Collapse Of The G D3+ Esr Fine Structure Throughout The Coherent Temperature Of The Gd-doped Kondo Semiconductor Cef E4 P12

Recent experiments on Gd3+ electron-spin resonance (ESR) in the filled skutterudite Ce1-xGdxFe4P12(x≈0.001), at temperatures where the host resistivity manifests a smooth insulator-metal crossover, provide evidence of the underlying Kondo physics associated with this system. At low temperatures (below T≈160 K), Ce1-xGdxFe4P12 behaves as a Kondo insulator with a relatively large hybridization gap, and the Gd3+ ESR spectra display a fine structure with Lorentzian line shape, typical of insulating media. In this work, based on previous experiments performed by the same group, we argue that the electronic gap may be attributed to the large hybridization present in the coherent regime of a Kondo lattice. Moreover, mean-field calculations suggest that the electron-phonon interaction is fundamental at explaining such hybridization. The resulting electronic structure is strongly temperature dependent, and at T∗≈160K the system undergoes an insulator-to-metal transition induced by the withdrawal of 4f electrons from the Fermi volume, the system becoming metallic and nonmagnetic. The Gd3+ ESR fine structure coalesces into a single Dysonian resonance, as in metals. Our simulations suggest that exchange narrowing via the usual Korringa mechanism is not enough to describe the thermal behavior of the Gd3+ ESR spectra in the entire temperature region (4.2-300 K). We propose that the temperature activated fluctuating valence of the Ce ions is the key ingredient that fully describes this unique temperature dependence of the Gd3+ ESR fine structure. © 2016 American Physical Society.942

Mesoscopic superconductors in the London limit: equilibrium properties and metastability

We present a study of the behaviour of metastable vortex states in mesoscopic superconductors. Our analysis relies on the London limit within which it is possible to derive closed analytical expressions for the magnetic field and the Gibbs free energy. We consider in particular the situation where the vortices are symmetrically distributed along a closed ring. There, we obtain expressions for the confining Bean-Livingston barrier and for the magnetization which turns out to be paramagnetic away from thermodynamic equilibrium. At low temperature, the barrier is high enough for this regime to be observable. We propose also a local description of both thermodynamic and metastable states based on elementary topological considerations; we find structural phase transitions of vortex patterns between these metastable states and we calculate the corresponding critical fields.Comment: 24 pages, 20 figure

A dual point description of mesoscopic superconductors

We present an analysis of the magnetic response of a mesoscopic superconductor, i.e. a system of sizes comparable to the coherence length and to the London penetration depth. Our approach is based on special properties of the two dimensional Ginzburg-Landau equations, satisfied at the dual point $(\kappa = \frac{1}{\sqrt{2}}).$ Closed expressions for the free energy and the magnetization of the superconductor are derived. A perturbative analysis in the vicinity of the dual point allows us to take into account vortex interactions, using a new scaling result for the free energy. In order to characterize the vortex/current interactions, we study vortex configurations that are out of thermodynamical equilibrium. Our predictions agree with the results of recent experiments performed on mesoscopic aluminium disks.Comment: revtex, 20 pages, 9 figure

Quantum walks: a comprehensive review

Quantum walks, the quantum mechanical counterpart of classical random walks, is an advanced tool for building quantum algorithms that has been recently shown to constitute a universal model of quantum computation. Quantum walks is now a solid field of research of quantum computation full of exciting open problems for physicists, computer scientists, mathematicians and engineers. In this paper we review theoretical advances on the foundations of both discrete- and continuous-time quantum walks, together with the role that randomness plays in quantum walks, the connections between the mathematical models of coined discrete quantum walks and continuous quantum walks, the quantumness of quantum walks, a summary of papers published on discrete quantum walks and entanglement as well as a succinct review of experimental proposals and realizations of discrete-time quantum walks. Furthermore, we have reviewed several algorithms based on both discrete- and continuous-time quantum walks as well as a most important result: the computational universality of both continuous- and discrete- time quantum walks.Comment: Paper accepted for publication in Quantum Information Processing Journa

Nomenclatural instability in the venomous snakes of the Bothrops complex: Implications in toxinology and public health

