Theory of the Normal State of Cuprate Superconductors

1989 ◽  
Vol 169 ◽  
Author(s):  
Philip W. Anderson ◽  
Yong Ren

AbstractWe propose a framework for the theory of the "normal" metallic state of the CuO2 planes of high Tc superconductors. This state is closely analogous to the known state of the one-dimensional Hubbard model, with spin excitations which can be thought of as chargeless (Z = 0) Fermions occupying the interior of the conventional Fermi surface, and charged excitations which have zero energy near the spanning vectors 2kF of that Fermi surface. The electron spectrum is the composite spectrum of two of these excitations, and can be fitted to angle-resolved photoemission data. When we do so we can calculate or estimate many properties of the normal state in excellent agreement with experiment, and show that the pair susceptibility is anomalously large and temperature-dependent, explaining the high Tc and the specific heat behavior.

1998 ◽  
Vol 12 (05) ◽  
pp. 173-180 ◽  
Author(s):  
P. A. Marchetti ◽  
Zhao-Bin Su ◽  
Lu Yu

The U(1)×SU(2) Chern–Simons gauge theory is applied to study the 2D t–J model describing the normal state of underdoped cuprate superconductors. The U(1) field produces a flux phase for holons converting them into Dirac-like fermions, while the SU(2) field, due to the coupling to holons gives rise to a gap for spinons. An effective low-energy action involving holons, spinons and a self-generated U(1) gauge field is derived. The Fermi surface and electron spectral function obtained are consistent with photoemission experiments. The theory predicts a minimal gap proportional to doping concentration. It also explains anomalous transport properties.


2020 ◽  
Vol 11 (1) ◽  
pp. 213-229 ◽  
Author(s):  
Richard L. Greene ◽  
Pampa R. Mandal ◽  
Nicholas R. Poniatowski ◽  
Tarapada Sarkar

An understanding of the high-temperature copper oxide (cuprate) superconductors has eluded the physics community for over thirty years and represents one of the greatest unsolved problems in condensed matter physics. Particularly enigmatic is the normal state from which superconductivity emerges, so much so that this phase has been dubbed a “strange metal.” In this article, we review recent research into this strange metallic state as realized in the electron-doped cuprates with a focus on their transport properties. The electron-doped compounds differ in several ways from their more thoroughly studied hole-doped counterparts, and understanding these asymmetries of the phase diagram may prove crucial to developing a final theory of the cuprates. Most of the experimental results discussed in this review have yet to be explained and remain an outstanding challenge for theory.


2017 ◽  
Vol 31 (18) ◽  
pp. 1750204 ◽  
Author(s):  
Yunxue Teng ◽  
He Gao ◽  
Chunsheng Ma ◽  
Feng Yuan ◽  
Huaisong Zhao

There is a long-standing issue that the optical conductivity in normal-state of cuprate superconductors deviates the conventional Drude type marked by [Formula: see text] dependence, exhibiting two main components from underdoping to overdoping, a narrow band peaked around zero energy and a broadband centered in the mid-infrared region called mid-infrared band. Within the renormalized t-J model and self-consistent mean field theory, we discuss the doping and energy dependence of optical conductivity in cuprate superconductors. Our results show that the appearance of the pseudogap in normal state is responsible for anomalous optical conductivity, giving rise to the mid-infrared band. In particular, in analogy to the doping dependence of pseudogap, optical conductivity is also strongly doping dependent. By increasing the doping concentration, the spectral weight of the optical conductivity suppressed strongly in underdoped region increases quickly, and the peak position of the mid-infrared band moves towards to the lower energy region, then incorporates into the narrow band centered in zero energy in the heavily overdoped region.


2015 ◽  
Vol 29 (16) ◽  
pp. 1530009 ◽  
Author(s):  
Shiping Feng ◽  
Yu Lan ◽  
Huaisong Zhao ◽  
Lülin Kuang ◽  
Ling Qin ◽  
...  

