Spin-lattice model of magnetoelectric transitions in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>RbCoBr</mml:mtext></mml:mrow><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>

Nakamura, Tota; Nishiwaki, Yasushi

doi:10.1103/physrevb.78.104422

Cited by 16 publications

(17 citation statements)

References 30 publications

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“…The algorithm was successfully applied to the theoretical analysis on the magneto-electric transitions in RbCoBr 3 . [19] The numerical results quantitatively agree with the experimental results. The estimates of the interaction parameters and proposals of new experiments were made possible.…”

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confidence: 80%

Efficient Monte Carlo Algorithm in Quasi-One-Dimensional Ising Spin Systems

Nakamura

2008

Phys. Rev. Lett.

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We have developed an efficient Monte Carlo algorithm, which accelerates slow Monte Carlo dynamics in quasi-one-dimensional Ising spin systems. The loop algorithm of the quantum Monte Carlo method is applied to the classical spin models with highly anisotropic exchange interactions. Both correlation time and real CPU time are reduced drastically. The algorithm is demonstrated in the layered triangular-lattice antiferromagnetic Ising model. We have obtained the relation between the transition temperature and the exchange interaction parameters, which modifies the result of the chain-mean-field theory. The application of the Monte Carlo (MC) method to the condensed-matter physics has been successful bridging between the experimental study and the theoretical study.[1] The simulational results are now quantitatively compared with the experimental results. We may estimate various physical parameters, predict unknown properties, and propose new experiments on real materials. However, we encounter a difficulty when we apply the MC method to the frustrated systems. The MC dynamics slows down, and it becomes very hard to reach the equilibrium states. Since frustration has been recognized to play an important role in novel effects of many materials, [2] we somehow have to overcome this difficulty to study new properties, new concepts and new function of such materials.In this Letter we consider the quasi-one-dimensional (Q1D) frustrated spin systems. The magnetic exchange interaction of this system is highly anisotropic. The interaction along the c axis is much stronger than those within the ab plane: |J c | ≫ |J ab |. The experimental realizations of this model are the ABX 3 -type compounds. [3,4,5,6,7] The lattice structure is the stacked triangular lattice with the antiferromagnetic exchange interactions. There are two reasons for the slow MC dynamics in this system. One is frustration, and the other is the long correlation length along the c axis. The single-spin-flip algorithm cannot change the states of these correlated clusters. Koseki and Matsubara [8,9,10] proposed the clusterheat-bath method, which accelerates the MC dynamics in Q1D Ising spin systems. When we update a spin state, the transfer matrix is multiplied along the c axis. This matrix operation takes a long CPU time. The possible size of simulation has been restricted to the system with |J c /J ab | = 10, 36 × 36 × 360 spins, and 2 × 10 6 MC steps. [11] Considering that the ratio |J c /J ab | in real compounds is in the order of 100, we need to develop another algorithm that improves the simulation efficiency.We notice that the similar slow-dynamic situation occurs in the quantum Monte Carlo (QMC) simulation.[12] The d-dimensional quantum system is mapped to the (d + 1)-dimensional classical system, on which the simulation is performed. The additional dimension is called the Trotter direction, and its length is called the Trotter number. The (d + 1)-dimensional classical system becomes equivalent to the original d-dimensional quantum system when the Tro...

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confidence: 80%

Efficient Monte Carlo Algorithm in Quasi-One-Dimensional Ising Spin Systems

Nakamura

2008

Phys. Rev. Lett.

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“…In the limit V = ∆ = λ = 0, Eq. (22) reduces to similar ones for bilayer graphene 24,25 . Figure 10 shows the Hall conductivity as a function of the field B for V = 0 meV.…”

Section: A Hall Conductivitymentioning

confidence: 72%

“…(15). Further, the plateaux in bilayer MoS 2 have different origin than those in bilayer graphene: the former are due to the strong SOC whereas the later result from strong interlayer coupling 24,25 . A noteworthy feature of bilayer MoS 2 is that the influence of SOC and interlayer coupling is enhanced with increasing LL index and leads to new Hall plateaux as is evident from both panels of Fig.…”

