Coherence and clock shifts in ultracold Fermi gases with resonant interactions

Using arguments based on sum rules, we derive a general result for the average shifts of rf lines in Fermi gases in terms of interatomic interaction strengths and two-particle correlation functions. We show that near an interaction resonance shifts vary inversely with the atomic scattering length, rather than linearly as in dilute gases, thus accounting for the experimental observation that clock shifts remain finite at Feshbach resonances.Comment: 4 pages, 2 figures. Nordita preprint NORDITA-2007-2

Observation of ferromagnetic resonance in strontium ruthenate (SrRuO3)

We report the observation of ferromagnetic resonance (FMR) in SrRuO3 using the time-resolved magneto-optical Kerr effect. The FMR oscillations in the time-domain appear in response to a sudden, optically induced change in the direction of easy-axis anistropy. The high FMR frequency, 250 GHz, and large Gilbert damping parameter, alpha ~ 1, are consistent with strong spin-orbit coupling. We find that the parameters associated with the magnetization dynamics, including alpha, have a non-monotonic temperature dependence, suggestive of a link to the anomalous Hall effect.Comment: submitted to Phys. Rev. Let

Subharmonic Gap Structure in Superconductor/Ferromagnet/Superconductor Junctions

The behavior of dc subgap current in magnetic quantum point contact is discussed for the case of low-transparency junction with different tunnel probabilities for spin-up ($D_\uparrow$) and spin-down ($D_\downarrow$) electrons. Due to the presence of Andreev bound states $\pm \epsilon_0$ in the system the positions of subgap electric current steps $eV_n = (\Delta \pm \epsilon_0)/n$ are split at temperature $T \neq 0$ with respect to the nonmagnetic result $eV_n=2\Delta/n$. It is found that under the condition $D_\uparrow \neq D_\downarrow$ the spin current also manifests subgap structure, but only for odd values of $n$. The split steps corresponding to $n=1,2$ in subgap electric and spin currents are analytically calculated and the following steps are described qualitatively.Comment: 4 pages, 1 figure, minor stylistic changes, journal-ref adde

Pushing the Limits for Judgmental Consistency: Comparing Random Weighting Schemes with Expert Judgments

Consistent use of information has been identified as a critical issue that can undermine expert predictions. Using three personnel assessment datasets, we conduct Monte Carlo simulations to compare the accuracy of expert judgements for predicting the job performance of managers against four different weighting schemes: consistent random weights, completely random weights, unit weights, and optimal weights. Expert accuracy fell within the completely random weight distribution in two samples and at the low end of the consistent random weight distribution in one sample. In other words, consistent random weights reliably outperformed expert judgment for hiring decisions across three datasets with a total sample size of 847. We see this as a call to develop decision making systems that help control consistency or to manage consistency by aggregating multiple expert judgments

Localized ferromagnetic resonance force microscopy in permalloy-cobalt films

We report Ferromagnetic Resonance Force Microscopy (FMRFM) experiments on a justaposed continuous films of permalloy and cobalt. Our studies demonstrate the capability of FMRFM to perform local spectroscopy of different ferromagnetic materials. Theoretical analysis of the uniform resonance mode near the edge of the film agrees quantitatively with experimental data. Our experiments demonstrate the micron scale lateral resolution in determining local magnetic properties in continuous ferromagnetic samples.Comment: 7 pages, 3 figure

Optical Generation and Quantitative Characterizations of Electron-hole Entanglement

Using a method of characterizing entanglement in the framework of quantum field theory, we investigate the optical generation and quantitative characterizations of quantum entanglement in an electron-hole system, in presence of spin-orbit coupling, and especially make a theoretical analysis of a recent experimental result. Basically, such entanglement should be considered as between occupation numbers of single particle basis states, and is essentially generated by coupling between different single particle basis states in the second quantized Hamiltonian. Interaction with two resonant light modes of different circular polarizations generically leads to a superposition of ground state and two heavy-hole excitonic states. When and only when the state is a superposition of only the two excitonic eigenstates, the entanglement reduces to that between two distinguishable particles, each with two degrees of freedom, namely, band index, as characterized by angular momentum, and orbit, as characterized by position or momentum. The band-index state, obtained by tracing over the orbital degree of freedom, is found to be a pure state, hence the band-index and orbital degrees of freedom are separated in this state. We propose some basic ideas on spatially separating the electron and the hole, so that the entanglement of band-indices, or angular momenta, is between spatially separated electron and hole.Comment: 8 pages. Journal versio

Hanbury-Brown-Twiss correlations and noise in the charge transfer statistics through a multiterminal Kondo dot

We analyze the full counting statistics of charge transfer through a quantum dot in the Kondo regime, when coupled to an arbitrary number of terminals N. At the unitary Kondo fixed point and for N>2 we recover distinct anticorrelations of currents in concurring transport channels, which are related to the fermionic Hanbury Brown and Twiss (HBT) antibunching. This effect weakens as one moves away from the fixed point. Furthermore, we identify a special class of current correlations that are due entirely to the virtual polarization of the Kondo singlet. These can be used for extracting information on the parameters of the underlying Fermi-liquid model.Comment: 5 page