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Articles 1 - 17 of 17
Full-Text Articles in Quantum Physics
Equivalent Dynamical Complexity In A Many-Body Quantum And Collective Human System, Neil F. Johnson, Josef Ashkenazi, Zhenyuan Zhao, Luis Quiroga
Equivalent Dynamical Complexity In A Many-Body Quantum And Collective Human System, Neil F. Johnson, Josef Ashkenazi, Zhenyuan Zhao, Luis Quiroga
Physics Articles and Papers
Proponents of Complexity Science believe that the huge variety of emergent phenomena observed throughout nature, are generated by relatively few microscopic mechanisms. Skeptics however point to the lack of concrete examples in which a single mechanistic model manages to capture relevant macroscopic and microscopic properties for two or more distinct systems operating across radically different length and time scales. Here we show how a single complexity model built around cluster coalescence and fragmentation, can cross the fundamental divide between many-body quantum physics and social science. It simultaneously (i) explains a mysterious recent finding of Fratini et al. concerning quantum many-body …
Scattering Of Scalar Light Fields From Collections Of Particles, Serkan Sahin, Olga Korotkova
Scattering Of Scalar Light Fields From Collections Of Particles, Serkan Sahin, Olga Korotkova
Physics Articles and Papers
Using the angular spectrum representation of fields and the first Born approximation we develop a theory of scattering of scalar waves with any spectral composition and any correlation properties from collections of particles which have either deterministic or random distributions of the index of refraction and locations. An example illustrating the far-field intensity and the far-field spectral degree of coherence produced on scattering of a model field from collections of several particles with Gaussian potentials is considered.
Intermediate Spin, Schrödinger Cat States, And Nanomagnets, S. E. Barnes
Intermediate Spin, Schrödinger Cat States, And Nanomagnets, S. E. Barnes
Physics Articles and Papers
Quantum tunneling in nanomagnets finds a natural description in terms of intermediate spin. Periodic magnetic effects correspond to a change of flux by the flux quantum Φ0. Schrödinger cat states with different superpositions of the applied magnetic field occur. The molecular magnet Fe8 is discussed and new effects are predicted for Mn12.
Paramagnetic Resonance Of Cu2+ Ions In The Superconductor Y0.2Ba0.8CuoX, F. Mehran, S. E. Barnes, T. R. Mcguire, W. J. Gallagher, R. L. Sandstrom, T. R. Dinger, D. A. Chance
Paramagnetic Resonance Of Cu2+ Ions In The Superconductor Y0.2Ba0.8CuoX, F. Mehran, S. E. Barnes, T. R. Mcguire, W. J. Gallagher, R. L. Sandstrom, T. R. Dinger, D. A. Chance
Physics Articles and Papers
A strong paramagnetic resonance signal characteristic of Cu2+ ions in ‖x2-y2〉 states is observed in the high-Tc≊90 K superconductor Y0.2Ba0.8CuOx. The line intensity of the ioniclike signal shows a deviation from Curie behavior at T≳Tc. It is speculated that the phase that is responsible for the signal is an example of an Anderson lattice with an unusually high Kondo temperature.
Theory Of In Situ Measurement Of Wave-Vector-Dependent Dynamic Susceptibility And Esr Spectroscopy Using The Ac Josephson Effect, S. E. Barnes, F. Mehran
Theory Of In Situ Measurement Of Wave-Vector-Dependent Dynamic Susceptibility And Esr Spectroscopy Using The Ac Josephson Effect, S. E. Barnes, F. Mehran
Physics Articles and Papers
The elementary theory of in situ measurements of the wave-vector-dependent dynamic susceptibility χ(q,ω) in superconductor-insulator-superconductor (SIS) and superconductor–normal-metal–superconductor (SNS) Josephson junctions is presented in some detail. The theory for more complicated SISN and SINS junctions is also described. In addition, the theory of point-contact and superconducting quantum interference device geometries, relevant to the recent experiments of Baberschke, Bures, and Barnes is developed. Involved is a detailed application of the Maxwell and London equations along with the distributed Josephson effect. In a measurement of χ(q,ω), the frequency ω is determined by the relation 2eV0=ħω where V0 is the …
Derivation Of Exact Results For The Single-Ion Kondo Problem With The Use Of Diagrammatic Methods, S. E. Barnes
Derivation Of Exact Results For The Single-Ion Kondo Problem With The Use Of Diagrammatic Methods, S. E. Barnes
Physics Articles and Papers
It is shown that exact results for the single-impurity Kondo problem can be obtained by diagrammatic methods. The results for the susceptibility and specific heat agree with those obtained by Wilson’s numerical methods. In particular, the crossover W’=(π/e)1/2 and Wilson R=2 ratios are reproduced exactly. Conduction-electron scattering from the impurity reaches the unitarity limit corresponding to a phase shift δ=π/2. Both this and the compensation of the impurity spin are also exact results. The methods described are relatively easily extended to the Anderson model and the corresponding lattice problems.