Section: A Hall Conductivitymentioning

confidence: 98%

Quantum magnetotransport in bilayer MoS2 : Influence of perpendicular electric field

et al. 2017

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We first derive the energy dispersion of bilayer MoS 2 in the presence of a perpendicular electric field E z . We show that the band gap and layer splitting can be controlled by the field E z . Away from the k point, the intrinsic SOC splitting increases in the conduction band but is weakly affected in the valence band. We then analyze the band structure in the presence of a perpendicular magnetic field B and the field E z , including spin and valley Zeeman terms, and evaluate the Hall and longitudinal conductivities. We discuss the numerical results as functions of the fields B and E z for finite temperatures. The field B gives rise to a significant spin splitting in the conduction band, to a beating in the Shubnikov-de Haas (SdH) oscillations when it's weak, and to their splitting when it's strong. The Zeeman terms and E z suppress the beating and change the positions of the beating nodes of the SdH oscillations at low B fields and enhance their splitting at high B fields. Similar beating patterns are observed in the spin and valley polarizations at low B fields. Interestingly, a 90% spin polarization and a 100% square-wave-shaped valley polarization are observed at high B fields. The Hall-plateau sequence depends on E z . These findings may be pertinent to future spintronic and valleytronic devices.Recently the MoS 2 monolayer has provided a new testbed for the study of fermion physics in reduced dimensions. Its strong intrinsic SOC and huge band gap 1 , approximately 2λ = 150 meV and 2∆ = 1.66 eV, respectively, render it pertinent to potential applications in spintronics and optoelectronics 2-5 . Due to these features, MoS 2 may be more appropriate for device applications than graphene and the conventional two-dimensional electron gas (2DEG). Other investigated properties of monlayer MoS 2 are magnetocapacitance 6 , spinand valley-dependent magnetooptical spectra 7-9 and an unconventional quantum Hall effect (QHE) 10 . Most recently, magnetotransport studies of monolayer MoS 2 have been carried out [11][12][13] .In addition to monolayer MoS 2 , it has been recently realized that bilayer MoS 2 has potential applications in optoelectronics and spintronics. Also, a band-gap tuning is possible in a MoS 2 bilayer in the presence of a perpendicular electric field E z 14-16 . Additional reported properties of bilayer MoS 2 include magnetoelectric effects and valley-controlled spin-quantum gates 17 , tuning of the valley magnetic moment 18 , and electrical control of the valley-Hall effect 19 . Moreover, a field-effect transistor has been realized experimentally in a few-layer MoS 2 20 . In contrast, bilayer graphene has intrinsically a very weak SOC 21,22 and, when not biased, a zero band gap 23-25 . There exist numerous theoretical and experimental 24,26-29 studies of magnetotransport properties in bilayer graphene. Although its band gap can be controlled by an electric field E z 30-33 , high-quality samples of MoS 2 bilayers with a strong intrinsic SOC and a huge band gap are of particular importance. Contrary to ...

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“…In the limit ξ sτ i → 0, i = 5, .., 8, Eq. (4) gives a LL dispersion similar to that of bilayer graphene 41,42 . The eigenfunctions are…”

Section: A Landau Levelsmentioning

confidence: 87%

“…(8) This LL has exactly the same properties as the n = 0 conventional, non-relativistic LL. For ∆ = λ c = λ v = V = 0, this level has exactly zero energy as the n = 0 LL for bilayer graphene 41,42 . Also, from Eq.…”

Section: A Landau Levelsmentioning

confidence: 92%

Magneto-optical properties of bilayer transition metal dichalcogenides

2018

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In transition metal dichalcogenides the spin-orbit interaction affects differently the conduction and valence band energies as functions of k and the band gap is large. Consequently, when a perpendicular magnetic field B is applied the conduction and valence band Landau levels are also different and this leads to a splitting of the interband optical absorption lines in both the absence and presence of an external electric field Ez. When B and Ez are present the peaks in the imaginary part of the Hall conductivity give two distinct contributions of opposite sign to the interband spectrum. The real part of the right-and left-handed interband conductivity, however, retains its two-peak structure but the peaks are shifted in energy and amplitude with respect to each other in contrast with graphene. The response of the intraband conductivity is significantly modified when the Fermi energy EF and the field B are varied. Its optical spectral weight is found to increase with EF in contrast with the decrease observed in graphene. Further, the position and amplitude of the intraband response depends on the field B. The absorption peaks vary linearly with B for all fields similar to bilayer graphene for low fields but in contrast with the high-field √ B dependence in it.

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Spin-lattice model of magnetoelectric transitions inRbCoBr3

Cited by 16 publications

References 30 publications

Efficient Monte Carlo Algorithm in Quasi-One-Dimensional Ising Spin Systems

Efficient Monte Carlo Algorithm in Quasi-One-Dimensional Ising Spin Systems

Quantum magnetotransport in bilayer MoS2 : Influence of perpendicular electric field

Magneto-optical properties of bilayer transition metal dichalcogenides

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