FIG 8 - uploaded by Hao Zhang
Content may be subject to copyright.
(Color online) SSCF for a system of size N = 2 × 50 × 50 in the armchair direction corresponding to the four different phases: (a) J 2 /J 1 = 0.18 (Néel), (b) J 2 /J 1 = 0.36 (GSL), (c) J 2 /J 1 = 0.38 (staggered-dimer VBC), and (d) J 2 /J 1 = 0.48 (spiral).
Source publication
We study the ground-state phase diagram of the frustrated quantum $J_1-J_2$
Heisenberg antiferromagnet on the honeycomb lattice using a mean field approach
in terms of the Schwinger boson representation of the spin operators. We
present results for the ground-state energy, local magnetization, energy gap
and spin-spin correlations. The system shows...
Similar publications
https://arxiv.org/abs/1804.08630 The spin-1/2 square-lattice Heisenberg model is predicted to have a quantum disordered ground state when magnetic frustration is maximized by competing nearest-neighbor $J_1$ and next-nearest-neighbor $J_2$ interactions ($J_2/J_1 \approx 0.5$). The double perovskites Sr$_2$CuTeO$_6$ and Sr$_2$CuWO$_6$ are isostructu...
We explore the effect of the third nearest-neighbors on the magnetic
properties of the Heisenberg model on an anisotropic triangular lattice. We
obtain the phase diagram of the model using Schwinger-boson mean-field theory.
Competition between N\'eel, spiral and collinear magnetically ordered phases is
found as we vary the on the ratios of the near...
The measurements on temperature dependence of magnetic susceptibility χ(T), specific heat C(T) and electrical resistivity ρ(T) were carried out for the antiferromagnetic (AFM) (Ce1−xLax)2Ir3Ge5 (0.0 ≤ x ≤ 0.66) system. It was found that the Neel temperature, TN , decreases with increasing La content, x, and reaches to zero kelvin near a critical co...
The Kitaev-Heisenberg model on the honeycomb lattice has been studied for the purpose of finding exotic states such as quantum spin liquid and topological orders. On the kagome lattice, in spite of a spin-liquid ground state in the Heisenberg model, the stability of the spin-liquid state has hardly been studied in the presence of the Kitaev interac...
The effects of electron doping and phonon vibrations on the magnetic
properties of monolayer and bilayer FeSe epitaxial films on SrTiO$_3$ have been
studied, respectively, using first-principles calculations with van der Waals
correction. For monolayer FeSe epitaxial film, the combined effect of electron
doping and phonon vibrations readily leads t...
Citations
... A spiral spin-liquid (SSL) is an exotic type of correlated paramagnetic state where the low energy dynamics consist of collective spiral correlations [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. A characteristic feature of a SSL is that the propagation vectors of the degenerate spiral ground states form a continuous surface in reciprocal space [1]. ...
... S13(b-d) reproduce the q I = ( 1 2 , 1 2 , 0) in zero field and q III = 5 6 × ( 1 3 , 1 3 , 0) at H = 5 T. Therefore, we conclude that FM J 5 is the main perturbative term to the J 123 + D z Hamiltonian, leading to a J 123 + D z + J 5 model that is employed in the main text. [4,7], and (c) [8,14] T. Data are normalized by the maximal Cp value, C max p . The strength of the applied field for each curve is indicated on the left. ...
A codimension-two spiral spin-liquid is a correlated paramagnetic state with one-dimensional ground state degeneracy hosted within a three-dimensional lattice. Here, via neutron scattering experiments and numerical simulations, we establish the existence of a codimension-two spiral spin-liquid in the effective honeycomb-lattice compound Cs$_3$Fe$_2$Cl$_9$ and demonstrate the selective visibility of the spiral surface through phase tuning. In the long-range ordered regime, competing spiral and spin density wave orders emerge as a function of applied magnetic field, among which a possible order-by-disorder transition is identified.
... In sharp contrast to the long-range Néel order state in an isotropic nearest-neighbor exchange model on the honeycomb lattice [37][38][39][40][41][42], the strong quantum fluctuations induced by further nearest-neighbor frustrated exchange interaction can destabilize the Néel order even in bipartite honeycomb lattices [43][44][45][46]. The bipartite spin lattice of rare-earth-based honeycomb magnets offers a promising venue to host spiral spin-liquid state with fracton quadrupole excitations [47,48], multiple-q states in the presence of magnetic field [49], lattice nematic phase [50], and Berezinskii-Kosterlitz-Thouless phase [51,52]. In this context, structurally perfect novel rareearth 4 f -based honeycomb magnets wherein the combination of spin-orbit coupling and sizable crystal electric field allows for the realization of an effective spin- 1 2 system with large anisotropy and strong spin correlation. ...
