scholarly journals Square Lattice Iridates

2019 ◽  
Vol 10 (1) ◽  
pp. 315-336 ◽  
Author(s):  
Joel Bertinshaw ◽  
Y.K. Kim ◽  
Giniyat Khaliullin ◽  
B.J. Kim
Keyword(s):  
High Temperature ◽  
High Temperature Superconductivity ◽  
High Temperature Superconductors ◽  
Single Layer ◽  
Square Lattice ◽  
Spin Orbit Coupling ◽  
Fermi Arcs ◽  
Firm Evidence ◽  
Energy Physics ◽  
Strong Spin

Over the past few years, Sr2IrO4, a single-layer member of the Ruddlesden–Popper series iridates, has received much attention as a close analog of cuprate high-temperature superconductors. Although there is not yet firm evidence for superconductivity, a remarkable range of cuprate phenomenology has been reproduced in electron- and hole-doped iridates including pseudogaps, Fermi arcs, and d-wave gaps. Furthermore, many symmetry-breaking orders reminiscent of those decorating the cuprate phase diagram have been reported using various experimental probes. We discuss how the electronic structures of Sr2IrO4 through strong spin-orbit coupling leads to the low-energy physics that had long been unique to cuprates, what the similarities and differences between cuprates and iridates are, and how these advance the field of high-temperature superconductivity by isolating essential ingredients of superconductivity from a rich array of phenomena that surround it. Finally, we comment on the prospect of finding a new high-temperature superconductor based on the iridate series.

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

Electron-Doped High Tc Superconductors

MRS Bulletin ◽  
1990 ◽  
Vol 15 (6) ◽  
pp. 60-67 ◽  
Author(s):  
M. Brian Maple
Keyword(s):  
High Temperature ◽  
High Temperature Superconductivity ◽  
High Temperature Superconductors ◽  
Building Blocks ◽  
The United States ◽  
Charge Carriers ◽  
Critical Temperatures ◽  
High Tc ◽  
Prevailing View ◽  
Identical Crystal

Since the discovery of high temperature superconductivity in layered copper-oxide compounds in the latter part of 1986, an enormous amount of research has been carried out on these remarkable materials. Prior to 1989, the prevailing view was that the charge carriers responsible for superconductivity in these materials were holes that move through conducting CuO2 planes. The CuO2 planes are the basic building blocks of the crystal structures of all the presently known oxides with superconducting critical temperatures Tc greater than ~30 K. Recently, new superconducting materials have been discovered in Japan and the United States in which the charge carriers involved in the superconductivity appear to be electrons, rather than holes, that reside within the conducting CuO2 planes. These findings could have important implications regarding viable theories of high temperature superconductivity as well as strategies for finding new high temperature superconductors.The new electron-doped materials have the chemical formula Ln2-xMxCuO4-y and exhibit superconductivity with superconducting critical temperatures Tc as high as ~25 K for x ≍ 0.15 and y ≍ 0.02. Superconductivity has been discovered for M = Ce and Ln = Pr, Nd, Sm, and Eu, and for M = Th and Ln = Pr, Nd, and Sm. A related compound with the identical crystal structure, Nd2CuO4-x-y Fx, has also been found to display superconductivity withTc ≍ 25 K. Recently, it has been observed that superconductivity with Tc ≍ 25 K can even be induced in nonsuperconducting Nd2-xCexCuO4-y compounds by substituting Ga or In for Cu. Thus, it appears that the CuO2 planes can be doped with electrons, rendering the Ln2CuO4-y parent compounds metallic and superconducting, by substituting electron donor elements at sites within, as well as outside, the CuO2 planes; i.e., by substituting (1) Ce4+ or Th4+ ions for Ln3+ ions; (2) F1- ions for O2- ions; and (3) Ga3+ or In3+ ions for Cu2+ ions.

scholarly journals Optoelectronics with single layer group-VIB transition metal dichalcogenides

Nanophotonics ◽  
2018 ◽  
Vol 7 (10) ◽  
pp. 1589-1600 ◽  
Author(s):  
M.A. Khan ◽  
Michael N. Leuenberger
Keyword(s):  
Transition Metal ◽  
Electronic Devices ◽  
Transition Metal Dichalcogenides ◽  
Single Layer ◽  
Spin Orbit Coupling ◽  
Electroluminescent Devices ◽  
Metal Dichalcogenides ◽  
Fundamental Research ◽  
Excitonic Effects ◽  
Strong Spin

AbstractThe discovery of two-dimensional (2D) materials has opened up new frontiers and challenges for exploring fundamental research. Recently, single-layer (SL) transition metal dichalcogenides (TMDCs) have emerged as candidate materials for electronic and optoelectronic applications. In contrast to graphene, SL TMDCs have sizable band gaps that change from indirect to direct in SLs, which is useful in making thinner and more efficient electronic devices, such as transistors, photodetectors, and electroluminescent devices. In addition, SL TMDCs show strong spin-orbit coupling effects at the valence band edges, giving rise to the observation of valley-selective optical excitations. Here, we review the basic electronic and optical properties of pure and defected group-VIB SL TMDCs, with emphasis on the strong excitonic effects and their prospect for future optoelectronic devices.

