Partial Disorder in an Ising-Spin Kondo Lattice Model on a Triangular Lattice

Ishizuka, Hiroaki; Motome, Yukitoshi

doi:10.1103/physrevlett.108.257205

Cited by 34 publications

(39 citation statements)

References 22 publications

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“…We compare the ground state energy of the two-sublattice stripe phase and three-sublattice ferrimagnetic phase that appeared in our previous study [15], in addition to the ferromagnetic phase. The results at J ¼ 2 are shown in Fig.…”

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confidence: 97%

“…1 at low temperature T ! 0, respectively, [15,18,19]. Figure 4 shows the MC results at J ¼ 2 and J 0 ¼ 0:05 in the slightly electron doped region to n ¼ 1=3 [see also Fig.…”

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confidence: 99%

“…1. The transition at T KT is considered a Kosterlitz-Thouless type with the growth of quasilong-range order [15]. On the other hand, the phase transition at T c is a three-sublattice ferrimagnetic ordering.…”

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Dirac Half-Metal in a Triangular Ferrimagnet

Ishizuka

Motome

2012

Phys. Rev. Lett.

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An idea is proposed for realizing a fully spin-polarized Dirac semimetal in frustrated itinerant magnets. We show that itinerant electrons on a triangular lattice exhibit the Dirac cone dispersion with half-metallic behavior in the presence of a three-sublattice ferrimagnetic order. The Dirac nodes have the same structure as those of graphene. By variational calculation and Monte Carlo simulation, we demonstrate that the ferrimagnetic order with the Dirac node spontaneously emerges in a simple Kondo lattice model with Ising anisotropy. The realization will be beneficial for spintronics as a candidate for a spin-current generator.

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confidence: 97%

“…1 at low temperature T ! 0, respectively, [15,18,19]. Figure 4 shows the MC results at J ¼ 2 and J 0 ¼ 0:05 in the slightly electron doped region to n ¼ 1=3 [see also Fig.…”

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Dirac Half-Metal in a Triangular Ferrimagnet

Ishizuka

Motome

2012

Phys. Rev. Lett.

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“…Similar attempts were made for an effective pseudospin model, 11,12) the Kondo necklace model, 13-15) the Kondo lattice model, 14,16) and the periodic Anderson model 17,18) on frustrated lattice structures. However, the obtained PD states have been all insulating thus far, although metallic PD states are experimentally observed.…”

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Partial Disorder and Metal–Insulator Transition in the Periodic Anderson Model on a Triangular Lattice

2012

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The ground state of the periodic Anderson model on a triangular lattice is systematically investigated by mean-field approximation. We found that the model exhibits two different types of partially disordered states: one is at half filling and the other is at other commensurate fillings. In the latter case, the kinetic energy is lowered by forming an extensive network involving both magnetic and nonmagnetic sites, in sharp contrast to the former case in which nonmagnetic sites are rather isolated. This spatially extended nature of nonmagnetic sites yields a metallic partially disordered state by hole doping. We discuss the mechanism of the metal-insulator transition by the change in electronic structure.KEYWORDS: periodic Anderson model, geometrical frustration, triangular lattice, partial disorder, metal-insulator transitionGeometrical frustration is the conflict of competing interactions originating from the structure of the underlying lattice.1,2) The competition leads to degeneracy in low energy states, which is the source of fascinating phenomena, such as unusual orderings and exotic ground states. One of the peculiar orderings under geometrical frustration is a partial disorder (PD), which is characterized by the coexistence of magnetic order and paramagnetic or nonmagnetic sites. This offers an intriguing example of selforganization to relieve geometrical frustration.PD was first theoretically proposed in the localized Ising spin model on a triangular lattice, 3) and later experimentally observed in d-electron compounds. 4,5) In localized spin systems, PD is mainly driven by the entropic effect, and hence it is stable only at finite temperatures. On the other hand, a metallic PD was also found in some f -and d-electron compounds. [6][7][8] In stark contrast to the PD states in insulating spin systems, the metallic PD states persist down to the lowest temperature, which suggests that itinerant electrons play a key role in stabilizing the PD states. In particular, in the f -electron compounds where itinerant electrons are coupled with localized f moments, the Kondo singlet formation 9,10) is expected to be relevant to the vanishment of moments at nonmagnetic sites. In spite of extensive studies, the stabilization mechanism and the nature of these metallic PD states are not fully understood yet.In the present study, we theoretically examine the possibility of PD in itinerant electron systems by focusing on the role of coupling between itinerant and localized electrons. Similar attempts were made for an effective pseudospin model, 11,12) the Kondo necklace model, 13-15) the Kondo lattice model, 14,16) and the periodic Anderson model 17,18) on frustrated lattice structures. However, the obtained PD states have been all insulating thus far, although metallic PD states are experimentally observed. It is highly desired to establish a theory to describe metallic PD states not only for understanding the experimental results but also for paving the way to explore unusual magnetotransport properties associated with t...