Solution Of The Kondo Problem By Diagrammatic Methods, S. E. Barnes
Solution Of The Kondo Problem By Diagrammatic Methods, S. E. Barnes
Physics Articles and Papers
A self-consistent parquet approximation is shown to give exact results for the Kondo problem in the scaling limit.
Esr And Magnetization Of The Spin-Glass Cumn At Low Concentrations, F. R. Hoekstra, G. J. Nieuwenhuys, K. Baberschke, S. E. Barnes
Esr And Magnetization Of The Spin-Glass Cumn At Low Concentrations, F. R. Hoekstra, G. J. Nieuwenhuys, K. Baberschke, S. E. Barnes
Physics Articles and Papers
We have determined the resonance frequency ω versus resonant field H diagram for CuMn with Mn concentrations 2, 3.5, and 5 at.%, both when H⃗ is parallel and antiparallel to the cooling field H⃗c. From the parallel measurements we find anisotropy energy density constants K that are in agreement with K values determined from transverse susceptibility and torque measurements. However, the K values determined from the remanence reversal of dc magnetization are smaller by a factor of approximately 2. We suggest that this is caused by a breakdown of rigid-body spin rotations. By combining the parallel data with …
Esr In Situ With A Josephson Tunnel Junction, K. Baberschke, K. D. Bures, S. E. Barnes
Esr In Situ With A Josephson Tunnel Junction, K. Baberschke, K. D. Bures, S. E. Barnes
Physics Articles and Papers
The in situ electron-spin resonance of a voltage-biased NbAuNb Josephson junction is reported. The Au barrier is doped with Gd or 167Er ions. Sharp resonances appear in the I-V curves at frequencies equivalent to the crystal-field splitting of AuGd (1.0 and 1.7 GHz) and to the hyperfine splitting of Au167Er (2.87 GHz). The principle of this new type of ESR-Josephson-junction spectrometer, as well as its application, is discussed.
Esr Relaxation In Spin Glasses, S. E. Barnes
Esr Relaxation In Spin Glasses, S. E. Barnes
Physics Articles and Papers
The Bloch-Hasegawa theory for the ESR of magnetic alloys is adapted and extended to spin glasses in the paramagnetic regime, that is, for temperatures T>TG, the cusp temperature. Negative residual widths, reduced thermal broadening, and a possible critical divergence of the residual width are all explained in terms of minor extensions of the standard theory.
Scaling Approach To Spin-Glass Phenomena, S. E. Barnes, A. P. Malozemoff, B. Barbara
Scaling Approach To Spin-Glass Phenomena, S. E. Barnes, A. P. Malozemoff, B. Barbara
Physics Articles and Papers
The scaling model of spin-glass phenomena is extended to consider both longitudinal and transverse order parameters q1 and qt. The lowest-order coupling in the free energy goes as ql2qt2. The field (h) dependence of the reduced temperature t for transverse freezing is found to be t∼h4/δ where δ is the conventional nonlinear susceptibility field exponent (χ∼h2/δ). While the transverse correlation length diverges at t=0, the longitudinal correlation length remains finite.
