On the possibility of a first-order phase transition to the vortex state in layered superconductors (original) (raw)
Related papers
Properties of Vortex States in High Temperature Superconductors
2010
This paper reviews vortex behavior and formation of vortex liquid due to vortex lattice melting in high temperature superconductors (HTSC). The microscopic theory of superconductivity and the basic concepts needed to understand the magnetic properties of type magnetic phase diagrams are presented. The transition from the vortex solid to the vortex liquid phase for HTSC is described I and type II superconductors are discussed briefly. Magnetic states of superconductors are described and. Effects of the point, columnar disorders and strong thermal fluctuations on the character of the transition between these two phases are studied. The effects on the vortex solid to liquid transition of high magnetic fields applied parallel to the superconducting layers are also studied.
ac currents in a vortex state of layered superconductors
1998
The ac properties of layered superconductors in the vortex state for the parallel orientation of the external magnetic field B are examined. We find that due to an intrinsic Josephson effect the ac characteristics depend on the kind of the steady-state fluxon structure. Both the collective mode ⍀ ps and the ac penetration depth ʈ ac (,B) are affected by the magnetic field in an anomalous way, because of the reactive properties of the vortex state's environment.
Transport properties and structures of vortex matter in layered superconductors
Physical Review B, 2000
In this paper we analyze the structure, phase transitions and some transport properties of the vortex system when the external magnetic field lies parallel to the planes in layered superconductors. We show that experimental results for resistivity are qualitatively consistent with numerical simulations that describe the melting of a commensurate rotated lattice. However for some magnetic fields, the structure factor indicates the occurrence of smectic peaks at an intermediate temperature regime.
Disorder Driven Destruction of a Phase Transition in the Vortex System of a Superconductor
Physical Review Letters
We investigate the effects of point disorder on the magnetically induced vortex system of a layered superconductor. The clean system is known to have a first order phase transition which is clearly identified by a sharp peak in the specific heat. The peak is lost abruptly as the strength of the disorder is increased. Hence, for strong disorder there is no phase transition (in the vortex degrees of freedom) as a function of temperature but merely a crossover which is still detectable in the I-V characteristic.
Vortex Core Structure and Dynamics in Layered Superconductors
Vortices in Unconventional Superconductors and Superfluids, 2002
We investigate the equilibrium and nonequilibrium properties of the core region of vortices in layered superconductors. We discuss the electronic structure of singly and doubly quantized vortices for both s-wave and d-wave pairing symmetry. We consider the intermediate clean regime, where the vortex-core bound states are broadened into resonances with a width comparable to or larger than the quantized energy level spacing, and calculate the response of a vortex core to an a.c. electromagnetic field for vortices that are pinned to a metallic defect. We concentrate on the case where the vortex motion is nonstationary and can be treated by linear response theory. The response of the order parameter, impurity self energy, induced fields and currents are obtained by a self-consistent calculation of the distribution functions and the excitation spectrum. We then obtain the dynamical conductivity, spatially resolved in the region of the core, for external frequencies in the range, 0.1∆ < ω < ∼ 3∆. We also calculate the dynamically induced charge distribution in the vicinity of the core. This charge density is related to the nonequilibrium response of the bound states and collective mode, and dominates the electromagnetic response of the vortex core.
The phase diagram of vortex matter in layered superconductors with tilted columnar pinning centers
2009
We study the vortex matter phase diagram of a layered superconductor in the presence of columnar pinning defects, tilted with respect to the normal to the layers. We use numerical minimization of the free energy written as a functional of the time averaged vortex density of the Ramakrishnan-Yussouff form, supplemented by the appropriate pinning potential. We study the case where the pin density is smaller than the areal vortex density. At lower pin concentrations, we find, for temperatures of the order of the melting temperature of the unpinned lattice, a Bose glass type phase which at lower temperatures converts, via a first order transition, to a Bragg glass, while, at higher temperatures, it crosses over to an interstitial liquid. At somewhat higher concentrations, no transition to a Bragg glass is found even at the lowest temperatures studied. While qualitatively the behavior we find is similar to that obtained using the same procedures for columnar pins normal to the layers, th...
Phase diagram of the vortex system in layered superconductors with strong columnar pinning
Physical Review B - PHYS REV B, 2005
We present the results of a detailed investigation of the low-temperature properties of the vortex system in strongly anisotropic layered superconductors with a random array of columnar pinning centers. Our method involves numerical minimization of a free energy functional in terms of the time-averaged local vortex density. It yields the detailed vortex density distribution for all local free-energy minima, and therefore allows the computation of any desired correlation function of the time-averaged local vortex density. Results for the phase diagram in the temperature vs pin concentration plane at constant magnetic induction are presented. We confirm that for very low pin concentrations, the low-temperature phase is a Bragg glass, which melts into an interstitial liquid phase via two first-order steps, separated by a Bose glass phase. At higher concentrations, however, the low-temperature phase is a Bose glass, and the melting transition becomes continuous. The transition is then c...
Physical Review B
In this work we revisit the vortex matter phase diagram in layered superconductors solving still open questions by means of AC and DC local magnetic measurements in the paradigmatic Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8}$ compound. We show that measuring with AC magnetic techniques is mandatory in order to probe the bulk response of vortex matter, particularly at high-temperatures where surface barriers for vortex entrance dominate. From the TrmFOTT_{\rm FOT}TrmFOT-evolution of the enthalpy and latent-heat at the transition we find that, contrary to previous reports, the nature of the dominant interlayer coupling is electromagnetic in the whole temperature range. By studying the dynamic properties of the phase located at TgtrsimTrmFOTT \gtrsim T_{\rm FOT}TgtrsimTrmFOT, we reveal the spanning in a considerable fraction of the phase diagram of a non-linear vortex phase suggesting bulk pinning might play a role even in the liquid vortex phase.
Phase diagram of vortex matter in layered superconductors with tilted columnar pinning centers
Physical Review B, 2009
We study the vortex matter phase diagram of a layered superconductor in the presence of columnar pinning defects, tilted with respect to the normal to the layers. We use numerical minimization of the free energy written as a functional of the time averaged vortex density of the Ramakrishnan-Yussouff form, supplemented by the appropriate pinning potential. We study the case where the pin density is smaller than the areal vortex density. At lower pin concentrations, we find, for temperatures of the order of the melting temperature of the unpinned lattice, a Bose glass type phase which at lower temperatures converts, via a first order transition, to a Bragg glass, while, at higher temperatures, it crosses over to an interstitial liquid. At somewhat higher concentrations, no transition to a Bragg glass is found even at the lowest temperatures studied. While qualitatively the behavior we find is similar to that obtained using the same procedures for columnar pins normal to the layers, there are important and observable quantitative differences, which we discuss.
Vortex lattice transition in d-wave superconductors
Physical Review B, 1999
Making use of the extended Ginzburg Landau theory, which includes the fourth order derivative term, we study the vortex state in a magnetic field parallel to the c axis. The vortex core structure is distorted due to this higher order term, which reveals the fourfold symmetry. Further, this distortion gives rise to the core interaction energy, which favors a square lattice tilted by 45 • from the a axis. The critical field of this transition is determined. The magnetization diverges at the transition. This suggests the transition is of the first order.