Bosonic mean-field theory of quantum Heisenberg spin systems: Bose condensation and magnetic order

Sarker, Sanjoy K.; Jayaprakash, C.; Krishnamurthy, H. R.; Ma, Michael

doi:10.1103/physrevb.40.5028

Cited by 142 publications

(131 citation statements)

References 14 publications

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“…So, a rigorous way to apply MFA with a proper account of the projected character of HO is to use the projection technique as discussed above. The self-energy contribution (15) in the second order of the kinematic interaction is considered in [36] while it is omitted in [37]. As discussed in [36,39], it mediates the spin-fluctuation pairing and results in finite life-time effects for the quasiparticle spectrum giving rise to an incoherent contribution to the single-particle density of states.…”

Section: Self-consistent Equationsmentioning

confidence: 99%

SUPERCONDUCTIVITY IN THE t-J MODEL

Plakida¹

2002

Condens. Matter Phys.

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A comparison of microscopic theories for superconductivity in the limit of strong electron correlations is presented. We consider the results for the two-dimensional t-J model obtained within a projection technique for the Green functions in terms of the Hubbard operators and a slave-fermion representation for the RVB state. It is argued that the latter approach resulting in an odd-symmetry p-wave pairing for fermions is inadequate.

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Section: Self-consistent Equationsmentioning

confidence: 99%

SUPERCONDUCTIVITY IN THE t-J MODEL

Plakida¹

2002

Condens. Matter Phys.

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confidence: 99%

“…The interplay of interaction, disorder and kinetic energy leads to the ground states that can be a superfluid, a Bose glass, a Mott insulator or a supersolid [5][6][7][8][9][10][11]. In the context of spin models too, the Schwinger boson mean-field theories provide a useful description of magnetism in the bosonic language [12][13][14][15].Over the last decade, bosons have also been used in the context of quantum magnetism to describe the magnetization process of gapped systems with a singlet ground state such as spin ladders, the triplets induced by the magnetic being treated as hard-core bosons. These bosons may condense, leading to the ordering of the transverse component of the spins, but they might as well undergo a superfluid-insulator transition, leading to magnetization plateaux [16].…”

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confidence: 99%

Absence of Single-Particle Bose-Einstein Condensation at Low Densities for Bosons with Correlated Hopping

2005

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Motivated by the physics of mobile triplets in frustrated quantum magnets, the properties of a two dimensional model of bosons with correlated-hopping are investigated. A mean-field analysis reveals the presence of a pairing phase without single particle Bose-Einstein condensation (BEC) at low densities for sufficiently strong correlated-hopping, and of an Ising quantum phase transition towards a BEC phase at larger density. The physical arguments supporting the mean-field results and their implications for bosonic and quantum spin systems are discussed. [4]. The interplay of interaction, disorder and kinetic energy leads to the ground states that can be a superfluid, a Bose glass, a Mott insulator or a supersolid [5][6][7][8][9][10][11]. In the context of spin models too, the Schwinger boson mean-field theories provide a useful description of magnetism in the bosonic language [12][13][14][15].Over the last decade, bosons have also been used in the context of quantum magnetism to describe the magnetization process of gapped systems with a singlet ground state such as spin ladders, the triplets induced by the magnetic being treated as hard-core bosons. These bosons may condense, leading to the ordering of the transverse component of the spins, but they might as well undergo a superfluid-insulator transition, leading to magnetization plateaux [16]. For pure SU(2) interactions, and without disorder, the common belief is that the only alternative, not realized so far in quantum magnets, is a supersolid, i.e. a coexistence of these phases.In this paper, we propose that there is another possibility, namely a pairing phase without single particle Bose condensation. Our starting point is the observation that the effective bosonic model of a frustrated quantum magnet such as SrCu 2 (BO 3 ) 2 [17] contains, in addition to the usual kinetic and potential terms, a correlated-hopping term where a boson can hop only if there is another boson nearby, and that this term can be the dominant source of kinetic energy in geometries such as the orthogonal dimer model realized in SrCu 2 (BO 3 ) 2 [18,19]. While the possibility of bound state formation was already pointed out in that context, the consequences of the presence of such a term on the phase diagram at finite densities have not been worked out yet.For clarity, we concentrate in this paper on a minimal version of the model, but we have checked that the −t −t' FIG. 1: The diagonal bonds (−t′ ) denote a correlated-hopping process, and the nearest neighboring bonds denote the single particle hopping (−t).conclusions apply to the more realistic model derived for SrCu 2 (BO 3 ) 2 [20]. This model is defined on a square lattice by the Hamiltonianwhere b † r , b r are boson operators and n r = b † r b r . t and t ′ are the measures of single particle and correlated-hopping respectively. A hard core constraint that excludes multiple occupancy should in principle be included. However, we will concentrate on the low density limit, where this constraint is expected to be irrelevant. S...

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“…It can produce spin liquid phase and spin gap close to the ground state as well as the phases with long-range correlation. 15,16,17,18 In Schwinger boson representation, one can introduce two boson operators a and b to represent a spin operator S m :…”

Section: Model Hamiltonian and Schwinger Boson Mean-field Theorymentioning

confidence: 99%

Spin and orbital valence bond solids in a one-dimensional spin-orbital system: Schwinger boson mean-field theory

Shen

2005

Phys. Rev. B

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A generalized one-dimensional SU (2) × SU (2) spin-orbital model is studied by Schwinger boson mean-field theory (SBMFT). We explore mainly the dimer phases and clarify how to capture properly the low temperature properties of such a system by SBMFT. The phase diagrams are exemplified. The three dimer phases, orbital valence bond solid (OVB) state, spin valence bond solid (SVB) state and spin-orbital valence bond solid (SOVB) state, are found to be favored in respectively proper parameter regions, and they can be characterized by the static spin and pseudospin susceptibilities calculated in SBMFT scheme. The result reveals that the spin-orbit coupling of SU (2) × SU (2) type serves as both the spin-Peierls and orbital-Peierles mechanisms that responsible for the spin-singlet and orbital-singlet formations respectively.

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Bosonic mean-field theory of quantum Heisenberg spin systems: Bose condensation and magnetic order

Cited by 142 publications

References 14 publications

SUPERCONDUCTIVITY IN THE t-J MODEL

SUPERCONDUCTIVITY IN THE t-J MODEL

Absence of Single-Particle Bose-Einstein Condensation at Low Densities for Bosons with Correlated Hopping

Spin and orbital valence bond solids in a one-dimensional spin-orbital system: Schwinger boson mean-field theory

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