Quantum criticality in the two-channel pseudogap Anderson model: A test of the non-crossing approximation

We investigate the dynamical properties of the two-channel Anderson model using the noncrossing approximation (NCA) supplemented by numerical renormalization-group calculations. We provide evidence supporting the conventional wisdom that the NCA gives reliable results for the standard two-channel Anderson model of a magnetic impurity in a metal. We extend the analysis to the pseudogap two-channel model describing a semi-metallic host with a density of states that vanishes in power-law fashion at the Fermi energy. This model exhibits continuous quantum phase transitions between weak- and strong-coupling phases. The NCA is shown to reproduce the correct qualitative features of the pseudogap model, including the phase diagram, and to yield critical exponents in excellent agreement with the NRG and exact results. The forms of the dynamical magnetic susceptibility and impurity Green's function at the fixed points are suggestive of frequency-over-temperature scaling.Comment: 6 pages, 10 figures, to appear in the special issue of pss on Quantum Criticality and Novel Phases (QCNP12

Entanglement Entropy Near Kondo-Destruction Quantum Critical Points

We study the impurity entanglement entropy $S_e$ in quantum impurity models that feature a Kondo-destruction quantum critical point (QCP) arising from a pseudogap in the conduction-band density of states or from coupling to a bosonic bath. On the local-moment (Kondo-destroyed) side of the QCP, the entanglement entropy contains a critical component that can be related to the order parameter characterizing the quantum phase transition. In Kondo models describing a spin-\Simp, $S_e$ assumes its maximal value of \ln(2\Simp+1) at the QCP and throughout the Kondo phase, independent of features such as particle-hole symmetry and under- or over-screening. In Anderson models, $S_e$ is nonuniversal at the QCP, and at particle-hole symmetry, rises monotonically on passage from the local-moment phase to the Kondo phase; breaking this symmetry can lead to a cusp peak in $S_e$ due to a divergent charge susceptibility at the QCP. Implications of these results for quantum critical systems and quantum dots are discussed.Comment: 15 pages, 8 figures, replaced with published version, Editor's Suggestio

Competition between Kondo and Kitaev Physics in Kitaev clusters coupled to a fermionic bath

Geometrically frustrated quantum impurities coupled to metallic leads have been shown to exhibit rich behavior with a quantum phase transition separating Kondo screened and local moment phases. Frustration in the quantum impurity can alternatively be introduced via Kitaev-couplings between different spins of the impurity cluster. We use the Numerical Renormalization Group (NRG) to study a range of systems where the quantum impurity comprising a Kitaev cluster is coupled to a bath of non-interacting fermions. The models exhibits a competition between Kitaev and Kondo dominated physics depending on whether the Kitaev couplings are greater or less than the Kondo temperature. We characterize the ground state properties of the system and determine the temperature dependence of the crossover scale for the emergence of fractionalized degrees of freedom in the model. We also demonstrate qualitatively as well as quantitatively that in the Kondo limit, the complex impurity can be mapped to an effective two-impurity system, where the emergent spin $1/2$ comprises of both Majorana and flux degrees of freedom. For a tetrahedral-shaped Kitaev cluster, an extra orbital degree of freedom closely related to a flux degree of freedom remains unscreened even in the presence of both Heisenberg and Kondo interactions

Quantum criticality in the two-channel pseudogap Anderson model: A test of the non-crossing approximation