We are deeply grateful to Wolfgang Wüster for his kind help and suggestions that enriched the manuscript, and to José María Gutiérrez and Gerardo Leynaud for their interest and useful comments on this work. We appreciate the constructive comments and suggestions of two anonymous reviewers. We thank Helena Shobe and Nicole Washburn for improvements in the English version of the manuscript, and Eugenia Lascano for helping with the figures edition. This work was supported by the Programa de Cooperación Científico-Tecnológica entre el Consejo Nacional de Ciencia, Tecnología e Innovación Tecnológica de Perú (CONCYTEC-FONDECYT CS-031-2014) y el Ministerio de Ciencia, Tecnología e Innovación Productiva de Argentina (MINCYT PE/13/06).Fondo Nacional de Desarrollo Científico y Tecnológico - Fondecy

Surface effects on the dynamic behavior of vortices in Type II superconducting strips with periodic and conformal pinning arrays

Using molecular dynamics techniques, we simulate the vortex behavior in a type II superconducting strip in the presence of triangular and two types of conformal pinning arrays, one with a pinning gradient perpendicular to the driving force (C1) and the other parallel (C2), at zero temperature. A transport force is applied in the infinite direction of the strip, and the magnetic field is increased until the rate between the density of vortices (nv) and pinning (np) reaches nv/np = 1.5. Our results show a monotonic increase, by steps, of the vortex density with the applied magnetic field. Besides, each pinning lattice presents a different vortex penetration delay. For the triangular pinning array, different than the case of infinite films, here the system exhibits only one pronounced depinning force peak at nv/np = 1. However, the depinning force peak is present for only one value of field, in the range of fields where nv/np = 1 is stable. For the case of conformal pinning arrays, in analogy to what is observed in infinite films, no commensurability depinning force peaks were found. In the present case, the C1 array is more efficient at low fields, all arrays are equivalent in the intermediate fields, and the C2 array is more efficient for high fields. We also show that for the C1 array at high fields, vortices depin following the conformal arches, from the edge to the center. For the C2 array, the depinning force is higher when compared to that of C1, because this particular conformal structure prevents the formation of easy vortex flow channels

Electron Spin Resonance Of Gd3 + In The Antiferromagnetic Heavy Fermion Cein3 And Its Reference Compound Lain3