Superconductivity in cuprate superconductors occurs upon charge-carrier doping Mott insulators, where a central question is what mechanism causes the loss of electrical resistance below the superconducting (SC) transition temperature? In this paper, we attempt to summarize the basic idea of the kinetic-energy-driven SC mechanism in the description of superconductivity in cuprate superconductors. The mechanism of the kinetic-energy-driven superconductivity is purely electronic without phonons, where the charge-carrier pairing interaction in the particle–particle channel arises directly from the kinetic energy by the exchange of spin excitations in the higher powers of the doping concentration. This kinetic-energy-driven d-wave SC-state is controlled by both the SC gap and quasiparticle coherence, which leads to that the maximal SC transition temperature occurs around the optimal doping, and then decreases in both the underdoped and overdoped regimes. In particular, the same charge-carrier interaction mediated by spin excitations that induces the SC-state in the particle–particle channel also generates the normal-state pseudogap state in the particle–hole channel. The normal-state pseudogap crossover temperature is much larger than the SC transition temperature in the underdoped and optimally doped regimes, and then monotonically decreases upon the increase of doping, eventually disappearing together with superconductivity at the end of the SC dome. This kinetic-energy-driven SC mechanism also indicates that the strong electron correlation favors superconductivity, since the main ingredient is identified into a charge-carrier pairing mechanism not from the external degree of freedom such as the phonon but rather solely from the internal spin degree of freedom of the electron. The typical properties of cuprate superconductors discussed within the framework of the kinetic-energy-driven SC mechanism are also reviewed.


1880 ◽  
Vol 26 (113) ◽  
pp. 55
Author(s):  
M. Ernest Chambard

This case shows some features common to the foregoing one, and evidently belongs to the same class. It is that of a young woman, 23 years old, who showed no hysterical tendency till the age of 20, when she received a severe mental shock by being witness to an attack of suicidal mania on the part of her mother, who was removed to the St. Anne Asylum. From that time she became triste, and complained of epigastric sensations. The developed attacks did not occur till three years later. She was a well-developed, chlorotic girl, subject to attacks of vomiting and precordial pain; ordinarily placid, she was yet emotional, but not delirious or excitable. She constantly dwelt on her mother's madness, and the scene she had then witnessed played a large part in her somnambulic state. She had no anaesthesia or analgesia; no ovarian tenderness or neuralgia. The somnambulic state was of two forms—the one simple, quiet sleep; the other accompanied by various nervous disturbances and by talking. They occurred spontaneously, and could also be provoked by pressure on the ovarian region, by closing the eyelids, &c, and she described their onset as accompanied by a sensation ot some kind of a ball rising from the lower part of the abdomen to the throat and stifling her. Then she passed into deep sleep, in which she could be made to converse, to answer questions slowly, performing voluntary actions, but with diminished sensibility. The return to the normal state was as abrupt as the lapse from it, and either occurred spontaneously or by opening her eyes, blowing on the neck. After the attack she was quiet; complained of pain in the head and limbs, and appeared fatigued, retaining no recollection of what she had passed through or done whilst in the hypnotic condition; a loss of memory that held also for the events immediately preceding her entrance into that state. Sometimes she was much surprised on waking not to find the tonic which she had drunk during the attack, and sharply accused the bystanders of having robbed her of it. Sometimes she was astonished to find herself sitting in a chair at some distance from the bed. The other kind of seizure took the form of delirium, in which she would hold conversations with imaginary individuals, and enact scenes she had passed through previously. By simply suggesting topics to her when in this state, anyone could start a long attack of this sort. It seems that every vivid moral impression, or even intellectual fatigue would give rise to a somnambulistic attack. Once the admission of an insane patient into the ward affected her so much, apparently by calling up the recollection of her mother's attack, that a few hours afterwards, whilst seated with her companions trying to work, but unable to do so, she suddenly closed her eyes, fell into a lethargic state lasting a quarter of an hour. An attack could also be induced by wearying her with conversation and questionings, as well as by various mechanical and sensorial excitations, as pressure on the ovarian region, a bright light, the “magnetic forms” of Braid—magnetism itself. M. Chambard adds some interesting comments.


