Phase separation in a<i>t</i>-<i>J</i>model

Marder, Michael; Papanicolaou, N.; Psaltakis, G.C.

doi:10.1103/physrevb.41.6920

Cited by 114 publications

(45 citation statements)

References 16 publications

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“…This result implies instability to a spiral state, while the system can further lower its energy by phase separating. 7,40 Due to the variational nature of our calculation, it is guaranteed that, if the magnon energy becomes negative for J = J c (n), the ground state of the Hamiltonian H for all J < J c (n) is not the half metallic state |F . The phase diagrams of Fig.…”

Section: Numerical Resultsmentioning

confidence: 99%

Three-body correlation effects on the spin dynamics of double-exchange ferromagnets

2006

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We present a variational calculation of the spin wave excitation spectrum of double-exchange ferromagnets in different dimensions. Our theory recovers the Random Phase approximation and 1/S expansion results as limiting cases and can be used to study the intermediate exchange coupling and electron concentration regime relevant to the manganites. In particular, we treat exactly the long range three-body correlations between a Fermi sea electron-hole pair and a magnon excitation and show that they strongly affect the spin dynamics in the parameter range relevant to experiments in the manganites. The manifestations of these correlations are many-fold. We demonstrate that they significantly change the ferromagnetic phase boundary. In addition to a decrease in the magnon stiffness, we obtain an instability of the ferromagnetic state against spin wave excitations close to the Brillouin zone boundary. Within a range of intermediate concentrations, we find a strong softening of the spin wave dispersion as compared to the Heisenberg ferromagnet with the same stiffness, which changes into hardening for other concentrations. We discuss the relevance of these results to experiments in colossal magnetoresistance ferromagnets.

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Section: Numerical Resultsmentioning

confidence: 99%

Three-body correlation effects on the spin dynamics of double-exchange ferromagnets

2006

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“…If the holes were neutral the system would separate into a hole-free antiferromagnetic phase and a hole-rich (magnetically disordered or possibly ferromagnetic) phase, in which the holes are mobile and the cost in exchange energy is less than the gain in kinetic energy. [25][26][27] In practice the holes are charged, but macroscopic phase separation can take place whenever the dopants are mobile, as in oxygen-doped and photo-doped materials. We have reviewed the experimental evidence for this behavior elsewhere.…”

Section: Topological Dopingmentioning

confidence: 99%

Local electronic structure and high temperature superconductivity

Emery¹,

Kivelson²

1999

AIP Conference Proceedings

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Abstract.It is argued that a new mechanism and many-body theory of superconductivity are required for doped correlated insulators. Here we review the essential features of and the experimental support for such a theory, in which the physics is driven by the kinetic energy. I INTRODUCTIONHigh temperature superconductivity [1] is obtained by adding charge carriers into a highly-correlated antiferromagnetic insulating state. Despite the fact that there is a large "Fermi surface" containing all of the pre-existing holes and the doped holes, [2] it is impossible to understand the behavior of the system and, in particular, the origin of high temperature superconductivity unless the nature of the dopedinsulating state is incorporated into the theory. In particular, the Fermi liquid theory of the normal state and the BCS theory of the superconducting state, which are so successful for conventional metals, were not designed for doped insulators, and they do not apply to the high temperature superconductors. (Section II.) Consequently it is necessary to develop a new mechanism and many-body theory of high temperature superconductivity.In our view, the physics of the insulator and the doped insulator, including antiferromagnetism and superconductivity, is driven by a lowering of the zeropoint kinetic energy.[3] This is well known for the antiferromagnetic state but, in addition, the motion of a single hole in an antiferromagnet is frustrated because it stirs up the spins and creates strings of ferromagnetic bonds. Consequently, a finite density of holes forms self-organized structures, designed to lower the zero-point kinetic energy. This is accomplished in three stages: a) the formation of charge inhomogeneity (stripes), b) the creation of local spin pairs, and c) the establishment of a phase-coherent high-temperature superconducting state. The zero-point kinetic

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“…In the t -J model, it was rapidly realized that at large J It, the model phase separated (Refs. 105,162,163,164, and references therein). As explained before, adding a low mobility hole to the undoped system amounts to removing four antiferromagnetic links, thus increasing the energy of the system.…”

Section: Phase Separationmentioning

confidence: 96%

High Temperature Superconductors: A Review

Dagotto

1995

Recent Progress in Many-Body Theories

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Phase separation in at-Jmodel

Cited by 114 publications

References 16 publications

Three-body correlation effects on the spin dynamics of double-exchange ferromagnets

Three-body correlation effects on the spin dynamics of double-exchange ferromagnets

Local electronic structure and high temperature superconductivity

High Temperature Superconductors: A Review

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