Phase Transition of the Heisenberg Antiferromagnet on the Triangular Lattice in a Magnetic Field

Kawamura, Hikaru; Miyashita, Seiji

doi:10.1143/jpsj.54.4530

Cited by 200 publications

(220 citation statements)

References 4 publications

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“…One can show that in the thermodynamic limit, the correlation function in Eq. (14) reduces to a simple power-law relation ∝ |x − x | −η , which is reflected by our data for distances |x − x | L/2.…”

Section: S ± Correlationssupporting

confidence: 69%

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Ground states of spin-12triangular antiferromagnets in a magnetic field

Chen

Jiang

et al. 2013

Phys. Rev. B

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We use a combination of numerical density matrix renormalization group (DMRG) calculations and several analytical approaches to comprehensively study a simplified model for a spatially anisotropic spin-1/2 triangular lattice Heisenberg antiferromagnet: the three-leg triangular spin tube (TST). The model is described by three Heisenberg chains, with exchange constant J, coupled antiferromagnetically with exchange constant J along the diagonals of the ladder system, with periodic boundary conditions in the shorter direction. Here we determine the full phase diagram of this model as a function of both spatial anisotropy (between the isotropic and decoupled chain limits) and magnetic field. We find a rich phase diagram, which is remarkably dominated by quantum states -the phase corresponding to the classical ground state appears only in an exceedingly small region. Among the dominant phases generated by quantum effects are commensurate and incommensurate coplanar quasi-ordered states, which appear in the vicinity of the isotropic region for most fields, and in the high field region for most anisotropies. The coplanar states, while not classical ground states, can at least be understood semiclassically. Even more strikingly, the largest region of phase space is occupied by a spin density wave phase, which has incommensurate collinear correlations along the field. This phase has no semiclassical analog, and may be ascribed to enhanced one-dimensional fluctuations due to frustration. Cutting across the phase diagram is a magnetization plateau, with a gap to all excitations and "up up down" spin order, with a quantized magnetization equal to 1/3 of the saturation value. In the TST, this plateau extends almost but not quite to the decoupled chains limit. Most of the above features are expected to carry over to the two dimensional system, which we also discuss. At low field, a dimerized phase appears, which is particular to the one dimensional nature of the TST, and which can be understood from quantum Berry phase arguments.

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Section: S ± Correlationssupporting

confidence: 69%

“…One is now able to fit the DMRG measurement of the transverse spinspin correlation function to Eqs. (13,14) to obtain the ordering wave vector and the additional fit parameter, η. A comparison is plotted in Fig.…”

Section: S ± Correlationsmentioning

confidence: 99%

Ground states of spin-12triangular antiferromagnets in a magnetic field

Chen

Jiang

et al. 2013

Phys. Rev. B

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“…For details see text. For the triangular-lattice AF, an anomalously large ground-state degeneracy exists at the classical level for h = 0, which is lifted both by fluctuations and by additional interactions [15][16][17][18]. Two cases are important: (a) "coplanar" and (b) "umbrella" states, see Fig.…”

Section: Figmentioning

confidence: 99%

Singular Field Response and Singular Screening of Vacancies in Antiferromagnets

Wollny¹,

Andrade²,

Vojta³

2012

Phys. Rev. Lett.

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For isolated vacancies in ordered local-moment antiferromagnets we show that the magnetic-field linear-response limit is generically singular: The magnetic moment associated with a vacancy in zero field is different from that in a finite field h in the limit h → 0 + . The origin is a universal and singular screening cloud, which moreover leads to perfect screening as h → 0 + for magnets which display spin-flop bulk states in the weak-field limit.Defects are ubiquitous in solids. In magnets with localized spin moments, typical classes of defects are missing or extra spins, arising, e.g., from substitutional disorder. Very often, even small concentrations of such defects produce a large magnetic response at low temperatures: Quasi-free spins cause a Curie tail in the magnetic susceptibility, which then is routinely subtracted from raw experimental data. Assuming independent defects, the amplitude of the Curie tail can be utilized to estimate the defect concentration, provided that the behavior of a single defect is known.Here we discuss the physics of isolated vacancies in antiferromagnets (AF) which display semiclassical longrange order (LRO) in the ground state [1]. In zero magnetic field, the state with a single vacancy has a finite uniform magnetic moment, m 0 , because the vacancy breaks the balance between the sublattices. For collinear magnets, m 0 is quantized to the bulk spin value, m 0 = S [2, 3], while in the non-collinear case fractional values of m 0 occur due to the local relief of frustration [4]. These vacancy moments are expected to show up in magnetization measurements, and they produce a low-temperature Curie contribution to the uniform susceptibility in the two-dimensional (2d) case where bulk order is prohibited by the Mermin-Wagner theorem [3][4][5][6][7].In this paper we show that, in an applied field h, nontrivial screening of the vacancy moment occurs, such that the linear-response limit h → 0 + is singular for a magnet with a single vacancy, Fig. 1: The vacancy-induced magnetization jumps discontinuously from its zero-field value m 0 to a different value m(h → 0 + ) upon applying an infinitesimal field h. Thus, measurements of the vacancy-induced moment m(h) in a finite field h cannot detect the zero-field value m 0 even for small h [8], which is of obvious relevance for any experiment trying to quantify the defect contribution to a sample's magnetization or susceptibility. Furthermore, the spin texture around the vacancy at finite h has a piece [9] which is singular as h → 0 + -in a sense made precise belowwhich screens the vacancy-induced moment perpendicular to h. For magnets which feature spin-flop states (with all spins perpendicular to h as h → 0 + ) in the absence of the vacancy, this leads to a semiclassical version of perfect screening of the vacancy moment, m(h → 0 + ) = 0.In the body of paper, we present general arguments and microscopic calculations supporting these claims. Explicit results will be given in a 1/S expansion for spin-S AFs on 2d lattices, with(1) but our results...

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“…M sat in the triangular lattice antiferromagnet [6,7]. It is a remarkably stable state known to survive significant spatial deformation of exchange integrals in both quantum (spin 1/2) and classical versions of the model [8][9][10].…”

mentioning

confidence: 99%

Half-metallic magnetization plateaux

Hao

Starykh

2013

Phys. Rev. B

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We propose a novel interaction-based route to half-metal state for interacting electrons on two-dimensional lattices. Magnetic field applied parallel to the lattice is used to tune one of the spin densities to a particular commensurate with the lattice value in which the system spontaneously `locks in' via van Hove enhanced density wave state. Electrons of opposite spin polarization retain their metallic character and provide for the half-metal state which, in addition, supports magnetization plateau in a finite interval of external magnetic field. Similar half-metal state is realized in the finite-U Hubbard model on a triangular lattice at 1/3 of the maximum magnetization.Comment: 7 pages, 8 figure

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Phase Transition of the Heisenberg Antiferromagnet on the Triangular Lattice in a Magnetic Field

Cited by 200 publications

References 4 publications

Ground states of spin-12triangular antiferromagnets in a magnetic field

Ground states of spin-12triangular antiferromagnets in a magnetic field

Singular Field Response and Singular Screening of Vacancies in Antiferromagnets

Half-metallic magnetization plateaux

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