Spin-orbit and impurity scattering in an integrable electron model: Exact results for dynamic correlations

We introduce an integrable model of spin-polarized interacting electrons subject to a spin-conserving spin-orbit interaction. Using Bethe Ansatz and conformal field theory we calculate the exact large-time single-electron and density correlations and find that while the spin-orbit interaction enhances the single-electron Green's function, the density correlations get suppressed. Adding a localized impurity and coupling it to the electrons so that integrability is preserved, the dynamic correlations are found to change significantly after a quantum quench with the impurity interaction switched on suddenly. When the electrons are confined to a periodic structure, the correlations are indifferent to the location of the impurity and only carry an imprint of its intrinsic properties. We conjecture that this unusual feature originates from the integrability of the model.Comment: 8 pages, 1 figur

Reproduction of the Lyman α irradiance variability from analysis of full-disk images in the CaII K-line

We have compared three years of daily CaII K-line images from the Big Bear Solar Observatory (BBSO) with HI Lymanα irradiance data from the Upper Atmosphere Research Satellite (UARS). The daily full-disk CaII K-line images are reduced to a new index of integrated excess emission, which reproduces both the 27 day rotational modulation and the solar cycle decrease in Lyα irradiance. Our analysis shows that while plages reproduce the 27-day variation quite well, the total K-line emission excess above the quiet background is needed to reproduce the secular solar cycle trend in the Lyα irradiance. The resulting K-line index exhibits a high degree of correlation (0.9) with the time series of measured Lyα flux

Addendum to ``Multichannel Kondo screening in a one-dimensional correlated electron system''

This is an addendum to our previous work cond-mat/9705048 (published in Europhysics Letters 41, 213 (1998)), clarifying the construction of the two-particle scattering matrices used for studying the magnetic impurity behavior in a multichannel correlated host.Comment: Addendum to cond-mat/9705048 (Europhys. Lett. 41, 213 (1998)

Extra Shared Entanglement Reduces Memory Demand in Quantum Convolutional Coding

We show how extra entanglement shared between sender and receiver reduces the memory requirements for a general entanglement-assisted quantum convolutional code. We construct quantum convolutional codes with good error-correcting properties by exploiting the error-correcting properties of an arbitrary basic set of Pauli generators. The main benefit of this particular construction is that there is no need to increase the frame size of the code when extra shared entanglement is available. Then there is no need to increase the memory requirements or circuit complexity of the code because the frame size of the code is directly related to these two code properties. Another benefit, similar to results of previous work in entanglement-assisted convolutional coding, is that we can import an arbitrary classical quaternary code for use as an entanglement-assisted quantum convolutional code. The rate and error-correcting properties of the imported classical code translate to the quantum code. We provide an example that illustrates how to import a classical quaternary code for use as an entanglement-assisted quantum convolutional code. We finally show how to "piggyback" classical information to make use of the extra shared entanglement in the code.Comment: 7 pages, 1 figure, accepted for publication in Physical Review

Tunneling between edge states in a quantum spin Hall system

We analyze a quantum spin Hall (QSH) device with a point contact connecting two of its edges. The contact supports a net spin tunneling current that can be probed experimentally via a two-terminal resistance measurement. We find that the low-bias tunneling current and the differential conductance exhibit scaling with voltage and temperature that depend nonlinearly on the strength of the electron-electron interaction.Comment: 4 pages, 3 figures; published versio

Entanglement probe of two-impurity Kondo physics in a spin chain

We propose that real-space properties of the two-impurity Kondo model can be obtained from an effective spin model where two single-impurity Kondo spin chains are joined via an RKKY interaction between the two impurity spins. We then use a DMRG approach, valid in all ranges of parameters, to study its features using two complementary quantum-entanglement measures, the negativity and the von Neumann entropy. This non-perturbative approach enables us to uncover the precise dependence of the spatial extent $\xi_K$ of the Kondo screening cloud with the Kondo and RKKY couplings. Our results reveal an exponential suppression of the Kondo temperature $T_K \sim 1/\xi_K$ with the size of the effective impurity spin in the limit of large ferromagnetic RKKY coupling, a striking display of "Kondo resonance narrowing" in the two-impurity Kondo model. We also show how the antiferromagnetic RKKY interaction produces an effective decoupling of the impurities from the bulk already for intermediate strengths of this interaction, and, furthermore, exhibit how the non-Fermi liquid quantum critical point is signaled in the quantum entanglement between various parts of the system.Comment: 5 pages, 5 figure