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Search Results: 1 - 10 of 297486 matches for " J. Mesot "
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Hot Spots on the Fermi Surface of Bi2212: Stripes versus Superstructure
J. Mesot,M. R. Norman,H. Ding,J. C. Campuzano
Physics , 1998, DOI: 10.1103/PhysRevLett.82.2618
Abstract: In a recent paper Saini et al. have reported evidence for a pseudogap around (pi,0) at room temperature in the optimally doped superconductor Bi2212. This result is in contradiction with previous ARPES measurements. Furthermore they observed at certain points on the Fermi surface hot spots of high spectral intensity which they relate to the existence of stripes in the CuO planes. They also claim to have identified a new electronic band along Gamma-M1 whose one dimensional character provides further evidence for stripes. We demonstrate in this Comment that all the measured features can be simply understood by correctly considering the superstructure (umklapp) and shadow bands which occur in Bi2212.
The Temperature Evolution of the Spectral Peak in High Temperature Superconductors
M. R. Norman,A. Kaminski,J. Mesot,J. C. Campuzano
Physics , 2000, DOI: 10.1103/PhysRevB.63.140508
Abstract: Recent photoemission data in the high temperature cuprate superconductor Bi2212 have been interpreted in terms of a sharp spectral peak with a temperature independent lifetime, whose weight strongly decreases upon heating. By a detailed analysis of the data, we are able to extract the temperature dependence of the electron self-energy, and demonstrate that this intepretation is misleading. Rather, the spectral peak loses its integrity above Tc due to a large reduction in the electron lifetime.
Doping dependence of the vortex glass and sublimation transitions in the high-$T_{c}$ superconductor La$_{2-x}$Sr$_{x}$CuO$_{4}$ as determined from macroscopic measurements
R. Gilardi,S. Streule,J. Mesot,N. Momono,M. Oda
Physics , 2004, DOI: 10.1140/epjb/e2005-00322-1
Abstract: Magnetization and ac-susceptibility measurements are used to characterize the mixed phase of the high-temperature cuprate superconductor La$_{2-x}$Sr$_{x}$CuO$_{4}$ over a large range of doping (0.075 $\leq x\leq$ 0.20). The first order vortex lattice phase transition line $H_{FOT}(T)$, the upper critical field $H_{c2}(T)$ and the second peak $H_{sp}(T)$ have been investigated up to high magnetic fields (8 Tesla applied perpendicular to the $CuO_2$ planes). Our results reveal a strong doping dependence of the magnetic phase diagram, which can mainly be explained by the increasing anisotropy with underdoping. Within our interpretation, the first order vortex lattice phase transition is due to the sublimation (rather than melting) of the vortex lattice into a gas of pancake vortices, whereas the second peak is related to the transition to a more disordered vortex glass state.
Incommensurate magnetic ordering in $Cu_2 Te_2 O_5 X_2$ (X=Cl,Br) studied by neutron diffraction
O. Zaharko,A. Daoud-Aladine,S. Streule,J. Mesot,P. -J. Brown,H. Berger
Physics , 2004, DOI: 10.1103/PhysRevLett.93.217206
Abstract: We present the results of the first neutron powder and single crystal diffraction studies of the coupled spin tetrahedra systems ${\CuTeX}$ (X=Cl, Br). Incommensurate antiferromagnetic order with the propagation vectors ${\bf{k}_{Cl}}\approx[0.150,0.422,\half]$, ${\bf{k}_{Br}}\approx[0.158,0.354,\half]$ sets in below $T_{N}$=18 K for X=Cl and 11 K for X=Br. No simple collinear antiferromagnetic or ferromagnetic arrangements of moments within Cu${}^{2+}$ tetrahedra fit these observations. Fitting the diffraction data to more complex but physically reasonable models with multiple helices leads to a moment of 0.67(1)$\mu_B$/Cu${}^{2+}$ at 1.5 K for the Cl-compound. The reason for such a complex ground state may be geometrical frustration of the spins due to the intra- and inter-tetrahedral couplings having similar strengths. The magnetic moment in the Br- compound, calculated assuming it has the same magnetic structure as the Cl compound, is only 0.51(5)$\mu_B$/Cu${}^{2+}$ at 1.5 K. In neither compound has any evidence for a structural transition accompanying the magnetic ordering been found.
Influence of higher d-wave gap harmonics on the dynamical magnetic susceptibility of high-temperature superconductors
A. P. Schnyder,A. Bill,C. Mudry,R. Gilardi,H. M. Ronnow,J. Mesot
Physics , 2004, DOI: 10.1103/PhysRevB.70.214511
Abstract: Using a fermiology approach to the computation of the magnetic susceptibility measured by neutron scattering in hole-doped high-Tc superconductors, we estimate the effects on the incommensurate peaks caused by higher d-wave harmonics of the superconducting order parameter induced by underdoping. The input parameters for the Fermi surface and d-wave gap are taken directly from angle resolved photoemission (ARPES) experiments on Bi{2}Sr{2}CaCu{2}O{8+x} (Bi2212). We find that higher d-wave harmonics lower the momentum dependent spin gap at the incommensurate peaks as measured by the lowest spectral edge of the imaginary part in the frequency dependence of the magnetic susceptibility of Bi2212. This effect is robust whenever the fermiology approach captures the physics of high-Tc superconductors. At energies above the resonance we observe diagonal incommensurate peaks. We show that the crossover from parallel incommensuration below the resonance energy to diagonal incommensuration above it is connected to the values and the degeneracies of the minima of the 2-particle energy continuum.