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“…Such a reentrant phenomenon was experimentally confirmed 2 , and theoretically investigated with different approaches 1,[3][4][5][6][7][8] . In the past decades, systematic investigations on the partially disordered phase in both classical and quantum systems at finite temperatures were performed theoretically 1,4,5,[9][10][11][12][13][14][15] and experimentally [16][17][18][19][20][21] . It has been widely recognized that the partially disordered phase is driven by the thermal entropy, in which the disordered part behaves like a "perfect" paramagnet.…”

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Reentrance of the topological phase in a spin-1 frustrated Heisenberg chain

et al. 2020

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For the Haldane phase, the magnetic field usually tends to break the symmetry and drives the system into a topologically trivial phase. Here, we report a novel reentrance of the Haldane phase at zero temperature in the spin-1 antiferromagnetic Heisenberg model on sawtooth chain. A partial Haldane phase is induced by the magnetic field, which is the combination of the Haldane state in one sublattice and a ferromagnetically ordered state in the other sublattice. Such a partial topological order is a result of the zero-temperature entropy due to quantum fluctuations caused by geometrical frustration.Introduction. -Frustration incorporating with strong correlations usually leads to exotic quantum phenomena. A typical example in statistical physics is the reentrant phenomena, where a sequence of phase transitions, such as A-B-A-B by lowering temperature may happen, where A and B denote ordered and disordered phases, respectively. Taking the Ising model on kagomé lattice with nearest and next-nearest neighboring interactions as an example, one may find that upon lowering temperature, the system passes through four phases, a paramagnetic phase, a magnetically-ordered phase, a reentrant paramagnetic phase, and a ferromagnetic phase 1 . Such a reentrant phenomenon was experimentally confirmed 2 , and theoretically investigated with different approaches 1,3-8 . In the past decades, systematic investigations on the partially disordered phase in both classical and quantum systems at finite temperatures were performed theoretically 1,4,5,[9][10][11][12][13][14][15] and experimentally [16][17][18][19][20][21] . It has been widely recognized that the partially disordered phase is driven by the thermal entropy, in which the disordered part behaves like a "perfect" paramagnet. The reentrant phenomena can be viewed as the order-bydisorder effect 22 , which is driven by thermal fluctuations and entropy.Recently, the interests on the reentrant phenomena were renewed. The order-by-disorder effects were investigated theoretically 23-26 and experimentally 27,28 . For the spin-1/2 Heisenberg antiferromagnet on the √ 3 × √ 3disordered triangular lattice 26 , a partially disordered ground state in the weakly frustrated regime was reported. The spins on the honeycomb sublattice form a 180 • Néel order, and spins at the hexagon center sites are in a disordered state. This work is aimed at explaining the spin-liquid behaviors of LiZn 2 M o 3 O 8 29 , and shows that a partially disordered phase can be the ground state of a simple quantum isotropic Heisenberg antiferromagnet. Comparing with the classical systems, the disordered subsystem is a short range ferromagnetically correlated state instead of a paramagnet, and the mechanism is owning to the zero-point quantum fluctuations instead of the thermal ones. Furthermore, previous works 1 J 2 J : Sublattice A : Sublattice B FIG. 1. (Color online) Sawtooth chain lattice with two sublattice A and B. Two exchange interactions J1 and J2 are indicated by black and green lines, respectively.show that ...

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Partial Disorder in an Ising-Spin Kondo Lattice Model on a Triangular Lattice

Cited by 34 publications

References 22 publications

Dirac Half-Metal in a Triangular Ferrimagnet

Dirac Half-Metal in a Triangular Ferrimagnet

Partial Disorder and Metal–Insulator Transition in the Periodic Anderson Model on a Triangular Lattice

Reentrance of the topological phase in a spin-1 frustrated Heisenberg chain

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