Local transformation of the electronic structure and generation of free carriers in cuprates and ferropnictides under heterovalent and isovalent doping

Mitsen, K. V.; Ivanenko, O. M.

doi:10.1016/j.rinp.2022.105577

Cited by 3 publications

(10 citation statements)

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“…In optimally doped cuprates in which superconductivity occurs in a percolation cluster, this effect is much weaker and is due to only a small number of remaining small clusters. Overdoped samples, in which the superconducting cluster occupies the entire CuO2 plane [13][14][15], will behave like ordinary superconductors. reverses sign in the region of maximum 𝜎 1𝑠 𝑟𝑒𝑔 ().…”

Section: Anomalous Transfer Of Spectral Weightmentioning

confidence: 99%

“…Thus, assumptions about the structure of the underdoped phase of cuprates as a medium consisting of isolated finite clusters oscillating in a certain temperature range between the superconducting and normal states make it possible to explain the main features of the optical response observed in numerous experiments. Next, within the framework of the previously proposed model [13][14][15], we consider the nature of the cluster structure of underdoped cuprates, and what mechanism of superconducting pairing allows small clusters to switch at a constant temperature between normal and superconducting states.…”

Section: Anomalous Transfer Of Spectral Weightmentioning

confidence: 99%

“…The proposed model of heterovalently doped cuprates [13][14][15] is based on the assumption of the local character of the electronic structure deformation of the crystal by the dopant ion. We consider initially undoped cuprates as charge-transfer (CT) insulators with a gap ct [38].…”

Section: The Nature Of Cluster Structure Of Underdoped Cupratesmentioning

confidence: 99%

“…We consider initially undoped cuprates as charge-transfer (CT) insulators with a gap ct [38]. The local nature of the deformation of their electronic structure is determined by the localization of the doped carrier in the immediate vicinity of the dopant due to the formation around the doped charge of a trion complex -the bound state of the doped carrier and CT excitons that arise under the influence of this charge in the surrounding CuO4 plaquettes (we called such plaquettes as CT plaquettes) [13,14]. This becomes possible if the doped charge suppresses the initial charge-transfer gap ct in neighboring CuO4 plaquettes, to a value ∆ 𝑐𝑡 ′ < ct, sufficient for the production of CT excitons in these plaquettes [13].…”

Section: The Nature Of Cluster Structure Of Underdoped Cupratesmentioning

confidence: 99%

“…We have previously shown that, due to local deformation of the electronic structure of cuprates and pnictides by impurity ions, the doping process at low concentrations (in underdoped region) is accompanied by the formation of individual clusters of a new phase with a special electronic structure [13], in which a specific mechanism of superconductivity may be realized [14]. We have shown that the positions of the superconducting domes in the phase diagrams of cuprates and pnictides coincide with the existence intervals of percolation cluster of this phase.…”

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confidence: 99%

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On the Nature of Scaling Relations in Cuprate HTSCs

Mitsen

Ivanenko

2021

Bull. Lebedev Phys. Inst.

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The nature of the normal state and the mechanism of superconductivity in HTSC cuprates remain under discussion until now. However, a number of experimental facts may be considered firmly established: 1) There is a d-wave superconducting energy gap on the 2D Fermi surface (FS) of optimally doped HTSC cuprates, with zeros in node directions [1]. 2) The transition to normal state is accompanied by the closing of the gap across parts of the FS and the formation of Fermi arcs centered at the nodes. Meanwhile, the gap in antinode directions virtually does not change across T c ("pseudogap") and closes at some temperature Т*well above T c [2,3]. 3) As the doping level is reduced, the pseudogap increases and deviates from the simple d-wave behavior [4]. In deeply underdoped samples, Cooper pairs form islands in k-space around the nodal regions [5]. 4) Above Т с , underdoped samples exhibit giant Nernst effect and anomalous diamagnetism [6,7]. Here we suggest a simple physical model of HTSC cuprates that provides explanation of the features listed above. According to this model, the unusual properties of these compounds result from their unique electronic structure favourable for the formation of diatomic negative-U centers (NUCs) and realization of an unusual mechanism of electron−electron interaction.The suggested model is based on the mechanism of the formation of NUCs in HTSCs that we proposed previously [8]. Its essence can be understood from Fig. 1a, which shows the electronic spectrum of a CuO 2 plane of an undoped HTSC. It is known that the electronic structure of the insulating phase of HTSCs in the vicinity of the Fermi energy E F is described well by the model of an insulator with a charge-transfer gap [9]. In this scheme, the energy of the lowest-lying excitation Δ сt (~2 eV) is related to the transfer of an electron from an oxygen ion to a neighboring copper ion, 3d 9 L→3d 10 L -(here, 3d 9 L denotes the state with a hole on the 3d-shall of Cu ion and a completely occupied 2p-shell of the neighboring ligand (oxygen), and 3d 10 Lis the state with a completely occupied 3d-shell of Cu and a hole on the ligand ion). Note that the Cu3d 10 L state is considerably higher in energy than Cu3d 10 L -.

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Section: Anomalous Transfer Of Spectral Weightmentioning

confidence: 99%

Section: Anomalous Transfer Of Spectral Weightmentioning

confidence: 99%