The interplay between spin-orbit coupling, anisotropic magnetic interaction, frustration-induced quantum fluctuations, and spin correlations can lead to novel quantum states with exotic excitations in rare-earth-based quantum magnets. Herein, we present the crystal structure, magnetization, electron spin resonance (ESR), specific heat, and nuclear magnetic resonance (NMR) experiments on the polycrystalline samples of Ba9Yb2Si6O24, in which Yb3+ ions form a perfect honeycomb lattice without detectable antisite disorder. The magnetization data reveal antiferromagnetically coupled spin-orbit entangled Jeff=12 degrees of freedom of Yb3+ ions in the Kramers doublet state. The ESR measurements reveal that the first excited Kramers doublet is 32.3(7) meV above the ground state. The specific heat results suggest the absence of any long-range magnetic order in the measured temperature range. Furthermore, the Si29 NMR results do not indicate any signature of magnetic ordering down to 1.6 K, and the spin-lattice relaxation rate reveals the presence of a field-induced gap that is attributed to the Zeeman splitting of the Kramers doublet state in this quantum material. Our experiments detect neither spin freezing nor long-range magnetic ordering down to 1.6 K. The current results suggest the presence of short-range spin correlations in this spin-orbit entangled Jeff=12 rare-earth magnet on a honeycomb lattice.
... The strong quantum fluctuations of effective-1/2 spins, in combination with anisotropic interactions arising from strong spin-orbit coupling in rare-earth based magnets can lead to a plethora of quantum phases compared to traditional transition metal based magnets [46,49,63,64]. Besides the promising platform to realize of Kitaev spin liquid ground state in rare-earth based honeycomb magnets [65], such bipartite spin-lattice offers a promising venue to host spiral spin-liquid state with fracton quadrupole excitations [66,67], multiple-q states in presence of magnetic field [68], lattice nematic phase [69], and Berezinskii-Kosterlitz-Thouless phase [70,71] . Furthermore, the realization of quantum phase transition [72][73][74] and multiple exotic phases associated with a fully frustrated transverse-field Ising model in a honeycomb lattice are yet to be explored [75,76]. ...
The interplay between spin-orbit coupling, frustration-induced anisotropic magnetic interaction, and spin correlations can lead to novel states with exotic excitations in rare-earth-based quantum magnets. Herein, we present the crystal structure, magnetization, electron spin resonance (ESR), specific heat, and nuclear magnetic resonance (NMR) experiments on the polycrystalline samples of Ba9Yb2Si6O24 in which Yb3+ ions form a perfect honeycomb lattice without detectable anti-site disorder. Magnetization data reveal antiferromagnetically coupled spin-orbit entangled Jeff = 1/2 degrees of freedom of Yb3+ ions in the Kramers doublet state where the Curie-Weiss temperature is - 2.97 K, as obtained from the low-temperature magnetic susceptibility data. The ESR measurements reveal that the first excited Kramers doublet is 32.3(7) meV above the ground state. The specific heat results suggest the presence of an antiferromagnetic phase transition at 2.26 K. The long-range antiferromagnetic order is completely suppressed upon the application of magnetic field and a field-induced disordered state is observed in an applied magnetic field of 2.5 T, which is also confirmed by NMR measurements. Furthermore, the NMR spin-lattice relaxation rate reveals the presence of a field-induced gap that is attributed to the Zeeman splitting of Kramers doublet state in this quantum material. Our experiments suggest the presence of a phase transition and short-range spin correlations appearing well above the antiferromagnetic phase transition temperature and a field-induced disordered state in this spin-orbit entangled Jeff =1/2 rare-earth magnet on a honeycomb lattice.
... We call the rest of the gapped region a GSL state. These findings match with previous studies [56,67]. ...