Direct observation of impurity-induced magnetism in an S = 1/2 antiferromagnetic Heisenberg 2-leg spin ladder
F. Casola,T. Shiroka,S. Wang,K. Conder,E. Pomjakushina,J. Mesot,H. -R. Ott
Physics , 2010, DOI: 10.1103/PhysRevLett.105.067203
Abstract: Nuclear magnetic resonance and magnetization measurements were used to probe the magnetic features of single-crystalline Bi(Cu(1-x)Znx)2PO6 with 00 and we present clear evidence for a temperature dependent variation of the local magnetization close to the Zn sites. The generic nature of this observation is indicated by results of model calculations on appropriate spin systems of limited size employing QMC methods.
Unusual interplay between copper-spin and vortex dynamics in slightly overdoped La{1.83}Sr{0.17}CuO{4}
R. Gilardi,A. Hiess,N. Momono,M. Oda,M. Ido,J. Mesot
Physics , 2003, DOI: 10.1209/epl/i2003-10265-1
Abstract: Our inelastic neutron scattering experiments of the spin excitations in the slightly overdoped La{1.83}Sr{0.17}CuO{4} compound show that, under the application of a magnetic field of 5 Tesla, the low-temperature susceptibility undergoes a weight redistribution centered at the spin-gap energy. Furthermore, by comparing the temperature dependence of the neutron data with ac-susceptibility and magnetization measurements, we conclude that the filling in of the spin gap tracks the irreversibility/melting temperature rather than Tc2, which indicates an unusual interplay between the magnetic vortices and the spin excitations even in the slightly overdoped regime of high-temperature superconductors.
Pairing of weakly correlated electrons in the platinum-based centrosymmetric superconductor SrPt3P
T. Shiroka,M. Pikulski,N. D. Zhigadlo,B. Batlogg,J. Mesot,H. -R. Ott
Physics , 2015, DOI: 10.1103/PhysRevB.91.245143
Abstract: We report a study of the normal- and superconducting-state electronic properties of the centrosymmetric compound SrPt3P via 31P nuclear-magnetic-resonance (NMR) and magnetometry investigations. Essential features such as a sharp drop of the Knight shift at T < Tc and an exponential decrease of the NMR spin-lattice relaxation ratio 1/(T1T) below Tc are consistent with an s-wave electron pairing in SrPt3P, although a direct confirmation in the form of a Hebel-Slichter-type peak is lacking. Normal-state NMR data at T < 50 K indicate conventional features of the conduction electrons, typical of simple metals such as lithium or silver. Our data are finally compared with available NMR results for the noncentrosymmetric superconductors LaPt$_3$Si and CePt$_3$Si, which adopt similar crystal structures.
Distribution of NMR relaxations in a random Heisenberg chain
T. Shiroka,F. Casola,V. Glazkov,A. Zheludev,K. Prsa,H. -R. Ott,J. Mesot
Physics , 2010, DOI: 10.1103/PhysRevLett.106.137202
Abstract: Nuclear magnetic resonance (NMR) measurements of the 29Si spin-lattice relaxation time T1 were used to probe the spin-1/2 random Heisenberg chain compound BaCu2(Si(1-x)Gex)2O7. Remarkable differences between the pure (x = 0) and the fully random (x = 0.5) case are observed, indicating that randomness generates a distribution of local magnetic relaxations. This distribution, which is reflected in a stretched exponential NMR relaxation, exhibits a progressive broadening with decreasing temperature, caused by a growing inequivalence of magnetic sites. Compelling independent evidence for the influence of randomness is also obtained from magnetization data and Monte Carlo calculations. These results suggest the formation of random-singlet states in this class of materials, as previously predicted by theory.
Impact of strong disorder on the static magnetic properties of the spin-chain compound BaCu2SiGeO7
T. Shiroka,F. Casola,W. Lorenz,A. Zheludev,H. -R. Ott,J. Mesot
Physics , 2013, DOI: 10.1103/PhysRevB.88.054422
Abstract: The disordered quasi-1D magnet BaCu2SiGeO7 is considered as one of the best physical realizations of the random Heisenberg chain model, which features an irregular distribution of the exchange parameters and whose ground state is predicted to be the scarcely investigated random-singlet state (RSS). Based on extensive 29Si NMR and magnetization studies of BaCu2SiGeO7, combined with numerical Quantum Monte Carlo simulations, we obtain remarkable quantitative agreement with theoretical predictions of the random Heisenberg chain model and strong indications for the formation of a random-singlet state at low temperatures in this compound. As a local probe, NMR is a well-adapted technique for studying the magnetism of disordered systems. In this case it also reveals an additional local transverse staggered field (LTSF), which affects the low-temperature properties of the RSS. The proposed model Hamiltonian satisfactorily accounts for the temperature dependence of the NMR line shapes.
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