Fizika Nizkikh Temperatur: Volume 44, Number 2 (February 2018), p. 173-184 ( to contents , go back )
Hierarchy of low-energy models of the electronic structure of cuprate HTSCs: the role of long-range spin-correlated hoppings
V.V. Val’kov1, V.A. Mitskan1,2, D.M. Dzebisashvili1,2, and A.F. Barabanov3
1Kirensky Institute of Physics, 660036 Krasnoyarsk, Russian Federation
2Сибирский государственный университет науки и технологий им. М.Ф. Решетнева г. Красноярск, 660037, Россия
3L.F. Vereshchagin Institute for High-Pressure Physics, RAN, Troitsk 142190, Russia
Received June 7, 2017
It is shown that for the three-band Emery p–d-model that reflects the real structure of the CuO2-plane of high-temperature superconductors, in the regime of strong electron correlations it is possible to carry out a sequence of reductions to the effective models reproducing low-energy features of elementary excitations spectrum and revealing the spin-polaron nature of the Fermi quasiparticles. The first reduction leads to the spin-fermion model in which the subsystem of spin moments, coupled by exchange interaction and localized on copper ions, strongly interacts with oxygen holes. The second reduction is connected with the transformation from the spin-fermion model to the φ–d-exchange model. An important feature of this transformation is the large energy of the φ–d-exchange coupling, which leads to the formation of spin polarons. The use of this fact allows us to carry out the third reduction, as a result of which a t̃ - J̃ * - I -model arises. Its distinctive feature is related to the much greater importance of spin-correlated hoppings as compared to the role of such processes in the commonly used t-J * -model derived from the Hubbard model. Based on the comparative analysis of the spectrum of Fermi excitations calculated for the obtained effective models of the CuO2-plane of high-temperature superconductors, the important role of the usually discarded long-range spin-correlated hoppings is determined.
PACS: 74.20.–z Theories and models of superconducting state;
Key words: high-temperature superconductors, spin polaron, low-energy model of the electronic structure of cuprates.
Published online: December 26, 2017