EFFECTIVE THEORY FOR HIGH-TEMPERATURE SUPERCONDUCTIVITY BASED ON DUALITY AT S = 1/2 ANTIFERROMAGNETIC HEISENBERG MODEL

2005 ◽  
Vol 19 (12) ◽  
pp. 571-579 ◽  
Author(s):  
TAKAO MORINARI
Keyword(s):  
High Temperature ◽  
Heisenberg Model ◽  
High Temperature Superconductivity ◽  
High Temperature Superconductors ◽  
Parent Compound ◽  
High Energy ◽  
Field Application ◽  
Effective Theory ◽  
Dirac Fermions ◽  
Antiferromagnetic Heisenberg Model

It is argued that in two-dimension duality connects the CP1 representation of the S = 1/2 antiferromagnetic Heisenberg model with the Schwinger model in which Dirac fermions are interact via a U(1) gauge field. Application of this duality to underdoped high-temperature superconductors suggests that the high-energy fermionic excitation at the Mott insulating parent compound turns out to be a low-lying excitation in the spin disordered regime. A picture for high-temperature superconductivity is proposed.

Crystal Growth of High Temperature Superconductors

MRS Bulletin ◽  
1988 ◽  
Vol 13 (10) ◽  
pp. 56-61 ◽  
Author(s):  
H.J. Scheel ◽  
F. Licci
Keyword(s):  
High Temperature ◽  
Critical Current Density ◽  
Single Crystals ◽  
Critical Current ◽  
Current Density ◽  
Large Scale ◽  
High Temperature Superconductivity ◽  
High Temperature Superconductors ◽  
Superconducting Transition ◽  
Theoretical Understanding

The discovery of high temperature superconductivity (HTSC) in oxide compounds has confronted materials scientists with many challenging problems. These include the preparation of ceramic samples with critical current density of about 106 A/cm2 at 77 K and sufficient mechanical strength for large-scale electrotechnical and magnetic applications and the preparation of epitaxial thin films of high structural perfection for electronic devices.The main interest in the growth of single crystals is for the study of physical phenomena, which will help achieve a theoretical understanding of HTSC. Theorists still do not agree on the fundamental mechanisms of HTSC, and there is a need for good data on relatively defect-free materials in order to test the many models. In addition, the study of the role of defects like twins, grain boundaries, and dislocations in single crystals is important for understanding such parameters as the critical current density. The study of HTSC with single crystals is also expected to be helpful for finding optimum materials for the various applications and hopefully achieving higher values of the superconducting transition temperature Tc than the current maximum of about 125 K. It seems unlikely at present that single crystals will be used in commercial devices, but this possibility cannot be ruled out as crystal size and quality improve.

PAIRING STATE AND HIGH TEMPERATURE SUPERCONDUCTIVITY OF SEMI-LOCALIZED 2D ELECTRON SYSTEM WITH CIRCULAR MOLECULAR ORBITS

2002 ◽  
Vol 16 (10n11) ◽  
pp. 351-362 ◽  
Author(s):  
MASANORI SUGAHARA ◽  
NIKOLAI N. BOGOLUBOV
Keyword(s):  
High Temperature ◽  
Transition Temperature ◽  
Upper Bound ◽  
High Temperature Superconductivity ◽  
High Temperature Superconductors ◽  
Electron System ◽  
Circular Orbits ◽  
New Model ◽  
Pairing State ◽  
The Stability

Recently, new types of high temperature superconductors have been found which are characterized by the existence of circular molecular orbits in each unit site of 2D s/p electron system. In view of the characteristic, a new model of superconductivity is studied based on the stability of the correlated state of electrons in the 2D interconnection of circular orbits. This model gives an estimation of the upper bound of superfluidity transition temperature: T c ~ 130-400 K for fcc C 60, and T c ~ 110-340 K for hole-doped MgB 2.

scholarly journals Electronic origin of high-temperature superconductivity in single-layer FeSe superconductor

2012 ◽  
Vol 3 (1) ◽  
Author(s):  
Defa Liu ◽  
Wenhao Zhang ◽  
Daixiang Mou ◽  
Junfeng He ◽  
Yun-Bo Ou ◽  
...  
Keyword(s):  
High Temperature ◽  
High Temperature Superconductivity ◽  
Single Layer

Crystal Growth, Structure, and Incoherent Metallic Behaviour of FeCrAs

2011 ◽  
Vol 170 ◽  
pp. 276-281 ◽  
Author(s):  
Wen Long Wu ◽  
Alix McCollam ◽  
Ian P. Swainson ◽  
Stephen R. Julian
Keyword(s):  
High Temperature ◽  
High Temperature Superconductivity ◽  
High Temperature Superconductors ◽  
Magnetic Hysteresis ◽  
Freezing Temperature ◽  
Growth Structure ◽  
Preparation Conditions ◽  
Scattering Rate ◽  
Spin Freezing ◽  
Low Levels

There is growing interest in a possible connection between incoherent metallic conduction and high temperature superconductivity, that is exemplified by the behaviour of the parent compounds of the new iron-pnictide high-temperature superconductors. We have recently discovered very incoherent behaviour in the non-superconducting arsenide, FeCrAs. This material shows a non-metallic resistivity that rises with decreasing temperature without saturation or a gap, over three decades of temperature, from 80 mK to 800 K. We briefly review this behaviour, and address the question of disorder: how to test for the presence of disorder in a system where the scattering rate inferred from the resistivity is highly abnormal, and how to produce single crystals with low levels of disorder. Our discussion will focus on magnetic properties. FeCrAs is a partly frustrated magnetic system with a Nèel temperature TN that depends on sample quality, a sample-dependent spin freezing temperature TF < TN, and magnetic hysteresis that depends strongly on preparation conditions due to ferromagnetic minority phases in disordered samples.

Sign in / Sign up

Export Citation Format

Share Document