Theories of High Tc Superconductors

1987 ◽  
Vol 99 ◽  
Author(s):  
John Bardeen
Keyword(s):  
Low Temperatures ◽  
Landau Theory ◽  
3D Models ◽  
Oxide Superconductors ◽  
High Tc Superconductors ◽  
Pairing Interaction ◽  
Ginzburg Landau ◽  
High Tc ◽  
Wide Range ◽  
High Transition

ABSTRACTMany theories have been given to account for the high transition temperatures in the oxide superconductors. While most are based on pairing, they differ as to the origin of the attractive interaction that gives rise to the pairs and whether the pairing is weak or strong. If weak(λ < ∼ 0.5), the energy range of the pairing interaction must be wider than is consistent with one mediated solely by phonons. With measurements on single crystals becoming available, giving data covering a wide range of frequencies and temperatures, it is possible to narrow down the possible options. The data show that anisotropie 3D models are required. Observed isotope shifts indicate that phonons must play a role, but additional mechanisms are likely necessary to account for the high T's. Thermal, magnetic and transport data are consistent with anisotropie Ginzburg-Landau theory near T, with expected departures at low temperatures.

CRITICAL TEMPERATURE OF HIGH-Tc SUPERCONDUCTORS AND BOUNDARY CONDITIONS IN GINZBURG-LANDAU THEORY

2009 ◽  
Vol 23 (20n21) ◽  
pp. 4269-4276 ◽  
Author(s):  
A. LYKOV
Keyword(s):  
Boundary Condition ◽  
Critical Temperature ◽  
Order Parameter ◽  
Cuprate Superconductors ◽  
Landau Theory ◽  
Structural Elements ◽  
High Tc Superconductors ◽  
Ginzburg Landau ◽  
High Tc ◽  
Insulating Properties

New boundary condition for the order parameter in the Ginzburg-Landau theory is applied to the case of CuO 2 planes which are the main structural elements responsible for superconductivity in high-Tc superconductors. It was found that the order parameter in these superconductors is significantly depressed in the CuO 2 planes. As a result, this boundary condition to the GL equations is found to limit the critical temperature of high-Tc superconductors. Thus, in order to increase Tc of cuprate superconductors, the number of CuO 2 planes that are within a short distance of each other in unit cell or insulating properties of the layers located in the vicinity to the CuO 2 planes should be increased.

Generalised Ginzburg-Landau theory for high Tc superconductors

1988 ◽  
Vol 153-155 ◽  
pp. 671-672 ◽  
Author(s):  
T.C. Choy ◽  
M.P. Das ◽  
Hong-Xing He
Keyword(s):  
Landau Theory ◽  
High Tc Superconductors ◽  
Ginzburg Landau ◽  
High Tc

Identifying the Pairing Mechanism in High-Tc Superconductors

1989 ◽  
Vol 156 ◽  
Author(s):  
J.B. Goodenough ◽  
A. Manthiram ◽  
J. Zhou
Keyword(s):  
Stress Relief ◽  
Redox Couple ◽  
Oxide Superconductors ◽  
High Tc Superconductors ◽  
Pairing Mechanism ◽  
Strong Electron ◽  
High Tc ◽  
Two Factors ◽  
High Transition ◽  
Copper Oxide Superconductors

ABSTRACTIt is argued that the origin of the high transition temperatures observed in Ba1−xKxBiO3 and the copper-oxide superconductors with perovskite-related structures is due to two factors: (1) overlap of a partially filled σ* band of primarily cation character and a π or π* band of mostly O-2pπ parentage permits charge transfer between cation and anion subarrays with oxygen-atom displacement perpendicular to a M-O-M bond axis and (2) bondlength mismatch places the M-O-M bondlength under a compressive or tensile stress. Relief of a compressive stress by the bending of a M-O-M bond from 180° introduces a strong electron-lattice interaction with holes; a 180° Cu-O-Cu bond allows strong electronlattice coupling with electrons of a Cu2+/+ redox couple, but not with holes in a Cu3+/2+redox couple.

