Superconductivity and pseudogap states in λ-(BEDT-TSF)2GaCl4: Microwave conductivity measurements

Suzuki, Takao; Negishi, E.; Uozaki, H.; Matsui, Hiroshi; Toyota, Naoki

doi:10.1007/bf02679571

Cited by 3 publications

(2 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In particular one needs to take care to account for the possible coexistence of metallic and insulating phases; this is expected as the Mott transition is first order in the organic charge transfer salts. 61,62 The existence of a pseudogap has also been suggested in λ-(BEDT-TSF) 2 GaCl 4 63 from microwave conductivity measurements. The reduction of the real part of the conductivity σ 1 from the Drude conductivity σ dc and the steep upturn in the imaginary part of the conductivity σ 2 may be interpreted in terms of preformed pairs leading to a pseudogap in this material.…”

Section: Open Problems and Future Experimentsmentioning

confidence: 86%

Antiferromagnetic spin fluctuations in the metallic phase of quasi-two-dimensional organic superconductors

2007

View full text Add to dashboard Cite

We give a quantitative analysis of the previously published nuclear magnetic resonance ͑NMR͒ experiments in the -͑ET͒ 2 X family of organic charge-transfer salts. The temperature dependence of the nuclear-spin relaxation rate 1 / T 1 , the Knight shift K s , and the Korringa ratio K is compared to the predictions of the phenomenological spin-fluctuation model of Moriya and Millis, Monien, and Pines ͑M-MMP͒, that has been used extensively to quantify antiferromagnetic spin fluctuations in the cuprates. For temperatures above T NMR Ӎ 50 K, the model gives a good quantitative description of the data in the metallic phases of several -͑ET͒ 2 X materials. These materials display antiferromagnetic correlation lengths which increase with decreasing temperature and grow to several lattice constants by T NMR . It is shown that the fact that the dimensionless Korringa ratio is much larger than unity is inconsistent with a broad class of theoretical models ͑such as dynamical mean-field theory͒ which neglects spatial correlations and/or vertex corrections. For materials close to the Mott insulating phase the nuclear-spin relaxation rate, the Knight shift, and the Korringa ratio all decrease significantly with decreasing temperature below T NMR . This cannot be described by the M-MMP model and the most natural explanation is that a pseudogap, similar to that observed in the underdoped cuprate superconductors, opens up in the density of states below T NMR . Such a pseudogap has recently been predicted to occur in the dimerized organic charge-transfer salts materials by the resonating valence bond ͑RVB͒ theory. We propose specific experiments on organic superconductors to elucidate these issues. For example, measurements to see if high magnetic fields or high pressures can be used to close the pseudogap would be extremely valuable.

show abstract

Section: Open Problems and Future Experimentsmentioning

confidence: 86%

Antiferromagnetic spin fluctuations in the metallic phase of quasi-two-dimensional organic superconductors

2007

View full text Add to dashboard Cite

show abstract

“…However, other interpretations are also possible, in particular one needs to take care to account for the coexistence of metallic and insulating phases; this is expected as the Mott transition is first order in the organic charge transfer salts (Kagawa et al, 2005;Sasaki et al, 2005). The existence of a pseudogap has also been suggested in λ-(BEDT-TSF) 2 GaCl 4 (Suzuki et al, 2006) from microwave conductivity measurements. The reduction of the real part of the conductivity σ 1 from the Drude conductivity σ dc and the steep upturn in the imaginary part of the conductivity σ 2 have been interpreted in terms of preformed pairs leading to a pseudogap in this material.…”

Section: Other Evidence For a Pseudogap In The Weakly Frustrated Mate...mentioning

confidence: 99%

Quantum frustration in organic Mott insulators: from spin liquids to unconventional superconductors

2011

View full text Add to dashboard Cite

We review the interplay of frustration and strong electronic correlations in quasi-two-dimensional organic charge transfer salts, such as (BEDT-TTF) 2 X and EtnMe 4−n P n[Pd(dmit) 2 ] 2 . These two forces drive a range of exotic phases including spin liquids, valence bond crystals, pseudogapped metals, and unconventional superconductivity. Of particular interest is that in several materials with increasing pressure there is a first-order transition from a spin liquid Mott insulating state to a superconducting state. Experiments on these materials raise a number of profound questions about the quantum behaviour of frustrated systems, particularly the intimate connection between spin liquids and superconductivity. Insights into these questions have come from a wide range of theoretical techniques including first principles electronic structure, quantum many-body theory and quantum field theory. In this review we introduce some of the basic ideas of the field by discussing a simple frustrated Heisenberg model with four spins. We then describe the key experimental results, emphasizing that for two materials, κ-(BEDT-TTF) 2 Cu 2 -(CN) 3 and EtMe 3 Sb[Pd(dmit) 2 ] 2 , there is strong evidence for a spin liquid ground state, and for another, EtMe 3 P[Pd(dmit) 2 ] 2 , there is evidence of a valence bond crystal ground state. We review theoretical attempts to explain these phenomena, arguing that they can be captured by a Hubbard model on the anisotropic triangular lattice at half filling, and that Resonating Valence Bond (RVB) wavefunctions capture most of the essential physics. We review evidence that this Hubbard model can have a spin liquid ground state for a range of parameters that are realistic for the relevant materials. In particular, spatial anisotropy and ring exchange are key to destabilising magnetic order. We conclude by summarising the progress made thus far and identifying some of the key questions still to be answered. (S,S13,S24)= J J' J J J 1 2 3 4

show abstract

Persistence of fermionic spin excitations through a genuine Mott transition in κ -type organics

et al. 2022

View full text Add to dashboard Cite

Superconductivity and pseudogap states in λ-(BEDT-TSF)2GaCl4: Microwave conductivity measurements

Cited by 3 publications

References 10 publications

Antiferromagnetic spin fluctuations in the metallic phase of quasi-two-dimensional organic superconductors

Antiferromagnetic spin fluctuations in the metallic phase of quasi-two-dimensional organic superconductors

Quantum frustration in organic Mott insulators: from spin liquids to unconventional superconductors

Persistence of fermionic spin excitations through a genuine Mott transition in κ -type organics

Contact Info

Product

Resources

About