Reentrant Mott transition from a Fermi liquid to a spin-gapped insulator in an organic spin-1/2 triangular-lattice antiferromagnet

Shimizu, Yasuhiro; Akimoto, Hikota; Tsujii, H.; Tajima, Akiko; Kato, Reìzo

doi:10.1088/0953-8984/19/14/145240

Cited by 21 publications

(31 citation statements)

References 18 publications

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“…Recently, a number of experiments have identified a handful of materials as candidate spin liquids [4][5][6][7][8][9][10][11][12][13][14]. Both the organic charge transfer salts κ-(BEDT-TTF) 2 Cu 2 (CN) 3 (Refs.…”

Section: Introductionmentioning

confidence: 99%

“…[8][9][10]), where Et = C 2 H 5 and Me = CH 3 are spin-liquid candidates. However, other members of the organic charge transfer salt families κ-(BEDT-TTF) 2 X and Y [Pd(dmit) 2 ] 2 display long-range magnetic order, for example, X = Cu[N(CN) 2 ]Cl or Cu[N(CN) 2 ]Br (for deuterated BEDT-TTF) and Y = Me 4 P, Me 4 As, EtMe 3 As, Et 2 Me 2 P, Et 2 Me 2 As, and Me 4 Sb [3,8,11]. Additionally, the inorganic materials Cs 2 CuCl 4 [12], Ba 3 CoSb 2 O 9 [13], and Ba 3 CuSb 2 O 9 [14] have also been suggested to be spin-liquid candidates.…”

Section: Introductionmentioning

confidence: 99%

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Spin-liquid phase due to competing classical orders in the semiclassical theory of the Heisenberg model with ring exchange on an anisotropic triangular lattice

2014

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We investigate the effect of ring exchange on the ground-state properties and magnetic excitations of the S = 1/2 Heisenberg model on the anisotropic triangular lattice with ring exchange at T = 0 using linear spin-wave theory. Classically, we find stable Néel, spiral and collinear magnetically ordered phases. Upon including quantum fluctuations to the model, linear spin-wave theory shows that ring exchange induces a large quantum disordered region in the phase diagram, completely wiping out the classically stable collinear phase. Analysis of the spin-wave spectra for each of these three models demonstrates that the large spin-liquid phase observed in the full model is a direct manifestation of competing classical orders. To understand the origin of these competing phases, we introduce models where either the four spin contributions from ring exchange, or the renormalization of the Heisenberg terms due to ring exchange are neglected. We find that these two terms favor rather different physics.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Spin-liquid phase due to competing classical orders in the semiclassical theory of the Heisenberg model with ring exchange on an anisotropic triangular lattice

2014

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“…We choose to study spin systems on the triangular lattice because the spin-1/2 organic materials with a triangular lattice are the best experimental candidates for a spin liquid [17][18][19][20][21][22][23][24][25][26], and some of the organic materials in the same family indeed have a columnar VBS order [27]. Our analysis predicts that on an isotropic triangular lattice, the Z 2 liquid to the 12-fold degenerate columnar/plaquette VBS order can be either first order or there could be two transitions with an intermediate phase (Fig.…”

Section: Introductionmentioning

confidence: 99%

Quantum phase transition between theZ2spin liquid and valence bond crystals on a triangular lattice

Slagle

2014

Phys. Rev. B

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We study the quantum phase transition between the Z2 spin liquid and valence bond solid (VBS) orders on a triangular lattice. With a fully isotropic triangular lattice, the transition from a columnar or resonating-plaquette VBS order can be either first order or there could be two transitions with an intermediate phase. If the transition splits into two, then the Z2 spin liquid will first experience a first order q = 3 Potts transition to a new nematic Z2 spin liquid that breaks the 2π/3 lattice rotation symmetry (but retain translation symmetry unlike the VBS states). The second transition will then take this new nematic Z2 spin liquid to a columnar or resonating-plaquette VBS state through a second order 3d XY * transition. On a distorted triangular lattice, the degeneracy between some of the different columnar VBS orders is lifted, and the phase transition can reduce to a single 3d XY * transition.