POSSIBLE MECHANISM OF PAIRING IN HIGH Tc SUPERCONDUCTORS: A MULTI-COMPONENT PLASMA MODEL

1988 ◽  
Vol 02 (05) ◽  
pp. 873-881
Author(s):  
J. Mahanty ◽  
M. P. Das
Keyword(s):  
Interaction Potential ◽  
Oxide Superconductors ◽  
Plasma Model ◽  
High Tc Superconductors ◽  
High Tc ◽  
Gap Equation ◽  
Ion Plasma ◽  
Electrons And Ions ◽  
Component Plasma ◽  
High Transition

Screening of a pair of point charges in a medium of electrons and ions is studied using the hydrodynamical model, treating the system as a multi-component plasma. When some of the ion plasma branches possess negative dispersion, the interaction potential of the pair can become attractive and large in certain regions of momentum space under certain conditions. By using this potential in the BCS gap equation, high transition temperatures have been obtained. Applicability of this model to oxide superconductors is discussed.

Ginzburg–Landau Theory of Condensates

2021 ◽  
Author(s):  
Baruch Rosenstein ◽  
Dingping Li
Keyword(s):  
Graduate Students ◽  
Landau Theory ◽  
Condensed Matter ◽  
Condensed Matter Physics ◽  
High Tc Superconductors ◽  
Ginzburg Landau ◽  
High Tc ◽  
Topological Excitations ◽  
Ordered Phases

Ginzburg–Landau theory is an important tool in condensed matter physics research, describing the ordered phases of condensed matter, including the dynamics, elasticity, and thermodynamics of the condensed configurations. In this systematic introduction to Ginzberg–Landau theory, both common and topological excitations are considered on the same footing (including their thermodynamics and dynamical phenomena). The role of the topological versus energetic considerations is made clear. Required mathematics (symmetry, including lattice translation, topology, and perturbative techniques) are introduced as needed. The results are illustrated using arguably the most fascinating class of such systems, high Tc superconductors subject to magnetic field. This book is an important reference for both researchers and graduate students working in condensed matter physics or can act as a textbook for those taking advanced courses on these topics.

A GINZBURG-LANDAU THEORY FOR CRITICAL TEMPERATURE OF LAYERED HIGH-Tc SUPERCONDUCTORS

1989 ◽  
Vol 03 (18) ◽  
pp. 1393-1400
Author(s):  
TATSUYA NAGAO ◽  
HIROYUKI MORI ◽  
FUMIKO YONEZAWA
Keyword(s):  
Experimental Data ◽  
Critical Temperature ◽  
Layered Structure ◽  
Phenomenological Model ◽  
Landau Theory ◽  
Single Layer ◽  
High Tc Superconductors ◽  
Ginzburg Landau ◽  
High Tc ◽  
Periodic Layered Structure

Using a phenomenological model for layered superconductors, we derive a formalism for the critical temperature T c in terms of the layer numbers. We show that T c of a system of n identical layers is the same as that of a single layer for all values of n. In a periodic layered structure composed of two kinds of layers, T c increases monotonically with the number of higher-T c layers. When the carrier number depends on structure, T c shows a behavior consistent with the experimental data on some high-T c superconductors such as Tl and Bi families. We make a suggestion to achieve a higher T c .

scholarly journals Possible Alterations of Local Gravitational Field Inside a Superconductor

Entropy ◽  
2021 ◽  
Vol 23 (2) ◽  
pp. 193 ◽  
Author(s):  
Giovanni Alberto Ummarino ◽  
Antonio Gallerati
Keyword(s):  
Gravitational Field ◽  
Landau Theory ◽  
Time Dependent ◽  
Qualitative Comparison ◽  
Ginzburg Landau ◽  
High Tc ◽  
Gravitational Fields ◽  
Favorable Conditions

We calculate the possible interaction between a superconductor and the static Earth’s gravitational fields, making use of the gravito-Maxwell formalism combined with the time-dependent Ginzburg–Landau theory. We try to estimate which are the most favorable conditions to enhance the effect, optimizing the superconductor parameters characterizing the chosen sample. We also give a qualitative comparison of the behavior of high–Tc and classical low–Tc superconductors with respect to the gravity/superfluid interplay.

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