We investigate the dynamical properties of the twochannel Anderson model using the noncrossing approximation (NCA) supplemented by numerical renormalization-group calculations. We provide evidence supporting the conventional wisdom that the NCA gives reliable results for the standard two-channel Anderson model of a magnetic impurity in a metal. We extend the analysis to the pseudogap two-channel model describing a semi-metallic host with a density of states that vanishes in power-law fashion at the Fermi energy. This model exhibits continuous quantum phase transitions between weak-and strong-coupling phases. The NCA is shown to reproduce the correct qualitative features of the pseudogap model, including the phase diagram, and to yield critical exponents in excellent agreement with the NRG and exact results. The forms of the dynamical magnetic susceptibility and impurity Green's function at the fixed points are suggestive of frequencyover-temperature scaling. Copyright line will be provided by the publisher 1 Introduction Quantum criticality is currently pursued across many areas of correlated matter, from insulating or weak magnets to metal-insulator systems to unconventional superconductors. Interest in continuous phase transitions at temperature T = 0 is motivated both by the appearance of novel phases near such transitions and by a richness of quantum critical states that extends beyond the traditional description in terms of order-parameter fluctuations. A fertile area for experimental study has been the border of magnetism in rare-earth and actinide intermetallics, where there is mounting evidence that a crucial issue is the fate of the Kondo effect on approach to the quantum phase transitio

Local Inaccessibility of Random Classical Information : Conditional Nonlocality demands Entanglement

Discrimination of quantum states under local operations and classical communication (LOCC) is an intriguing question in the context of local retrieval of classical information, encoded in the multipartite quantum systems. All the local quantum state discrimination premises, considered so far, mimic a basic communication set-up, where the spatially separated decoding devices are independent of any additional input. Here, exploring a generalized communication scenario we introduce a framework for input-dependent local quantum state discrimination, which we call local random authentication (LRA). Referring to the term nonlocality, often used to indicate the impossibility of local state discrimination, we coin the term conditional nonlocality for the impossibility associated with the task LRA. We report that conditional nonlocality necessitates the presence of entangled states in the ensemble, a feature absent from erstwhile nonlocality arguments based on local state discrimination. Conversely, all the states in a complete basis set being entangled implies conditional nonlocality. However, the impossibility of LRA also exhibits more conditional nonlocality with less entanglement. The relation between the possibility of LRA and local state discrimination for sets of multipartite quantum states, both in the perfect and conclusive cases, has also been established. The results highlight a completely new aspect of the interplay between the security of information in a network and quantum entanglement under the LOCC paradigm.Comment: An appropriate example for Proposition 2 is added and the details of which is supplemented in the Appendi

Phase boundaries of power-law Anderson and Kondo models: A poor man's scaling study

We use the poor man's scaling approach to study the phase boundaries of a pair of quantum impurity models featuring a power-law density of states rho(epsilon) proportional to | epsilon| (r), either vanishing (for r > 0) or diverging (for r 0), we find the phase boundary for (a) 0 1, where the phases are separated by first-order quantum phase transitions that are accessible only for broken p-h symmetry. For the p-h-symmetric Kondo model with easy-axis or easy-plane anisotropy of the impurity-band spin exchange, the phase boundary and scaling trajectories are obtained for both r > 0 and r < 0. Throughout the regime of weak-to-moderate impurity-band coupling in which poor man's scaling is expected to be valid, the approach predicts phase boundaries in excellent qualitative and good quantitative agreement with the nonperturbative numerical renormalization group, while also establishing the functional relations between model parameters along these boundaries

Long-Range Entanglement near a Kondo-Destruction Quantum Critical Point

The numerical renormalization group is used to study quantum entanglement in the Kondo impurity model with a density of states rho(epsilon) proportional to vertical bar epsilon vertical bar(r) (0 > R* of weak entanglement. Within each phase, S-e(imp) is a universal function of R/R* with a power-law decay for R/R* >> 1. The entanglement length R* diverges on approach to the interacting QCP, showing that the critical Kondo screening cloud subsumes the entire system as the impurity becomes maximally entangled with the conduction band. This work has implications for entanglement calculations in other models and for the nature of heavy-fermion quantum criticality

Pharmacological applications of diacerein: A review

IL-1β is one of the important IL-1 superfamily cytokines that shows crucial role in the pathogenesis of various inflammatory disorders like osteoarthritis, epidermolysis bullosa, psoriasis and type II diabetes. Dugs with IL-1βinhibitory effect can show promising results in these types of inflammatory disorders. Diacerein and its active metabolite rhein prevent the generation of active IL-1 and are consequently used to treat inflammatory conditions such as osteoarthritis, epidermolysis bullosa, psoriasis, and Type II diabetes