic conducted interference generated in the power drive system when lightning conditions involve the earth electrodes.
Fractional visco-elastic Euler–Bernoulli beam
2013
Abstract Aim of this paper is the response evaluation of fractional visco-elastic Euler–Bernoulli beam under quasi-static and dynamic loads. Starting from the local fractional visco-elastic relationship between axial stress and axial strain, it is shown that bending moment, curvature, shear, and the gradient of curvature involve fractional operators. Solution of particular example problems are studied in detail providing a correct position of mechanical boundary conditions. Moreover, it is shown that, for homogeneous beam both correspondence principles also hold in the case of Euler–Bernoulli beam with fractional constitutive law. Virtual work principle is also derived and applied to some c…