scholarly journals Unusual behavior of cuprates explained by heterogeneous charge localization

2019 ◽  
Vol 5 (1) ◽  
pp. eaau4538 ◽  
Author(s):  
D. Pelc ◽  
P. Popčević ◽  
M. Požek ◽  
M. Greven ◽  
N. Barišić
Keyword(s):  
Phase Diagram ◽  
High Temperature Superconductivity ◽  
Linear Temperature Dependence ◽  
Unusual Behavior ◽  
Linear Temperature ◽  
Doping Dependence ◽  
Charge Localization ◽  
Past Half Century ◽  
Liquid Behavior ◽  
Superconducting Pairing

The discovery of high-temperature superconductivity in cuprates ranks among the major scientific milestones of the past half century, yet pivotal questions regarding the complex phase diagram of these materials remain unanswered. Generally thought of as doped charge-transfer insulators, these complex oxides exhibit pseudogap, strange-metal, superconducting, and Fermi liquid behavior with increasing hole-dopant concentration. Motivated by recent experimental observations, here we introduce a phenomenological model wherein exactly one hole per planar copper-oxygen unit is delocalized with increasing doping and temperature. The model is percolative in nature, with parameters that are highly consistent with experiments. It comprehensively captures key unconventional experimental results, including the temperature and the doping dependence of the pseudogap phenomenon, the strange-metal linear temperature dependence of the planar resistivity, and the doping dependence of the superfluid density. The success and simplicity of the model greatly demystify the cuprate phase diagram and point to a local superconducting pairing mechanism.

scholarly journals What is strange about high-temperature superconductivity in cuprates?

2017 ◽  
Vol 31 (25) ◽  
pp. 1745005
Author(s):  
I. Božović ◽  
X. He ◽  
J. Wu ◽  
A. T. Bollinger
Keyword(s):  
Phase Diagram ◽  
Cuprate Superconductors ◽  
High Temperature Superconductivity ◽  
Einstein Condensation ◽  
Strongly Correlated ◽  
Bose Einstein Condensation ◽  
Ultimate Question ◽  
Underdoped Cuprates ◽  
Bose Einstein ◽  
Superconducting Parameters

Cuprate superconductors exhibit many features, but the ultimate question is why the critical temperature ([Formula: see text]) is so high. The fundamental dichotomy is between the weak-pairing, Bardeen–Cooper–Schrieffer (BCS) scenario, and Bose–Einstein condensation (BEC) of strongly-bound pairs. While for underdoped cuprates it is hotly debated which of these pictures is appropriate, it is commonly believed that on the overdoped side strongly-correlated fermion physics evolves smoothly into the conventional BCS behavior. Here, we test this dogma by studying the dependence of key superconducting parameters on doping, temperature, and external fields, in thousands of cuprate samples. The findings do not conform to BCS predictions anywhere in the phase diagram.

A DOMAIN MODEL OF CUPRATES

1994 ◽  
Vol 08 (22) ◽  
pp. 3083-3094 ◽  
Author(s):  
V. DALLACASA
Keyword(s):  
Fermi Liquid ◽  
Characteristic Length ◽  
Domain Model ◽  
Linear Temperature Dependence ◽  
Arbitrary Length ◽  
Linear Temperature ◽  
Bcs Model ◽  
Marginal Fermi Liquid ◽  
System Length ◽  
Enhanced Superconductivity

We have investigated the occurrence of superconductivity in a Fermi liquid of finite volume, under the assumption of a sharp surface, by solving numerically (at arbitrary length) and analytically (at the smallest lengths) the Cooper–BCS model. We find that this model can predict enhanced superconductivity with respect to the bulk BCS model when the system length L ≪ L0, in which L0 is a characteristic length. Under the same conditions the normal state is found to behave anomalously with respect to the conventional Fermi liquid, with a linear temperature dependence of the resistivity and marginal Fermi liquid properties. The results are used to implement a domain model of high T c superconductors.

