Crystal structure and physical properties of α-(BEDT-TTF)2MM' (SCN)4 [M=Rb,Cs,M'=Co,Zn]

Mori, H.; Tanaka, Shōji; Mori, Toshiyuki; Fuse, Akinori

doi:10.1016/s0379-6779(97)80905-8

Cited by 9 publications

(8 citation statements)

References 3 publications

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“…An absence of a change of magnetic susceptibility at T=30 K is unexpected: The character of χ M (T ) is expected to change from Pauli to a behavior of an insulator with unpaired spins or a spin singlet state. The absence of a change in χ M (T ) is in contrast to the behavior of magnetic susceptibility observed on charge order metalinsulator transitions in other 2D BEDT-TTF-based materials, which showed a formation of a spin singlet in the charge ordered insulating state [26,31]. The paramagnetic behavior below the transition temperatures is confirmed by the cantilever magnetic torque measurements.…”

Section: Introductionmentioning

confidence: 54%

“…Decreasing susceptibility in a small temperature range between 24 K and 15 K can be fit by a magnetic susceptibility of a gapped system e − ∆ k B T , which yields a gap ∆ =36 K=1.5 Tc. A transition to a spin-singlet or anitiferromagnetically ordered state can be expected in this charge ordered system, based both on theory [25] and on experimentally observed behavior of other charge-ordered materials [26,33].…”

Section: Introductionmentioning

confidence: 92%

“…1D antiferromagnetic (AF) stripes can result in a 1D spin liquid, presenting another possible way to reach a spin liquid state for κ-HgCl [23,24]. Alternatively, a strong coupling of spin degrees of freedom to the lattice can result in a formation of a spin singlet state [25], as observed, for example, in θ-(BEDT-TTF) 2 RbZn(SCN) 4 [26].…”

Section: Introductionmentioning

confidence: 99%

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Charge and spin interplay in a molecular-dimer-based organic Mott insulator

Drichko,

Sugiura,

Yamashita

et al. 2021

Preprint

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Triangular lattice quasi-two-dimensional Mott insulators based on BEDT-TTF molecule and its analogies present the largest group of spin liquid candidates on triangular lattice. It was shown theoretically that spin liquid state in these materials can arize from a coupling to the fluctuating charge degree of freedom. In this work we discuss magnetic properties of one of such materials, κ-(BEDT-TTF)2Hg(SCN)2Cl, which is known to be at the border of the phase transition from Mott insulator into a charge ordered state, and demonstrates charge order properties in the temperature range from 30 to 15 K. Our magnetic susceptibility and cantilever magnetisation measurements demonstrate an absence of spin order in this material down to 120 mK. We present arguments demonstrating that the charge order melting at low temperatures prevents ordering of spins.

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Section: Introductionmentioning

confidence: 54%

Section: Introductionmentioning

confidence: 92%

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Charge and spin interplay in a molecular-dimer-based organic Mott insulator

Drichko,

Sugiura,

Yamashita

et al. 2021

Preprint

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“…Besides X=I 3 , a variety of θ salts with X=MM (SCN) 4 are known, which in general undergo MI transitions between 20 and 250 K (see Fig. 31) [406][407][408]. The θ CTS have been grouped into a phase diagram shown in Fig.…”

Section: θ Ctsmentioning

confidence: 99%

From charge- and spin-ordering to superconductivity in the organic charge-transfer solids

