A NUMERICAL AND ANALYTICAL STUDY OF TWO HOLES DOPED INTO THE 2D t–J MODEL

Chernyshev, A. L.; Leung, Pak Wo; Gooding, R. J.

doi:10.1016/s0022-3697(98)00112-7

Cited by 7 publications

(8 citation statements)

References 86 publications

(247 reference statements)

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“…5A) ( 6 ). This disagrees with the d-wave symmetry of a Cooper pair in doped cuprates ( 42 ). A Cooper pair is formed by two holons, whereas an exciton is formed by a doublon and a holon.…”

Section: Discussioncontrasting

confidence: 75%

Doublon-holon pairing mechanism via exchange interaction in two-dimensional cuprate Mott insulators

et al. 2019

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Coupling of charge and spin degrees of freedom is a critical feature of correlated electron oxides, as represented by the spin-related mechanism of a Cooper pair under high-Tc superconductivity. A doublon-holon pair generated on an antiferromagnetic spin background is also predicted to attract each other via the spin-spin interaction J, similar to a Cooper pair, while its evidence is difficult to obtain experimentally. Here, we investigate such an excitonic effect by electroreflectance spectroscopy using terahertz electric field pulses in undoped cuprates: Nd2CuO4, Sr2CuO2Cl2, and La2CuO4. Analyses of the spectral changes of reflectivity under electric fields reveal that the splitting of odd-parity and even-parity excitons, a measure of doublon-holon binding energy, increases with J. This trend is reproduced by t-J–type model calculations, providing strong evidence of the spin-related doublon-holon pairing. Agreement with the calculations supports the s-wave symmetry of the doublon-holon pair in contrast to the d-wave Cooper pair in doped cuprates.

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“…5A) ( 6 ). This disagrees with the d-wave symmetry of a Cooper pair in doped cuprates ( 42 ). A Cooper pair is formed by two holons, whereas an exciton is formed by a doublon and a holon.…”

Section: Discussioncontrasting

confidence: 75%

Doublon-holon pairing mechanism via exchange interaction in two-dimensional cuprate Mott insulators

et al. 2019

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“…In the BCS theory, two electrons injected into a Fermi liquid can always form a Cooper pair under an arbitrarily weak attractive interaction. Ever since the discovery of the high- T c cuprates, a great effort has been devoted to finding the responsible pairing glue, which is widely attributed to the superexchange interaction 1 2 3 4 5 6 .…”

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confidence: 99%

Nature of strong hole pairing in doped Mott antiferromagnets

Zhu

Jiang

Weng

2014

Sci Rep

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Cooper pairing instability in a Fermi liquid is well understood by the BCS theory, but pairing mechanism for doped Mott insulators still remains elusive. Previously it has been shown by density matrix renormalization group (DMRG) method that a single doped hole is always self-localized due to the quantum destructive interference of the phase string signs hidden in the t-J ladders. Here we report a DMRG investigation of hole binding in the same model, where a novel pairing-glue scheme beyond the BCS realm is discovered. Specifically, we show that, in addition to spin pairing due to superexchange interaction, the strong frustration of the phase string signs on the kinetic energy gets effectively removed by pairing the charges, which results in strong binding of two holes. By contrast, if the phase string signs are “switched off” artificially, the pairing strength diminishes significantly even if the superexchange coupling remains the same. In the latter, unpaired holes behave like coherent quasiparticles with pairing drastically weakened, whose sole origin may be attributed to the resonating-valence-bond (RVB) pairing of spins. Such non-BCS pairing mechanism is therefore beyond the RVB picture and may shed important light on the high-Tc cuprate superconductors.

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“…Such a two-hole t-J model on a 32-site cluster has recently been solved using exact diagonalization. 6,7 In this study we use the same lowest-energy d-wave states at different J/t as in Ref. 7.…”

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confidence: 99%

Signatures of a staggered-flux phase in thet−Jmodel with two holes on a 32-site lattice

Leung

2000

Phys. Rev. B

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We study the relevance of the staggered-flux phase in the t-J model using a system with two holes on a 32-site lattice with periodic boundary conditions. We find a staggered-flux pattern in the current-current correlation in the lowest energy d-wave state where there is mutual attraction between the holes. This staggered correlation decays faster with distance when the hole binding becomes stronger. This is in complete agreement with a recent study by Ivanov, Lee, and Wen ͓Phys. Rev. Lett. 84, 3958 ͑2000͔͒ based on the SU͑2͒ theory, and strongly suggests that the staggered-flux phase is a key ingredient in the t-J model. We further show that this staggered-flux pattern does not exist in a state where the holes repel each other. Correlations of the chirality operator S 1 •(S 2 ϫS 3 ) show that the staggered pattern of the chirality is closely tied to the holes.The t-J model is one of the most important microscopic models in the study of high-temperature superconductivity. It describes a doped CuO 2 plane as a system of holes ͑or Zhang-Rice singlets 1 ͒ moving in a spin background described by the antiferromagnetic Heisenberg model. The Hamiltonian iswhere c i † and c i are the projected fermion operators, and n i ϵc i † c i is the fermion number operator. Understanding the properties of this model is a major challenge in the theoretical study of high-temperature superconductivity. In spite of the simple form of H, solving the t-J model is nontrivial due to the strong interaction of the fermion objects. Meanfield theory solutions to the model often involve a fictitious statistical flux. 2 The flux pattern in these ''flux phases'' can be uniform or staggered. In particular, it has been proposed that the staggered-flux phase in the t-J model might lower the energy of the system and become the ground state at parameters relevant to experimental systems. 3 However, being an abstract mathematical quantity, it is difficult to find a suitable signature for the flux. Consequently, independent confirmation of the existence of flux phases by numerical or experimental studies is difficult. A previous attempt to search for flux phases using exact diagonalization on small clusters 4 has been either negative or inconclusive.As pointed out by Ivanov, Lee, and Wen, 5 in the case of the doped t-J model a signature for the staggered-flux phase can be found in the current-current correlation. Using a Gutzwiller-projected d-wave pairing wave function, they found such a pattern in the current correlation; namely, the hole current goes around the elementary square plaquettes in the counterclockwise and clockwise directions, suggestive of positive and negative fluxes through the plaquettes in a staggered manner. They explained this observation by showing that the Gutzwiller-projected d-wave pairing wave function is equivalent to the SU͑2͒ projected staggered-flux wave function. Although this result shows that the concept of a staggered-flux phase is relevant in the projected d-wave pairing wave function, it does not answer the question ...

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A NUMERICAL AND ANALYTICAL STUDY OF TWO HOLES DOPED INTO THE 2D t–J MODEL

Cited by 7 publications

References 86 publications

Doublon-holon pairing mechanism via exchange interaction in two-dimensional cuprate Mott insulators

Doublon-holon pairing mechanism via exchange interaction in two-dimensional cuprate Mott insulators

Nature of strong hole pairing in doped Mott antiferromagnets

Signatures of a staggered-flux phase in thet−Jmodel with two holes on a 32-site lattice

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