Quantum Disordered Phase in a Doped Antiferromagnet

Kübert, C.; Muramatsu, A.

doi:10.1209/0295-5075/30/8/007

Cited by 5 publications

(6 citation statements)

References 21 publications

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“…This model is the starting point that leads to the t-J model in the limit where the exchange coupling between the dopant hole, that mainly resides on the oxygen orbitals, and the copper hole form the Zhang-Rice singlet [27]. The gradient expansion for the spin-fermion model based on the assumption of a short-range antiferromagnetic order led to an O(3) non-linear σ-model, that as a function of doping had a transition to the corresponding quantum disordered phase [49]. Hence, under the same assumption as in the present work, no hint to deconfinement of spinons was obtained.…”

Section: Discussion Of the Results And Conclusionmentioning

confidence: 99%

Massive CP1 theory from a microscopic model for doped antiferromagnets

Falb

Muramatsu

2008

Nuclear Physics B

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A path-integral for the t-J model in two dimensions is constructed based on Dirac quantization, with an action found originally by Wiegmann (Phys. Rev. Lett. 60, 821 (1988); Nucl. Phys. B323, 311 (1989)). Concentrating on the low doping limit, we assume short range antiferromagnetic order of the spin degrees of freedom. Going over to a local spin quantization axis of the dopant fermions, that follows the spin degree of freedom, staggered CP 1 fields result and the constraint against double occupancy can be resolved. The staggered CP 1 fields are split into slow and fast modes, such that after a gradient expansion, and after integrating out the fast modes and the dopant fermions, a CP 1 field-theory with a massive gauge field is obtained that describes generically incommensurate coplanar magnetic structures, as discussed previously in the context of frustrated quantum antiferromagnets. Hence, the possibility of deconfined spinons is opened by doping a collinear antiferromagnet.PACS numbers: 71.10.Fd, II. DIRAC QUANTIZATION OF THE t-J MODELWe introduce first the t-J model and its representation in terms of so-called X-operators that operate only in the subspace without doubly occupancy. After discussing shortly the algebra they fulfill, we delineate the procedure of Dirac quantization. A. The t-J model and X-operatorsThe t-J model is defined by the following Hamiltonian in second quantization:

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Section: Discussion Of the Results And Conclusionmentioning

confidence: 99%

Massive CP1 theory from a microscopic model for doped antiferromagnets

Falb

Muramatsu

2008

Nuclear Physics B

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“…[4] we get m = 3/2 and γ = 1/12 [15]. With the experimental value ρ = 1.7 · 10 −2 [16] we explicitly get δ c ∼ 4% [11]. Finally for |y| ≪ 1 the system is in the quantum critical (QC) regime which is completely determined by the critical point (δ c , T = 0) [14].…”

Section: Large-n Expansion For the Gauge Theorymentioning

confidence: 86%

“…[4] we get m = 3/2 and γ = 1/12 [15]. With the experimental value ρ = 1.7 • 10 −2 [16] we explicitly get δ c ∼ 4% [11].…”

mentioning

confidence: 77%

Gauge Theory for a Doped Antiferromagnet in a Rotating Reference-Frame

Kübert¹,

Muramatsu²

1996

Int. J. Mod. Phys. B

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We study a doped antiferromagnet (AF) using a rotating reference-frame. Whereas in the laboratory reference-frame with a globally fixed spin-quantization axis (SQA) the long-wavelength, lowenergy physics is given by the O(3) non-linear σ-model with current-current interactions between the fermionic degrees of freedom and the order-parameter field for the spin-background, an alternative description in form of an U(1) gauge theory can be derived by choosing the SQA defined by the local direction of the order-parameter field via a SU(2) rotation of the fermionic spinor. Within a large-N expansion of this U(1) gauge theory we obtain the phase diagram for the doped AF and identify the relevant terms due to doping that lead to a quantum phase transition at T = 0 from the antiferromagnetically ordered Néel phase to the quantum-disordered (QD) spin-liquid phase. Furthermore, we calculate the propagator of the corresponding U(1) gauge field, which mediates a long-range transverse interaction between the bosonic and fermionic fields. It is found that the strength of the propagator is proportional to the gap of the spin-excitations. Therefore, we expect as a consequence of this long-range interaction the formation of bound states when the spin-gap opens, i.e. in the QD spin-liquid phase. The possible bound states are spin-waves with a (spin-) gap in the excitation spectrum, spinless fermions and pairs of fermions. Thus, an alternative picture for charge-spin separation emerges, with composite charge-separated excitations. Moreover, the present treatment shows an intimate connection between the opening of the spin-gap and charge-spin separation as well as pairing.

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“…However, the most interesting and relevant situation of strongly correlated systems, where magnetic as well as charge degrees of freedom interact, was until now investigated to a much lesser extent. Apart from numerous mean-field attempts to analyze those systems, to the best knowledge of the authors only few field-theories have been derived from microscopic models so far [14][15][16][17], besides phenomenological approaches [18], where fluctuations effects are duly taken into account.…”

Section: Introductionmentioning

confidence: 99%