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“…We parametrize these results in terms of tight binding models and report the parameters found for a number of PdðdmitÞ 2 salts with AFM or charge ordered (CO) ground states. The simplest model that has been proposed for the insulating phases of the PdðdmitÞ 2 salts is the Heisenberg model on the anisotropic triangular lattice [1,2,5]. In this model, each site represents a PdðdmitÞ 2 dimer, J is the exchange coupling around the sides of square, and J 0 is the exchange interaction along one diagonal.…”

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confidence: 99%

Geometrical Frustration in the Spin Liquidβ′−Me3EtSb[Pd(dmit)2
Scriven
¹
,
Powell
²

2012
Phys. Rev. Lett.

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We show that the electronic structures of the title compounds predicted by density functional theory are well described by tight binding models. We determine the frustration ratio, J 0 =J, of the Heisenberg model on the anisotropic triangular lattice, which describes the spin degrees of freedom in the Mott insulating phase for a range of PdðdmitÞ 2 salts. All of the antiferromagnetic materials studied have J 0 =J & 0:5 or J 0 =J * 0:9, and all salts with 0:5 & J 0 =J & 0:9 are known, experimentally, to be charge ordered valencebond solids or spin liquids. DOI: 10.1103/PhysRevLett.109.097206 PACS numbers: 75.10.Kt, 71.15.Mb, 74.70.Kn, 75.10.Jm The interplay of geometrical frustration and electronic correlations produces a wide range of exotic phenomena [1,2] in the organic charge transfer salts Me 4Àn Et n Pn½PdðdmitÞ 2 2 (henceforth Pn-n) [3]. At ambient pressure and low temperature, these materials are Mott insulators, many of which are driven superconducting by the application of hydrostatic pressure or uniaxial stress. Most salts display antiferromagnetic (AFM) order, but recent experiments [1,2] suggest that Me 3 EtP½PdðdmitÞ 2 2 (P-1) is a valence-bond solid (VBS), and Me 3 EtSb½PdðdmitÞ 2 2 (Sb-1) is a type II spin liquid (SL) [2], with a singlet gap but no triplet gap [4].In this Letter, we report density functional theory (DFT) calculations of the electronic structures of Sb-1 and P-1. We parametrize these results in terms of tight binding models and report the parameters found for a number of PdðdmitÞ 2 salts with AFM or charge ordered (CO) ground states. The simplest model that has been proposed for the insulating phases of the PdðdmitÞ 2 salts is the Heisenberg model on the anisotropic triangular lattice [1,2,5]. In this model, each site represents a PdðdmitÞ 2 dimer, J is the exchange coupling around the sides of square, and J 0 is the exchange interaction along one diagonal. We find that those materials that display long-range AFM order lie in the parameter regimes J 0 =J & 0:5 or J 0 =J * 1 where many-body theories predict long-range magnetic order. Further, all of the materials with CO, SL, or VBS ground states lie in the parameter regime 0:5 & J 0 =J & 0:9 where the low energy physics remains controversial because there are a number of competing states. We argue that this means that other terms in the Hamiltonian may be crucial for determining the ground state.The Heisenberg model on the anisotropic triangular lattice has been studied by a range of theoretical methods including linear spin-wave theory [6] [19]. Collectively, these studies suggest that Néel (, ) order is realized for J 0 =J & 0:5, and incommensurate (q, q) long-range AFM order is realized for J 0 =J $ 1 (in the special case J 0 =J ¼ 1, the 120 state with q ¼ 2=3 is realized). However, the ground state for 0:6 & J 0 =J & 0:9 remains controversial.Many PdðdmitÞ 2 salts undergo a Mott transition under hydrostatic pressure and/or uniaxial strain [1,2]. Therefore, it is possible that the Heisenberg model misses some essential physi...

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Reentrant Mott transition from a Fermi liquid to a spin-gapped insulator in an organic spin-1/2 triangular-lattice antiferromagnet

Cited by 21 publications

References 18 publications

Spin-liquid phase due to competing classical orders in the semiclassical theory of the Heisenberg model with ring exchange on an anisotropic triangular lattice

Spin-liquid phase due to competing classical orders in the semiclassical theory of the Heisenberg model with ring exchange on an anisotropic triangular lattice

Quantum phase transition between theZ2spin liquid and valence bond crystals on a triangular lattice

Geometrical Frustration in the Spin Liquidβ′−Me3EtSb[Pd(dmit)2
Scriven
¹
,
Powell
²

2012
Phys. Rev. Lett.

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Reentrant Mott transition from a Fermi liquid to a spin-gapped insulator in an organic spin-1/2 triangular-lattice antiferromagnet

Cited by 21 publications

References 18 publications

Spin-liquid phase due to competing classical orders in the semiclassical theory of the Heisenberg model with ring exchange on an anisotropic triangular lattice

Spin-liquid phase due to competing classical orders in the semiclassical theory of the Heisenberg model with ring exchange on an anisotropic triangular lattice

Quantum phase transition between theZ2spin liquid and valence bond crystals on a triangular lattice

Geometrical Frustration in the Spin Liquidβ′−Me3EtSb[Pd(dmit)2Scriven1, Powell2 2012Phys. Rev. Lett.

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Geometrical Frustration in the Spin Liquidβ′−Me3EtSb[Pd(dmit)2
Scriven
¹
,
Powell
²

2012
Phys. Rev. Lett.