We report temperature dependent electron spin resonance (ESR) experiments of Gd3 + in CeIn3 and in its reference compound LaIn3 taken in crushed single crystals. For LaIn3 a single Dysonian Gd3 + ESR line with a nearly temperature independent g ~ 2.020 (5) is observed, and its linewidth follows a Korringa-like behavior as a function of temperature. From the Korringa rate (Δ H / Δ T ~ 16 Oe / K) and g-shift (Δ g ~ 0.027) we have extracted the exchange parameter between the Gd3 + local moments and the conduction electrons (ce) in this compound. This exchange parameter Jfs ≈ 20 meV was found to be ce wave-vector independent. For CeIn3, the Gd3 + ESR spectra were found to be weakly temperature dependent and present partly resolved Gd3 + fine-structure. Interestingly, for CeIn3, the g-shift with respect to the g-value of Gd3 + in insulators is negative, in contrast to the positive g-shift found for Gd3 + in LaIn3. These results suggests different electronic structure at the Gd3 + site in the Kondo antiferromagnet host CeIn3. Possibly, Kondo effect may cause a decrease of the s-like conduction electron density of states at the Gd3 + site, giving arise to an exchange interaction only between the Gd3 + local moment and the Ce 4f electrons. © 2009 Elsevier B.V. All rights reserved.4041929952998Lawrence, J.M., (1979) Phys. Rev. B, 20, p. 3770Nasu, S., van Diepen, A.M., Newman, H.H., Craig, R.S., (1971) J. Phys. Chem. Solids, 32, p. 2773Kurosawa, Y., Umehara, I., Kikuchi, M., Nagai, N., Satoh, K., Onuki, Y., (1990) J. Phys. Soc. Japan, 5, p. 1545Lawrence, J.M., Shapiro, S.M., (1980) Phys. Rev. B, 22, p. 4379Mathur, N.D., Grosche, F.M., Julian, S.R., Walker, I.R., Freye, D.M., Haselwimmer, R.K.W., Lonzarich, G.G., (1998) Nature, 394, p. 39Thompson, J.D., (2001) J. Magn. Magn. Mater., 226-230, p. 5Pagliuso, P.G., (2002) Phys. B, 312-313, p. 129Welsh, L.B., Gambino, R.J., Toxen, A.M., (1971) J. Appl. Phys., 42, p. 1545Rettori, C., Oseroff, S.B., Rao, D., Pagliuso, P.G., Barberis, G.E., Sarrao, J., Fisk, Z., Hundley, M., (1997) Phys. Rev. B, 55, p. 1016Pires, M.A., Mendonça Ferreira, L., Duque, J.G.S., Urbano, R.R., Agüero, O., Torriani, I., Rettori, C., Pagliuso, P.G., (2006) J. Appl. Phys., 99, pp. 08J311Canfield, P.C., Fisk, Z., (1992) Philos. Mag. B, 65, p. 1117Pagliuso, P.G., (2002) Phys. Rev. B, 66, p. 054433Duque, J.G.S., (2007) Phys. Rev. B, 76, p. 125114. , and references thereinFeher, G., Kip, A.F., (1955) Phys. Rev., 98, p. 337Dyson, F.J., (1955) Phys. Rev., 98, p. 349Pake, G.E., Purcell, E.M., (1948) Phys. Rev., 74, p. 1184Yosida, K., (1957) Phys. Rev., 106, p. 893Korringa, J., (1950) Physica, 16, p. 601Davidov, D., Maki, K., Orbach, R., Rettori, C., Chock, E.P., (1973) Solid State Comm., 12, p. 621Davidov, D., Orbach, R., Rettori, C., Shaltiel, D., Tao, L.J., Ricks, B., (1971) Phys. Lett., 35 A, p. 339Rettori, C., Kim, H.M., Chock, E.P., Davidov, D., (1974) Phys. Rev. B, 10, p. 1826Abragam, A., Bleaney, B., (1970) EPR of Transition Ions, , Clarendon Press, Oxford p. 335Moriya, T., (1963) J. Phys. Soc. Japan, 18, p. 516Narath, A., (1967) Phys. Rev., 163, p. 232Urbano, R.R., (2007) Phys. Rev. B, 75, p. 045107Pagliuso, P.G., Rettori, C., Oseroff, S.B., Canfield, P.C., Baggio-Saitovitch, E.M., Sanchez, D., (1998) Phys. Rev. B, 57, p. 3668Pinto, J.W.M., Frota, H.O., (2001) Phys. Rev. B, 64, p. 092404Pagliuso, P.G., Rettori, C., Sarrao, J.L., Cornelius, A., Hundley, M.F., Fisk, Z., Oseroff, S.B., (1999) Phys. Rev. B, 60, p. 1351

Surface Effects On Vortex Dynamics In Thin Type-ii Superconducting Stripes With Random Pinning

We analyze the dynamics of a driven vortex lattice moving in a thin superconducting stripe. The two dimensional stripe is assumed to be finite in the longitudinal direction, where we take into account the surface effects, and infinite in the transversal direction. The numerical simulations are performed using the Langevin dynamics, including the vortex-vortex interaction, interaction of vortices with the surface current, vortex images, transport current and randomly distributed pinning centers. We show results for the differential resistivity and the vortex trajectories as a function of the external force. © 2004 Elsevier B.V. All rights reserved.408-4101-4595596Bhattacharya, S., (1993) Phys. Rev. Lett., 70, p. 2617Bhattacharya, S., (1995) Phys. Rev. B, 52, p. 64Maeda, A., (2002) Physica C, 369, p. 177Nori, F., (1996) Science, 271, p. 1373Carneiro, G., (1998) Phys. Rev. B, 57, p. 6077Kolton, A.B., (1999) Phys. Rev. Lett., 83, p. 3061Kolton, A.B., (2000) Phys. Rev. B, 62, p. 1465