Disordered type-II superconductors: a universal phase diagram for low-Tc systems

Banerjee, S. S.; Grover, A. K.; Higgins, M. J.; Menon, Gautam I.; Mishra, Prerna; Pal, D.; Ramakrishnan, S.; Rao, T. V. Chandrasekhar; Ravikumar, G.; Sahni, V. C.; Sarkar, Sreemoyee; Tomy, C. V.

doi:10.1016/s0921-4534(00)01767-6

Cited by 45 publications

(109 citation statements)

References 58 publications

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“…In contrast, for most low-T c systems, such disordered phases occupy a relatively small regime just below T c (H). The phase behaviour in the mixed phase of low-T c superconductors has been the focus of recent attention [31][32][33][34][35]. These studies suggest a universal phase diagram for weakly pinned low-T c type-II materials [35].…”

Section: Much Theoretical Attention Hasmentioning

confidence: 99%

“…This can result in large noise signals [36] associated with a small number of fluctuators [36,53], intermediate structure in the ac susceptibility as a function of T [31,34], a stepwise expulsion of vortices [54], strong thermal instabilities [36,55] and a host of other phenomena specific to this phase [35], all features of the experimental data, which are hard to rationalize in other pictures.…”

Section: Much Theoretical Attention Hasmentioning

confidence: 99%

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Phase behavior of type-II superconductors with quenched point pinning disorder: A phenomenological proposal

Menon

2002

Phys. Rev. B

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A general phenomenology for phase behaviour in the mixed phase of type-II superconductors with weak point pinning disorder is outlined. We propose that the "Bragg glass" phase generically transforms via two separate thermodynamic phase transitions into a disordered liquid on increasing the temperature. The first transition is into a glassy phase, topologically disordered at the largest length scales; current evidence suggests that it lacks the longranged phase correlations expected of a "vortex glass". This phase has a significant degree of short-ranged translational order, unlike the disordered liquid, but no quasi-long range order, in contrast to the Bragg glass. This glassy phase, which we call a "multi-domain glass", is confined to a narrow sliver at intermediate fields, but broadens out both for much larger and much smaller field values. The multi-domain glass may be a "hexatic glass"; alternatively, its glassy properties may originate in the replica symmetry breaking envisaged in recent theories of the structural glass transition. Estimates for translational correlation lengths in the multi-domain glass indicate that * Email:menon@imsc.ernet.in 1 they can be far larger than the interline spacing for weak disorder, suggesting a plausible mechanism by which signals of a two-step transition can be obscured. Calculations of the Bragg glass-multi-domain glass and the multidomain glass-disordered liquid phase boundaries are presented and compared to experimental data. We argue that these proposals provide a unified picture of the available experimental data on both high-T c and low-T c materials, simulations and current theoretical understanding.

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Section: Much Theoretical Attention Hasmentioning

confidence: 99%

Section: Much Theoretical Attention Hasmentioning

confidence: 99%

Phase behavior of type-II superconductors with quenched point pinning disorder: A phenomenological proposal

Menon

2002

Phys. Rev. B

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“…In this case the resulting phase diagram looks like that of low-T c superconductors. [1][2][3][4][5] The transition from one type of phase diagram to the other occurs when D = c L .…”

Section: Types Of Phase Diagramsmentioning

confidence: 99%

“…[1][2][3][4][5] In the high-T c YBaCuO crystals, the line of the maximum critical current density, H p (T ), frequently lies essentially below the irreversibility line in the H − T plane, [6][7][8][9] and in sufficiently perfect crystals it exhibits nonmonotonic behavior with temperature. [10][11][12][13][14][15][16] In these perfect crystals the line of maximum current density approaches the flux-line melting line, H m (T ), approximately at the so-called upper critical point 17 at which the melting line terminates.…”

Section: Introductionmentioning

confidence: 99%

“…18 At present the origin of the peak effect in low-T c and high-T c superconductors is commonly associated with the proliferation of dislocations in the flux-line lattice. [1][2][3][4][5][10][11][12][13][14][15][16] At this first order phase transition 3,[19][20][21][22] induced by quenched disorder in the vortex system, a transformation of a quasiordered Bragg glass 23 into a disordered amorphous vortex phase occurs. Although different criteria 3,[12][13][14] are used for determining the exact position of this transition on the peak-shaped dependence of the critical current density on H, they all lead to qualitatively similar H − T phase diagrams, and, for definiteness only, we shall imply below that the phase transition corresponds to the line of the maximum critical current density, H p (T ).…”