Clay,

Mazumdar

2018

Preprint

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We review recent progress in understanding the different spatial broken symmetries that occur in the normal states of the family of charge-transfer solids (CTS) that exhibit superconductivity (SC), and discuss how this knowledge gives insight to the mechanism of the unconventional SC in these systems. A great variety of spatial broken symmetries occur in the semiconducting states proximate to SC in the CTS, including charge ordering, antiferromagnetism and spin-density wave, spin-Peierls state and the quantum spin liquid. We show that a unified theory of the diverse broken symmetry states necessarily requires explicit incorporation of strong electron-electron interactions and lattice discreteness, and most importantly, the correct bandfilling of one-quarter, as opposed to the effective half-filled band picture that is often employed. Uniquely in the quarter-filled band, there is a very strong tendency to form nearest neighbor spin-singlets, in both one-and two-dimension. The spin-singlet in the quarter-filled band is necessarily charge-disproportionated, with charge-rich pairs of nearest neighbor sites separated by charge-poor pairs of sites in the insulating state. Thus the tendency to spin-singlets, a quantum effect, drives a commensurate charge-order in the correlated quarter-filled band. This charge-ordered spin-singlet, which we label as a paired-electron crystal (PEC), is different from and competes with both the antiferromagnetic (AFM) state and the Wigner crystal (WC) of single electrons. Further, unlike these classical broken symmetries, the PEC is characterized by a spin gap. The tendency to the PEC in two dimension is enhanced by lattice frustration. The concept of the PEC mirrors parallel development of the idea of a density wave of Cooper pairs in the superconducting high T c cuprates, where also the existence of a charge-ordered state in between the antiferromagnetic and the superconducting phase has now been confirmed. Following this characterization of the spatial broken symmetries, we critically reexamine spin-fluctuation and resonating valence bond theories of frustration-driven SC within half-filled band Hubbard and Hubbard-Heisenberg Hamiltonians for the superconducting CTS. We present numerical evidence for the absence of SC within the half-filled band correlated-electron Hamiltonians for any degree of frustration. We then develop a valence-bond theory of SC within which the superconducting state is reached by the destabilization of the PEC by additional pressure-induced lattice frustration that makes the spin-singlets mobile. We present limited but accurate numerical evidence for the existence of such a charge order-SC duality. Our proposed mechanism for SC is the same for CTS in which the proximate semiconducting state is antiferromagnetic instead of charge-ordered, with the only difference that SC in the former is generated via a fluctuating spin-singlet state as opposed to static PEC. In Appendix B we point out that several classes of unconventional superconductors share the same band-fil...

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“…5) Recently another 2D organic compound θ-(ET) 2 RbZn(SCN) 4 has been synthesized which shows a SG behavior. 7) The existence of a SG has been suggested from magnetic susceptibility 8,9) and NMR 10) measurements. The θ-type ET compounds in general have a donor structure with two ET molecules in a unit cell as shown in Fig.…”

mentioning

confidence: 99%

Frustrated Spin System inθ-(BEDT-TTF)₂RbZn(SCN)₄

Seo

Fukuyama

1998

J. Phys. Soc. Jpn.

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The origin of the spin gap behavior in the low-temperature dimerized phase of θ-(BEDT-TTF)2RbZn(SCN)4 has been theoretically studied based on the Hartree-Fock approximation for the on-site Coulomb interaction at absolute zero. Calculations show that, in the parameter region considered to be relevant to this compound, antiferromagnetic ordering is stabilized between dimers consisting of pairs of molecules coupled with the largest transfer integral. Based on this result an effective localized spin 1/2 model is constructed which indicates the existence of the frustration among spins. This frustration may result in the formation of spin gap.

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Crystal structure and physical properties of α-(BEDT-TTF)2MM' (SCN)4 [M=Rb,Cs,M'=Co,Zn]

Cited by 9 publications

References 3 publications

Charge and spin interplay in a molecular-dimer-based organic Mott insulator

Charge and spin interplay in a molecular-dimer-based organic Mott insulator

From charge- and spin-ordering to superconductivity in the organic charge-transfer solids

Frustrated Spin System inθ-(BEDT-TTF)₂RbZn(SCN)₄

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Crystal structure and physical properties of α-(BEDT-TTF)2MM' (SCN)4 [M=Rb,Cs,M'=Co,Zn]

Cited by 9 publications

References 3 publications

Charge and spin interplay in a molecular-dimer-based organic Mott insulator

Charge and spin interplay in a molecular-dimer-based organic Mott insulator

From charge- and spin-ordering to superconductivity in the organic charge-transfer solids

Frustrated Spin System inθ-(BEDT-TTF)2RbZn(SCN)4

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Frustrated Spin System inθ-(BEDT-TTF)₂RbZn(SCN)₄