Noise probes of underlying static correlation lengths in the superconducting peak effect

Rabin, Michael W.; Merithew, R. D.; Weissman, M. B.; Higgins, M. J.; Bhattacharya, S.

doi:10.1103/physrevb.57.r720

Cited by 27 publications

(26 citation statements)

References 15 publications

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“…We find that an ac field of 50 Oe (at ഠ0.1 Hz, using the superconducting magnet at nonpersistent mode) can crystallize the disordered FC states at T , T p . The shaking effects of an ac magnetic field were observed in transport [20] and ac magnetization [21] in the peak-effect region in 2H-NbSe2, and were interpreted as vortex reordering, consistent with our direct observations here.…”

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confidence: 90%

Superheating and Supercooling of Vortex Matter in a Nb Single Crystal: Direct Evidence for a Phase Transition at the Peak Effect from Neutron Diffraction

2001

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We report the first observation of a striking history dependence of the structure function of vortex matter in the peak effect regime in a Nb single crystal by using small angle neutron scattering combined with in situ magnetic susceptibility measurements. Metastable phases of vortex matter, supercooled vortex liquid and superheated vortex solid, have been identified. We interpret our results as direct structural evidence for a first-order vortex solid-liquid transition at the peak effect.

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confidence: 90%

Superheating and Supercooling of Vortex Matter in a Nb Single Crystal: Direct Evidence for a Phase Transition at the Peak Effect from Neutron Diffraction

2001

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“…(6) Figure 16(b) shows the noise power S 0 [86], obtained by integrating S(ω) over a fixed frequency range, S 0 = ω1 ω2 df S(ω). In the plastic flow phase, S(ω) has the form S(ω) ∝ 1/f α with α = 1.5 to 2.0, indicating the existence of large noise power at low frequencies due to the slowly changing plastic flow channel structure similar to that illustrated in figure 1(a).…”

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confidence: 99%

Depinning and nonequilibrium dynamic phases of particle assemblies driven over random and ordered substrates: a review

2016

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Abstract. We review the depinning and nonequilibrium phases of collectively interacting particle systems driven over random or periodic substrates. This type of system is relevant to vortices in type-II superconductors, sliding charge density waves, electron crystals, colloids, stripe and pattern forming systems, and skyrmions, and could also have connections to jamming, glassy behaviors, and active matter. These systems are also ideal for exploring the broader issues of characterizing transient and steady state nonequilibrium flow phases as well as nonequilibrium phase transitions between distinct dynamical phases, analogous to phase transitions between different equilibrium states. We discuss the differences between elastic and plastic depinning on random substrates and the different types of nonequilibrium phases which are associated with specific features in the velocity-force curves, fluctuation spectra, scaling relations, and local or global particle ordering. We describe how these quantities can change depending on the dimension, anisotropy, disorder strength, and the presence of hysteresis. Within the moving phase we discuss how there can be a transition from a liquid-like state to dynamically ordered moving crystal, smectic, or nematic states. Systems with periodic or quasiperiodic substrates can have multiple nonequilibrium second or first order transitions in the moving state between chaotic and coherent phases, and can exhibit hysteresis. We also discuss systems with competing repulsive and attractive interactions, which undergo dynamical transitions into stripes and other complex morphologies when driven over random substrates. Throughout this work we highlight open issues and future directions such as absorbing phase transitions, nonequilibrium work relations, inertia, the role of non-dissipative dynamics such as Magnus effects, and how these results could be extended to the broader issues of plasticity in crystals, amorphous solids, and jamming phenomena.

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“…Noise fluctuations have also been used as another method to study the dynamics of magnetic systems [32]. In superconducting vortex systems, the plastic flow regime is associated with large voltage noise fluctuations of a f 1 form [33][34][35][36], while when the system dynamically orders at higher drives, narrow band noise features appear and the noise power is strongly reduced [26,[37][38][39]. Here we show that changes in the skyrmion Hall angle are correlated with changes in the skyrmion velocity fluctuations and the shape of the velocity noise spectrum.…”

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confidence: 99%

Noise fluctuations and drive dependence of the skyrmion Hall effect in disordered systems

2016

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Using a particle-based simulation model, we show that quenched disorder creates a drive-dependent skyrmion Hall effect as measured by the change in the ratio =R V V of the skyrmion velocity perpendicular (V ⊥ ) and parallel (V ) to an external drive. R is zero at depinning and increases linearly with increasing drive, in agreement with recent experimental observations. At sufficiently high drives where the skyrmions enter a free flow regime, R saturates to the disorder-free limit. This behavior is robust for a wide range of disorder strengths and intrinsic Hall angle values, and occurs whenever plastic flow is present. For systems with small intrinsic Hall angles, we find that the Hall angle increases linearly with external drive, as also observed in experiment. In the weak pinning regime where the skyrmion lattice depins elastically, R is nonlinear and the net direction of the skyrmion lattice motion can rotate as a function of external drive. We show that the changes in the skyrmion Hall effect correlate with changes in the power spectrum of the skyrmion velocity noise fluctuations. The plastic flow regime is associated with f 1 noise, while in the regime in which R has saturated, the noise is white with a weak narrow band signal, and the noise power drops by several orders of magnitude. At low drives, the velocity noise in the perpendicular and parallel directions is of the same order of magnitude, while at intermediate drives the perpendicular noise fluctuations are much larger.

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Noise probes of underlying static correlation lengths in the superconducting peak effect

Cited by 27 publications

References 15 publications

Superheating and Supercooling of Vortex Matter in a Nb Single Crystal: Direct Evidence for a Phase Transition at the Peak Effect from Neutron Diffraction

Superheating and Supercooling of Vortex Matter in a Nb Single Crystal: Direct Evidence for a Phase Transition at the Peak Effect from Neutron Diffraction

Depinning and nonequilibrium dynamic phases of particle assemblies driven over random and ordered substrates: a review

Noise fluctuations and drive dependence of the skyrmion Hall effect in disordered systems

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