Charge neutralization in vacuum for non-conducting and isolated objects using directed low-energy electron and ion beams

We propose using ions and electrons of energy 1 eV–10 eV for neutralizing the charges on the non-conducting or isolated surfaces of high-sensitivity experiments. The mirror surfaces of the test masses of the laser interferometer gravitational observatory are used as an example of the implementation of this method. By alternatively directing beams of positive and negative charges towards the mirror surfaces, we ensure the neutralization of the total charge as well as the equalization of the surface charge distribution to within a few eV of the potential of the ground reference of the vacuum system. This method is compatible with operation in high vacuum, does not require measuring the potential of the mirrors and is expected not to damage sensitive optical surfaces

Pitfalls in the analysis of low-temperature thermal conductivity of high-Tc cuprates

Recently, it was proposed that phonons are specularly reflected below about 0.5 K in ordinary single-crystal samples of high-T_c cuprates, and that the low-temperature thermal conductivity should be analyzed by fitting the data up to 0.5 K using an arbitrary power law. Such an analysis yields a result different from that obtained from the conventional analysis, in which the fitting is usually restricted to a region below 0.15 K. Here we show that the proposed new analysis is most likely flawed, because the specular phonon reflection means that the phonon mean free path \ell gets LONGER than the mean sample width, while the estimated \ell is actually much SHORTER than the mean sample width above 0.15 K.Comment: 4 pages, 1 figure; manuscript for the Proceedings of LEHTSC2007 to be published in Journal of Physics: Conference Serie

A Millikelvin Scanned Probe for Measurement of Nanostructures

We demonstrate a scanning force microscope, based upon a quartz tuning fork, that operates below 100 mK and in magnetic fields up to 6 T. The microscope has a conducting tip for electrical probing of nanostructures of interest, and it incorporates a low noise cryogenic amplifier to measure both the vibrations of the tuning fork and the electrical signals from the nanostructures. At millikelvin temperatures the imaging resolution is below 1 um in a 22 um x 22 um range, and a coarse motion provides translations of a few mm. This scanned probe is useful for high bandwidth measurement of many high impedance nanostructures on a single sample. We show data locating an SET within an array and measure its coulomb blockade with a sensitivity of 2.6 x 10^-5 e/Hz^1/2.Comment: 5 pages, 5 figures, submitted to RS

Localization of a dipolar Bose-Einstein condensate in a bichromatic optical lattice

By numerical simulation and variational analysis of the Gross-Pitaevskii equation we study the localization, with an exponential tail, of a dipolar Bose-Einstein condensate (DBEC) of $^{52}$Cr atoms in a three-dimensional bichromatic optical-lattice (OL) generated by two monochromatic OL of incommensurate wavelengths along three orthogonal directions. For a fixed dipole-dipole interaction, a localized state of a small number of atoms ($\sim 1000$) could be obtained when the short-range interaction is not too attractive or not too repulsive. A phase diagram showing the region of stability of a DBEC with short-range interaction and dipole-dipole interaction is given

Anomalous Spin Dynamics of Hubbard Model on Honeycomb Lattices

In this paper, the honeycomb Hubbard model in optical lattices is investigated using O(3) non-linear sigma model. A possible quantum non-magnetic insulator in a narrow parameter region is found near the metal-insulator transition. We study the corresponding dynamics of magnetic properties, and find that the narrow region could be widened by hole doping.Comment: 9 pages, 12 figure

Superdeformed Band in ^{36}Ar Described by Projected Shell Model

The projected shell model implements shell model configuration mixing in the projected deformed basis. Our analysis on the recently observed superdeformed band in $^{36}$Ar suggests that the neutron and proton 2-quasiparticle and the 4-quasiparticle bands cross the superdeformed ground band at the same angular momentum. This constitutes a picture of band disturbance in which the first and the second band-crossing, commonly seen at separate rotation frequencies in heavy nuclei, occur simultaneously. We also attempt to understand the assumptions of two previous theoretical calculations which interpreted this band. Electromagnetic properties of the band are predicted.Comment: 4 pages and 2 figures, accepted by Phys. Rev. C as a Rapid Communicatio

Anomalous rotational-alignment in N=Z nuclei and residual neutron-proton interaction

Recent experiments have demonstrated that the rotational-alignment for the $N=Z$ nuclei in the mass-80 region is considerably delayed as compared to the neighboring $N \ne Z$ nuclei. We investigate whether this observation can be understood by a known component of nuclear residual interactions. It is shown that the quadrupole-pairing interaction, which explains many of the delays known in rare-earth nuclei, does not produce the substantial delay observed for these $N=Z$ nuclei. However, the residual neutron-proton interaction which is conjectured to be relevant for $N=Z$ nuclei is shown to be quite important in explaining the new experimental data.Comment: 4 pages, 3 figures, final version accepted by Phys. Rev. C as a Rapid Communicatio

Cascade of magnetic field induced Lifshitz transitions in the ferromagnetic Kondo lattice material YbNi4P2

A ferromagnetic quantum critical point is thought not to exist in two and three-dimensional metallic systems yet is realized in the Kondo lattice compound YbNi4(P,As)2, possibly due to its one-dimensionality. It is crucial to investigate the dimensionality of the Fermi surface of YbNi4P2 experimentally but common probes such as ARPES and quantum oscillation measurements are lacking. Here, we studied the magnetic field dependence of transport and thermodynamic properties of YbNi4P2. The Kondo effect is continuously suppressed and additionally we identify nine Lifshitz transitions between 0.4 and 18 T. We analyze the transport coefficients in detail and identify the type of Lifshitz transitions as neck or void type to gain information on the Fermi surface of YbNi4P2. The large number of Lifshitz transitions observed within this small energy window is unprecedented and results from the particular flat renormalized band structure with strong 4f-electron character shaped by the Kondo lattice effect.Comment: 6 pages, 4 figure

The f0(1370)f_0(1370), f0(1710)f_0(1710), f2(1270)f_2(1270), f2′(1525)f_2'(1525), and K2∗(1430)K_2^*(1430) as dynamically generated states from vector meson - vector meson interaction

We report on some recent developments in understanding the nature of the low-lying mesonic resonances $f_0(1370)$, $f_0(1710)$, $f_2(1270)$, $f_2'(1525)$, and $K_2^*(1430)$. In particular we show that these five resonances can be dynamically generated from vector meson--vector meson interaction in a coupled-channel unitary approach, which utilizes the phenomenologically very successful hidden-gauge Lagrangians to produce the interaction kernel between two vector mesons, which is then unitarized by the Bethe-Salpeter-equation method. The data on the strong decay branching ratios, total decay widths, and radiative decay widths of these five states, and on related $J/\psi$ decay processes can all be well described by such an approach. We also make predictions, compare them with the results of earlier studies, and highlight observables that if measured can be used to distinguish different pictures of these resonances.Comment: 9 pages; Invited talk at workshop CHIRAL'10, Valencia (Spain), June 21-24, 201