Charge Independence and Charge Symmetry

Charge independence and charge symmetry are approximate symmetries of nature, violated by the perturbing effects of the mass difference between up and down quarks and by electromagnetic interactions. The observations of the symmetry breaking effects in nuclear and particle physics and the implications of those effects are reviewed.Comment: 41 pages, report # DOE/ER/40427-17-N94, Chapter for a book titled "Symmetries and Fundamental Interactions in Nuclei" eds. E.M. Henley and W. Haxton, to be published by World Scientifi

Surface Screening Charge and Effective Charge

The charge on an atom at a metallic surface in an electric field is defined as the field-derivative of the force on the atom, and this is consistent with definitions of effective charge and screening charge. This charge can be found from the shift in the potential outside the surface when the atoms are moved. This is used to study forces and screening on surface atoms of Ag(001) c$(2\times 2)$ -- Xe as a function of external field. It is found that at low positive (outward) fields, the Xe with a negative effective charge of -0.093 $|{e}|$ is pushed into the surface. At a field of 2.3 V \AA$^{-1}$ the charge changes sign, and for fields greater than 4.1 V \AA$^{-1}$ the Xe experiences an outward force. Field desorption and the Eigler switch are discussed in terms of these results.Comment: 4 pages, 1 figure, RevTex (accepted by PRL

Charge Order in a Two-Dimensional Kondo Lattice Model

The possibility of charge order is theoretically examined for the Kondo lattice model in two dimensions, which does not include bare repulsive interactions. Using two complementary numerical methods, we find that charge order appears at quarter filling in an intermediate Kondo coupling region. The charge ordered ground state is an insulator exhibiting an antiferromagnetic order at charge-poor sites, while the paramagnetic charge-ordered state at finite temperatures is metallic with pseudogap behavior. We confirm that the stability of charge order is closely related with the local Kondo-singlet formation at charge-rich sites. Our results settle the controversy on charge order in the Kondo lattice model in realistic spatial dimensions.Comment: 5 pages, 4 figure

Measuring Charge Transport in an Amorphous Semiconductor Using Charge Sensing

We measure charge transport in hydrogenated amorphous silicon (a-Si:H) using a nanometer scale silicon MOSFET as a charge sensor. This charge detection technique makes possible the measurement of extremely large resistances. At high temperatures, where the a-Si:H resistance is not too large, the charge detection measurement agrees with a direct measurement of current. The device geometry allows us to probe both the field effect and dispersive transport in the a-Si:H using charge sensing and to extract the density of states near the Fermi energy.Comment: 4 pages, 4 figure

Mesoscopic Charge Relaxation

We consider charge relaxation in the mesoscopic equivalent of an RC circuit. For a single-channel, spin-polarized contact, self-consistent scattering theory predicts a universal charge relaxation resistance equal to half a resistance quantum independent of the transmission properties of the contact. This prediction is in good agreement with recent experimental results. We use a tunneling Hamiltonian formalism and show in Hartree-Fock approximation, that at zero temperature the charge relaxation resistance is universal even in the presence of Coulomb blockade effects. We explore departures from universality as a function of temperature and magnetic field.Comment: 4 pages, 3 figure

Charge Fluctuations of a Schwarzschild Black-Hole

In this paper we calculate charge fluctuations of a Schwarzschild black-hole of mass $M$ in thermal equilibrium with radiation and an electron-positron plasma confined within a vessel of radius R. We show that charge fluctuations are always present, even if the black-hole is neutral and the overall charge of the system vanishes. Furthermore, if $R/M >>1$ the system becomes unstable under charge fluctuations. Surprisingly enough, besides the expected thermodynamical black hole charge fluctuation that result from the fluctuations on the number of charge carriers, there are other contributions to the overall charge fluctuation of the black-hole which, against our intuition, do not depend upon the charge of the particles. We conjecture that one of the contributions is an intrinsic purely quantum mechanical fluctuation of the black-hole itself as it does not depend on any of the control parameters, namely the radius of the confining cavity nor the temperature of the system, and even not upon the mass or charge of the particles

Cu nuclear magnetic resonance study of charge and spin stripe order in La1.875_{1.875}Ba0.125_{0.125}CuO4_4

We present a Cu nuclear magnetic/quadrupole resonance study of the charge stripe ordered phase of LBCO, with detection of previously unobserved ('wiped-out') signal. We show that spin-spin and spin-lattice relaxation rates are strongly enhanced in the charge ordered phase, explaining the apparent signal decrease in earlier investigations. The enhancement is caused by magnetic, rather than charge fluctuations, conclusively confirming the long-suspected assumption that spin fluctuations are responsible for the wipeout effect. Observation of the full Cu signal enables insight into the spin and charge dynamics of the stripe-ordered phase, and measurements in external magnetic fields provide information on the nature and suppression of spin fluctuations associated with charge order. We find glassy spin dynamics, in agreement with previous work, and incommensurate static charge order with charge modulation amplitude similar to other cuprate compounds, suggesting that the amplitude of charge stripes is universal in the cuprates.Comment: 7 pages, 5 figure