Theory Of Josephson-Type Oscillations In A Moving Charge-Density Wave - Errata, S. E. Barnes, A. Zawadowski
Theory Of Josephson-Type Oscillations In A Moving Charge-Density Wave - Errata, S. E. Barnes, A. Zawadowski
Physics Articles and Papers
Errata to Original Article: S. E. Barnes and A. Zawadowski, Theory of Josephson-Type Oscillations in a Moving Charge-Density Wave, Physical Review Letters, 51, 1499 (1983).
Theory Of Josephson-Type Oscillations In A Moving Charge-Density Wave, S. E. Barnes, A. Zawadowski
Theory Of Josephson-Type Oscillations In A Moving Charge-Density Wave, S. E. Barnes, A. Zawadowski
Physics Articles and Papers
A theory of Josephson-type phenomena is presented, in which the two macroscopic quantum states are the two components of an incommensurate charge-density wave with opposite wave vectors. The Fermi levels of these two states are split for a moving charge-density wave and impurity scattering induces quantum oscillations. Such oscillations may be responsible for the observed narrow-band noise in materials such as NbSe3 and TaS3.
Non-Mean-Field Interpretation Of The Irreversibility Line In Spin-Glasses, A. P. Malozemoff, S. E. Barnes, B. Barbara
Non-Mean-Field Interpretation Of The Irreversibility Line In Spin-Glasses, A. P. Malozemoff, S. E. Barnes, B. Barbara
Physics Articles and Papers
Susceptibility data on an amorphous GdAl spin-glass show an irreversibility onset line t=-A-H2/φ- and a susceptibility crossover line t=+A+H2/φ+ (t is reduced temperature; H is field). The exponents φ are both close to 3, and the amplitudes A differ only by a factor of 2. In contrast to earlier explanations of the irreversibility in terms of a de Almeida-Thouless mean-field instability, here both crossovers are explained in terms of a non-mean-field scaling theory.
Magnetic Resonance In The Spin-Glass (Lagd)Al2, M. Zomack, K. Baberschke, S. E. Barnes
Magnetic Resonance In The Spin-Glass (Lagd)Al2, M. Zomack, K. Baberschke, S. E. Barnes
Physics Articles and Papers
ESR has been measured in the spin-glass (La1-xGdx)Al2, 1≤x≤15 at.% for 1, 3, 9, and 35 GHz, corresponding to different applied magnetic fields and in the temperature range of 100 mK to 30 K. The comparison of data for different frequencies shows that the linewidth depends very much on the frequency and/or field and therefore the temperature Tmin of the linewidth minimum is not an intrinsic parameter and the shift of the resonance position is almost independent of frequency. The former effect is analyzed and theoretically explained in terms of the temperature dependence …
Γ8(3) Resonance In Esr Of (Ery)Al2 Single Crystals, U. Döbler, K. Baberschke, S. E. Barnes
Γ8(3) Resonance In Esr Of (Ery)Al2 Single Crystals, U. Döbler, K. Baberschke, S. E. Barnes
Physics Articles and Papers
Angle-dependent ESR results are given for 500-, 2500-, and 5000-ppm Er-doped YAl2 single crystals. An almost perfect analysis of the X- and Q-band data is achieved if the admixture of the first excited state Γ8(2) into the ground state Γ8(3) via the Zeeman interaction is taken into consideration. This enables us to determine the crystal electric field (CEF) parameter x=-0.322(20) and W=-0.29(2) K. The g-value shift yields N(EF)JΔg=+0.09(5) and the thermal broadening of the linewidth |N(EF)JΔH|=0.059(5). The precision of the experimental data allows, in principle, the determination …
Electron-Spin-Resonance Modes And The Edwards-Anderson Theory Of The Spin-Glass State, S. E. Barnes
Electron-Spin-Resonance Modes And The Edwards-Anderson Theory Of The Spin-Glass State, S. E. Barnes
Physics Articles and Papers
It is shown that the ESR modes observed in Cu: Mn alloys can be explained in terms of an Edwards-Anderson-type theory for a spin-glass when an anisotropy energy is included. Unlike other theories, the present one involves the conventional form for this anisotropy, UK=Ksin2θ, where θ is the angle the local microscopic magnetization makes with the symmetry rather than equilibrium direction. The present theory is distinguished by a predicted, but as yet unobserved, angular dependence of single-crystal samples with axial symmetry.