2002 ◽  
Vol 16 (11n12) ◽  
pp. 1713-1719 ◽  
Author(s):  
M. FILLIPPI ◽  
N. L. SAINI ◽  
H. OYANAGI ◽  
A. BIANCONI

We report local structure of Nb3Ge intermetallic superconductor by Ge K-edge extended X-ray absorption fine structure (EXAFS) measurements performed in the temperature range of 6–300 K, with an emphasis to determine the local and instantaneous atomic displacements across the superconducting transition temperature T c . We find that the temperature dependent correlated Debye–Waller factor of the Ge-Nb bonds shows a drop at the T c while cooling the sample, similar to the one observed in the high-T c cuprate superconductors. The results provide a clear indication of an intimacy between the local atomic displacements and the short coherence superconductivity, and suggests that local electron-lattice interaction should be considered to explain the high-T c superconductivity in these materials.


2020 ◽  
pp. 2150034
Author(s):  
Ling Qin ◽  
Yiqun Liu ◽  
Shiping Feng

The doping dependence of the thermopower of cuprate superconductors in the normal-state is studied within the [Formula: see text]–[Formula: see text] model. It is shown that with a proper modification of the bare electron dispersion in the [Formula: see text]–[Formula: see text] model, the experimental results of the doping dependence of the normal-state thermopower are qualitatively reproduced. In particular, the theory shows that a pseudogap-generated split of the van Hove peak in the density of states appears in the underdoped and optimally doped regimes, however, this split is absent from the overdoped regime. Concomitantly, the strong asymmetry of the spectral conductivity near the electron Fermi surface emerges, where the peak in the spectral conductivity appears always below the electron Fermi surface in the underdoped and optimally doped regimes, while it appears above the electron Fermi surface in the overdoped regime. This strong asymmetry of the spectral conductivity leads to the unusual behaviors of the normal-state thermopower from the underdoped regime to the overdoped regime.


1999 ◽  
Vol 13 (27) ◽  
pp. 3205-3217 ◽  
Author(s):  
M. A. MOJUMDER

A study of experimental results on various parameters of underdoped cuprates in the normal state combined with analytic calculation of Hall parameters assuming a two-channel Kondo model for the system leads to the conclusion that the spin and charge pseudogaps are, respectively, a Kondo hybridisation gap and an incipient d-wave "superconducting" gap. The former occurs due to resonant scattering of doped holes by the magnetic Cu 2+ ions while the latter occurs due to incoherent Cooper pairing of Kondo-compensated quasi-itinerant Cu d-orbitals via exchange of spin excitations. We comment on the essential similarity of the high-T c and heavy fermion superconductors and a certain crossover at lower temperatures from the two-channel to the one-channel Kondo model. An expression has been derived for the Kondo contribution to the spectral function of the charge pseudogap. We believe this work unravels the long-standing conundrum of the high-T c cuprates.


2015 ◽  
Vol 8 (2) ◽  
pp. 2084-2093 ◽  
Author(s):  
PROLOY TARAN DAS ◽  
Arun Kumar Nigam ◽  
Tapan Kumar Nath

Nano-dimensional effects on electronic-, magneto-transport properties of granular ferromagnetic insulating (FMI) Pr0.8Sr0.2MnO3 (PSMO) manganite (down to 40 nm) have been investigated in details. From the electronic and magnetic transport properties, a metallic state has been observed in grain size modulation by suppressing the ferromagnetic insulating state of PSMO bulk system. A distinct metal-insulator transition (MIT) temperature around 150 K has been observed in all nanometric samples. The observed insulator to metallic transition with size reduction can be explained with surface polaron breaking model, originates due to enhanced grain surface disorder. This proposed phenomenological polaronic model plays a significant role to understand the polaronic destabilization process on the grain surface regime of these phase separated nano-mangnatie systems. Temperature dependent resistivity and magnetoresistance data in presence of external magnetic fields are investigated in details with various compatible models.


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