scholarly journals Bad metallic transport in a cold atom Fermi-Hubbard system

Science ◽  
2018 ◽  
Vol 363 (6425) ◽  
pp. 379-382 ◽  
Author(s):  
Peter T. Brown ◽  
Debayan Mitra ◽  
Elmer Guardado-Sanchez ◽  
Reza Nourafkan ◽  
Alexis Reymbaut ◽  
...  
Keyword(s):  
Diffusion Constant ◽  
Cold Atom ◽  
Quantum Systems ◽  
Strong Interactions ◽  
Einstein Relation ◽  
Linear Temperature Dependence ◽  
Many Body ◽  
Linear Temperature ◽  
Density Modulation ◽  
Shed Light

Strong interactions in many-body quantum systems complicate the interpretation of charge transport in such materials. To shed light on this problem, we study transport in a clean quantum system: ultracold lithium-6 in a two-dimensional optical lattice, a testing ground for strong interaction physics in the Fermi-Hubbard model. We determine the diffusion constant by measuring the relaxation of an imposed density modulation and modeling its decay hydrodynamically. The diffusion constant is converted to a resistivity by using the Nernst-Einstein relation. That resistivity exhibits a linear temperature dependence and shows no evidence of saturation, two characteristic signatures of a bad metal. The techniques we developed in this study may be applied to measurements of other transport quantities, including the optical conductivity and thermopower.

scholarly journals Modelling the structural variation of quartz and germanium dioxide with temperature by means of transformed crystallographic data

2021 ◽  
Vol 77 (3) ◽  
Author(s):  
Maximilian Fricke ◽  
Noel W. Thomas
Keyword(s):  
Structure Prediction ◽  
Structural Variation ◽  
Germanium Dioxide ◽  
Reverse Transformation ◽  
Linear Temperature Dependence ◽  
Structural Analogue ◽  
Acta Cryst ◽  
Linear Temperature ◽  
First Order ◽  
Angle Parameter

The pseudocubic (PC) parameterization of O4 tetrahedra [Reifenberg & Thomas (2018). Acta Cryst. B74, 165–181] is applied to quartz (SiO2) and its structural analogue germanium dioxide (GeO2). In α-quartz and GeO2, the pseudocubes are defined by three length parameters, a PC, b PC and c PC, together with an angle parameter αPC. In β-quartz, αPC has a fixed value of 90°. For quartz, the temperature evolution of parameters for the pseudocubes and the silicon ion network is established by reference to the structural refinements of Antao [Acta Cryst. (2016), B72, 249–262]. In α-quartz, the curve-fitting employed to express the non-linear temperature dependence of pseudocubic length and Si parameters exploits the model of a first-order Landau phase transition utilized by Grimm & Dorner [J. Phys. Chem. Solids (1975), 36, 407–413]. Since values of tetrahedral tilt angles about 〈100〉 axes also result from the pseudocubic transformation, a curve for the observed non-monotonic variation of αPC with temperature can also be fitted. Reverse transformation of curve-derived values of [Si+PC] parameters to crystallographic parameters a, c, x Si, x O, y O and z O at interpolated or extrapolated temperatures is demonstrated for α-quartz. A reverse transformation to crystallographic parameters a, c, x O is likewise carried out for β-quartz. This capability corresponds to a method of structure prediction. Support for the applicability of the approach to GeO2 is provided by analysing the structural refinements of Haines et al. [J. Solid State Chem. (2002), 166, 434–441]. An analysis of trends in tetrahedral distortion and tilt angle in α-quartz and GeO2 supports the view that GeO2 is a good model for quartz at high pressure.

scholarly journals Phase diagram and electronic indication of high-temperature superconductivity at 65 K in single-layer FeSe films

2013 ◽  
Vol 12 (7) ◽  
pp. 605-610 ◽  
Author(s):  
Shaolong He ◽  
Junfeng He ◽  
Wenhao Zhang ◽  
Lin Zhao ◽  
Defa Liu ◽  
...  
Keyword(s):  
Phase Diagram ◽  
High Temperature ◽  
High Temperature Superconductivity ◽  
Single Layer
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