Investigations with various inner shielding distance tests for a novel coupler-based CPT system applied for electric vehicles using electromagnetic resonant coupling and aluminium shielding material

Contactless power transfer (CPT) technology development has been driven rapidly over the past decade by the world-wide trends towards new energy explorations, and numerous reports have been presented in this area. This paper focuses on passive magnetic shielding, which acts as one of the major factors mainly determining the overall CPT system performance when discussing electromagnetic field flux distribution and its real-time effects on magnetic resonant coupling. As a well performance conductive metallic material, aluminium has been adopted to be a passive shielding material in the designed novel H-shape coupler CPT system in this paper, in order to evaluate and find out the optimal inner shielding distance in between the coil and the inner shielding shell. Three inner shielding distances are applied and analyzed across a critical range of system operating frequency, by which the actual CPT system performance differences from perspectives of electromagnetics and power electronics have been illustrated and compared. As a result, it can be noticed that the 15-mm inner shielding gap CPT model is able to yield an optimal system performance with a maximum system efficiency, peak system output RMS power of over 36% and 22 kW, respectively, which also shows an optimal capability to address major concerns over electric vehicle contactless charging. Besides, along with the electromagnetic field parameters generated in the model, such as actual real-time values of flux linkage, magnetic flux density and field strength, it can be found that the 15-mm inner shielding gap prototype is able to achieve better overall magnetic field performance than 5-mm and 25-mm inner shielding distance CPT models

Conditions for entanglement transformation between a class of multipartite pure states with generalized Schmidt decompositions

In this note we generalize Nielsen's marjoization criterion for the convertibility of bipartite pure states [Phys. Rev. Lett \textbf{83}, 436(1999)] to a special class of multipartite pure states which have generalized Schmidt decompositions.Comment: 3 pages (Revetex 4), no figures. A brief note on entanglement transformation. Comments are welcom

Dynamical Response of Fermi Condensate to Varying Magnetic Fields

We investigate the dynamical response of strongly interacting ultra-cold fermionic atoms near Feshbach resonance to varying magnetic fields. Following the experimental practices, we calculate the response of the atoms to oscillating and to linearly ramped magnetic fields respectively. For oscillating magnetic fields, depending on the frequencies and the amplitudes of the oscillations, the response of the pair excitation gap shows either linear or rich non-linear behaviour. In addition, both the spectral studies through the linear response theory and the time-domain simulations suggest the existence of a resonant frequency corresponding to the pair dissociation threshold. For linearly ramped magnetic fields, the response of the excitation gap shows damped oscillations. The final value of the excitation gap depends on the rate of the field sweep.Comment: 6 pages, 6 figure

Detecting the breached pair phase in a polarized ultracold Fermi gas

We propose a method for the experimental detection of a new quantum phase, the breached pair state, in a strongly interacting ultracold Fermi gas with population imbalance. We show that through the time-of-flight Raman imaging, the presence of such a phase can be unambiguously determined with a measurement of the momentum-space phase separation of the minority spin component. To guide the experimental efforts, the momentum-space density profiles are calculated under typical experimental conditions.Comment: 4 pages, 3 figures, replaced with the published versio

Trapped Fermions across a Feshbach resonance with population imbalance

We investigate the phase separation of resonantly interacting fermions in a trap with imbalanced spin populations, both at zero and at finite temperatures. We directly minimize the thermodynamical potential under the local density approximation instead of using the gap equation, as the latter may give unstable solutions. On the BEC side of the resonance, one may cross three different phases from the trap center to the edge; while on the BCS side or at resonance, typically only two phases show up. We compare our results with the recent experiment, and the agreement is remarkable.Comment: 4 pages, 3 figures, replaced with the published versio

BCS-BEC crossover and quantum phase transition for 6Li and 40K atoms across Feshbach resonance

We systematically study the BCS-BEC crossover and the quantum phase transition in ultracold 6Li and 40K atoms across a wide Feshbach resonance. The background scattering lengths for 6Li and 40K have opposite signs, which lead to very different behaviors for these two types of atoms. For 40K, both the two-body and the many-body calculations show that the system always has two branches of solutions: one corresponds to a deeply bound molecule state; and the other, the one accessed by the current experiments, corresponds to a weakly bound state with population always dominantly in the open channel. For 6Li, there is only a unique solution with the standard crossover from the weakly bound Cooper pairs to the deeply bound molecules as one sweeps the magnetic field through the crossover region. Because of this difference, for the experimentally accessible state of 40K, there is a quantum phase transition at zero temperature from the superfluid to the normal fermi gas at the positive detuning of the magnetic field where the s-wave scattering length passes its zero point. For 6Li, however, the system changes continuously across the zero point of the scattering length. For both types of atoms, we also give detailed comparison between the results from the two-channel and the single-channel model over the whole region of the magnetic field detuning.Comment: 7 pages, 6 figure

Effective Hamiltonian for fermions in an optical lattice across Feshbach resonance

We derive the Hamiltonian for cold fermionic atoms in an optical lattice across a broad Feshbach resonance, taking into account of both multiband occupations and neighboring-site collisions. Under typical configurations, the resulting Hamiltonian can be dramatically simplified to an effective single-band model, which describes a new type of resonance between the local dressed molecules and the valence bond states of fermionic atoms at neighboring sites. On different sides of such a resonance, the effective Hamiltonian is reduced to either a t-J model for the fermionic atoms or an XXZ model for the dressed molecules. The parameters in these models are experimentally tunable in the full range, which allows for observation of various phase transitions.Comment: 5 pages, 2 figure