Section: Introductionmentioning

confidence: 99%

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Peak effect, vortex-lattice melting line, and order-disorder transition in conventional and high-Tcsuperconductors

2001

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We investigate the order-disorder transition line from a Bragg glass to an amorphous vortex glass in the H − T phase diagram of three-dimensional type-II superconductors taking into account both pinning-caused and thermal fluctuations of the vortex lattice. Our approach is based on the Lindemann criterion and on results of the collective pinning theory and generalizes previous work of other authors. It is shown that the shapes of the order-disorder transition line and the vortex lattice melting curve are determined only by the Ginzburg number, which characterizes thermal fluctuations, and by a parameter which describes the strength of the quenched disorder in the fluxline lattice. In the framework of this unified approach we obtain the H − T phase diagrams for both conventional and high-Tc superconductors. Several well-known experimental results concerning the fishtail effect and the phase diagram of high-Tc superconductors are naturally explained by assuming that a peak effect in the critical current density versus H signalizes the order-disorder transition line in superconductors with point defects.

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Effect of pinning and driving force on the metastability effects in weakly pinned superconductors and the determination of spinodal line pertaining to order—disorder transition

et al. 2006

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We explore the effect of varying drive on metastability features exhibited by the vortex matter in single crystals of 2H-NbSe 2 and CeRu 2 with varying degree of random pinning. The metastable nature of vortex matter is reflected in the path dependence of the critical current density, which in turn is probed in a contact-less way via ac-susceptibility measurements. The sinusoidal ac magnetic field applied during ac susceptibility measurements appears to generate a driving force on the vortex matter. In a nascent pinned single crystal of 2H-NbSe 2 , where the peak effect (PE) pertaining to the order-disorder phenomenon is a sharp first order like transition, the supercooling feature below the peak temperature is easily wiped out by the reorganization caused by the ac driving force. In this paper, we elucidate the interplay between the drive and the pinning which can conspire to make the path dependent ac-susceptibility response of different metastable vortex states appear identical. An optimal balance between the pinning and driving force is needed to view the metastability effects in typically weakly pinned specimen of low temperature superconductors. As one uses samples with larger pinning in order to differentiate the response of different metastable vortex states, one encounters a new phenomena, viz., the second magnetization peak (SMP) anomaly prior to the PE. Supercooling/superheating can occur across both the PE and the SMP anomaly and both of these are known to display non-linear characteristic as well. Interplay between the path dependence in the critical current density and the non-linearity in the electromagnetic response determine the metastability effects seen in first and the third harmonic response of the ac susceptibility across the temperature regions of the SMP and the PE. The limiting temperature above which metastability effects cease can be conveniently located in the third harmonic data, and the observed behavior can be rationalized within the Beans Critical State model. A vortex phase diagram showing the different vortex phases for a typically weakly pinned specimen has been constructed via the ac susceptibility data in a crystal of 2H-NbSe 2 which shows the SMP and the PE anomalies. The phase space of coexisting weaker and stronger pinned regions has been identified. It can be bifurcated into two parts, where the order and disorder dominate, respectively. The former part continuously connects to the reentrant disordered vortex phase pertaining to the small bundle pinning regime, where the vortices are far apart, interaction effects are weak and the polycrystalline form of flux line lattice prevails.

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Disordered type-II superconductors: a universal phase diagram for low-Tc systems

Cited by 45 publications

References 58 publications

Phase behavior of type-II superconductors with quenched point pinning disorder: A phenomenological proposal

Phase behavior of type-II superconductors with quenched point pinning disorder: A phenomenological proposal

Peak effect, vortex-lattice melting line, and order-disorder transition in conventional and high-Tcsuperconductors

Effect of pinning and driving force on the metastability effects in weakly pinned superconductors and the determination of spinodal line pertaining to order—disorder transition

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