We theoretically investigate, within Schwinger-boson mean-field theory, the transition from a gapped Z 2 quantum spin liquid, in a J 1-J 2 Heisenberg spin-1 2 system in a honeycomb lattice, to a chiral Z 2 spin-liquid phase under the presence of time-reversal symmetry-breaking scalar chiral interaction (with amplitude J χ). We numerically obtain a phase diagram of this J 1-J 2-J χ system, where different ground states are distinguished based on the gap and the nature of excitation spectrum, topological invariant of the excitations, the nature of spin-spin correlation, and the symmetries of the mean-field parameters. The chiral Z 2 state is characterized by the nontrivial Chern number of the excitation bands and lack of long-range magnetic order, which leads to a large thermal Hall coefficient.
... Introduction.-A spiral spin liquid (SSL) is an exotic correlated paramagnetic state of sub-dimensional degeneracy, meaning that the propagation vectors q of the ground states form a continuous manifold, or spiral surface, in a dimension that is reduced from the original system [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Similar to geometrically frustrated magnets [15,16], a SSL may host topological spin textures [17][18][19] and quantum spin liquid states [3][4][5][20][21][22]. ...
... spiral spin liquid (SSL) is an exotic correlated paramagnetic state of sub-dimensional degeneracy, meaning that the propagation vectors q of the ground states form a continuous manifold, or spiral surface, in a dimension that is reduced from the original system [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Similar to geometrically frustrated magnets [15,16], a SSL may host topological spin textures [17][18][19] and quantum spin liquid states [3][4][5][20][21][22]. What differentiates a SSL from a conventional frustrated magnet is the sub-dimensional degeneracy, which induces highly distinctive dynamics since the spins are confined to fluctuate collectively as nonlocal spirals [23]. ...
Competition among exchange interactions is able to induce novel spin correlations on a bipartite lattice without geometrical frustration. A prototype example is the spiral spin liquid, which is a correlated paramagnetic state characterized by sub-dimensional degenerate propagation vectors. Here, using spectral graph theory, we show that spiral spin liquids on a bipartite lattice can be approximated by a further-neighbor model on the corresponding line-graph lattice that is non-bipartite, thus broadening the space of candidate materials that may support the spiral spin liquid phases. As illustrations, we examine neutron scattering experiments performed on two spinel compounds, ZnCr$_2$Se$_4$ and CuInCr$_4$Se$_8$, to demonstrate the feasibility of this new approach and expose its possible limitations in experimental realizations.
... This work opens several future research directions. The algorithm can be naturally applied to the frustrated Heisenberg antiferromagnets with NNN and even longerrange interactions [46][47][48][49][50][51][52]. Upon certain technical modifications, it can also be employed for the star lattice geometry [8]. ...
We develop a method of variational optimization of the infinite projected entangled pair states on the honeycomb lattice. The method is based on the automatic differentiation of the honeycomb lattice corner transfer matrix renormalization group. We apply the approach to the antiferromagnetic Heisenberg spin-1/2 model on the honeycomb lattice. The developed formalism gives quantitatively accurate results for the main physical observables and has a necessary potential for further extensions.
... The Schwinger boson method has been very popular in the study of frustrated magnets, for one, because it is able to treat both ordered and disordered ground states on an equal footing. It has been successful on a variety of frustrated models to analytically study their ground states [81] and establish full phase diagrams [38,82,83]. It is also quite versatile as it can be extended to various other models such as the XXZ model [84] or the Heisenberg model with additional Dzyaloshinskii-Moriya coupling [85]. ...
Frustrated quantum magnets have received a lot of attention in the past decades for they are expected to host exotic magnetic states such as quantum spin liquids exhibiting fractionalized excitations and topological properties. One way to study these spin liquid phases is to perform a parton construction of the quantum Heisenberg Hamiltonian. This mean-field method has the valuable advantage of treating magnetically ordered states and spin-liquid states on an equal footing. In this thesis, we have employed such a method based on the Schwinger boson mean-field theory (SBMFT) to study two magnetically frustrated systems. After a brief introduction of the core concepts behind frustrated magnetic systems in chapter 1 we will introduce the Schwinger boson theory and the associated numerical tools in chapter 2. In chapter 3, we will present the full phase diagram of the J1-J2 Heisenberg model on the square-kagome lattice with a particurlarly interesting ground state in the form of a topological nematic spin liquid. We will then make connections with a recently synthesized compound exhibiting perfect square-kagome geometry. In the final chapter of this manuscript, we will turn to the J1-J2-J3 Heisenberg model on the kagome lattice in the case where J2=J3=J. Once again, a full phase diagram is obtained thanks to our SBMFT self-consistent procedure. It is composed of three distinct ground states: a chiral spin liquid for J<1/3, a chiral long-range order for J>1/2 and a symmetric spin liquid in between. Finally, we will make connections with previous quantum and classical works, especially by discussing the presence of half-moon patterns in the static structure factor of an excited state of the model for J>1/2. In conclusion, we have revealed both rich and complex phase diagrams presenting various exotic spin-liquid states on the two frustrated systems studied in this manuscript.
... Similar to geometrical frustration [1,2], competition amongst interactions at different length scales is able to induce novel electronic or magnetic states regardless of the lattice geometry. A representative example is the spiral spin-liquid (SSL), which is a type of classical spin liquid realized on a bipartite lattice [3][4][5][6][7][8][9][10][11][12][13][14][15][16]. In such a state, spins fluctuate collectively as spirals, and their propagation vectors, q, form a continuous ring or surface in reciprocal space. ...
... This enables delicate degeneracy relieving effects like order-by-disorder transitions [3,7]. Since degeneracy enhances quantum fluctuations [2,17], the SSL has been proposed as a novel route to realize quantum spin liquids in systems dominated by ferromagnetic interactions [5][6][7][8]. On the other hand, when perturbations, e.g. the further-neighbor interactions or anisotropic interactions, induce a magnetic long-range order, degeneracy in the SSL may be partially * This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. ...
Spiral spin-liquids are correlated paramagnetic states with degenerate propagation vectors forming a continuous ring or surface in reciprocal space. On the honeycomb lattice, spiral spin-liquids present a novel route to realize quantum spin liquids and topological spin textures, although their experimental realization remains elusive. Here, using neutron scattering, we show that a spiral spin-liquid is realized in the van der Waals honeycomb magnet FeCl$_3$. A continuous ring of scattering in reciprocal space is directly observed, and the intensity distribution is accurately described by a Heisenberg model with competing exchange interactions. Our work demonstrates that spiral spin-liquids can be realized in two-dimensional systems and represents a crucial step in the quest for quantum spin liquids and topological spin textures on the honeycomb lattice.
... For this reason, it is expected that the correlations are strong in this system. The small coordination number together with frustrated interactions has been shown to have interesting effects in the Heisenberg model on this lattice, where the phase diagram shows a magnetically disordered region and a spin-liquid phase [30,31]. From the experimental point of view, several materials regarded as realizations of spin systems on honeycomb lattices have been synthesized [32][33][34][35][36]. Therefore, the complexity and interest of this model make it a candidate for testing the ability of unsupervised techniques to detect transitions in two-dimensional frustrated systems. ...
The transfer learning of a neural network is one of its most outstanding aspects and has given supervised learning with neural networks a prominent place in data science. Here we explore this feature in the context of strongly interacting many-body systems. Through case studies, we test the potential of this deep learning technique to detect phases and their transitions in frustrated spin systems, using fully-connected and convolutional neural networks. In addition, we explore a recently-introduced technique, which is at the middle point of supervised and unsupervised learning. It consists in evaluating the performance of a neural network that has been deliberately “confused” during its training. To properly demonstrate the capability of the “confusion” and transfer learning techniques, we apply them to a paradigmatic model of frustrated magnetism in two dimensions, to determine its phase diagram and compare it with high-performance Monte Carlo simulations.
... Distant correlations capture interesting physical properties (for example, phase transitions [1][2][3][4][5][6][7][8][9] in exotic phases) of the quantum spin system, which is a typical strongly correlated quantum many body system. But as the dimension of the Hilbert space grows exponentially with the system size, it is difficult to solve a large system exactly. ...
We propose an optimized cluster density matrix embedding theory (CDMET). It reduces the computational cost of CDMET with simpler bath states. And the result is as accurate as the original one. As a demonstration, we study the distant correlations of the Heisenberg J 1 – J 2 model on the square lattice. We find that the intermediate phase (0.43 ≲ J 2 ≲ 0.62) is divided into two parts. One part is a near-critical region (0.43 ≲ J 2 ≲ 0.50). The other part is the plaquette valence bond solid (PVB) state (0.51 ≲ J 2 ≲ 0.62). The spin correlations decay exponentially as a function of distance in the PVB.
