Cooperative phenomena in (TMTSF)2ClO4 : an NMR evidence

Bourbonnais, C.; Creuzet, F.; Jérôme, D.; Bechgaard, K.; Moradpour, Alec

doi:10.1051/jphyslet:019840045015075500

Cited by 114 publications

(107 citation statements)

References 33 publications

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“…2 displays the effective K ρ as a function of temperature: a clear crossover from a LL (with K ρ ≃ 0.7) to a FL (K ρ = 1) is seen as temperature is lowered below T * /W ≃ 1/44. According to [5,8], the crossover scale is given by T * = t ⊥ π C(t ⊥ /t) θ/(1−θ) , with θ = (K ρ + 1/K ρ )/4 − 1/2 (≃ 0.03 here). The interactions reduce its value compared to the naive one t ⊥ /π.…”

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confidence: 99%

Deconfinement Transition and Luttinger to Fermi Liquid Crossover in Quasi-One-Dimensional Systems

et al. 2001

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We investigate a system of one dimensional Hubbard chains of interacting fermions coupled by inter-chain hopping. Using a generalization of the Dynamical Mean Field Theory we study the deconfinement transition from a Mott insulator to a metal and the crossover between Luttinger and Fermi liquid phases. One-particle properties, local spin response and inter-chain optical conductivity are calculated. Possible applications to organic conductors are discussed.PACS numbers: 71.10. Pm,71.10.Hf,71.27+a,71.30+h The nature of the metallic phase of interacting electron systems depends strongly on dimensionality. In three dimensions, Fermi liquid (FL) theory applies, whereas in one dimension the quasi-particle concept breaks down, leading to a different kind of low-energy fixed point known as a Luttinger liquid (LL). For commensurate electron fillings, strong enough repulsive interactions destroy the metallic state altogether by opening a Mott gap. This phenomenon exists in all dimensions but the onedimensional case is particularly favorable [1]. In quasi one-dimensional (Q1D) systems, interchain hopping can induce a (deconfinement) transition from the Mott insulating (MI) state to a metallic state and crossovers between different metallic behaviors (Fig. 1). Besides their intrinsic theoretical interest, understanding these phenomena is directly relevant for a number of compounds such as the organic (super)-conductors (Bechgaard salts), which are three dimensional stacks of quarter-filled chains [2]. Indeed, in these compounds some of the low temperature properties are well described by Fermi liquid theory, whereas optical [3] and transport properties [4] have shown that the high temperature phase is either a Luttinger liquid or a Mott insulator.Describing these Q1D systems is not an easy task. The transverse hopping t ⊥ is a relevant perturbation on the LL [5,6,7]. Hence, perturbative renormalization group calculations yield an estimate of the crossover scale [5,8] but fail below that scale. In the MI state, electrons are confined on the chains by the Mott gap. A finite critical value of t ⊥ is needed to induce an insulator to metal transition. Such a transition has been advocated [9,10]to be at the root of the change from insulating to metallic behavior observed in Bechgaard salts when increasing pressure or when going from the TMTTF to the TMTSF family. Thus the effects of the inter-chain hopping that are the most important physically cannot be handled reliably by perturbative methods. Although some non- perturbative studies of deconfinement have been made for a finite number of chains [11] the case of an infinite system is still open. Some of the key questions yet to be answered are: (i) What is the crossover scale from the LL to MI, or from the LL to FL (Fig.1), and is there only one crossover scale for the different physical properties (transport, spin response, single-particle properties etc...) ? (ii) What is the nature of the low-temperature FL state, and in particular is the shape of the Fermi surface (FS) aff...

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confidence: 99%

Deconfinement Transition and Luttinger to Fermi Liquid Crossover in Quasi-One-Dimensional Systems

et al. 2001

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“…Evidence for such behavior has been found, e.g. in TTF-TCNQ [10] for S(k), and (T MT SF ) 2 ClO 4 [11] for T −1…”

Section: Predictions For Experimentsmentioning

confidence: 84%

A brief introduction to Luttinger liquids

Voit

2000

AIP Conference Proceedings

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Abstract. I give a brief introduction to Luttinger liquids. Luttinger liquids are paramagnetic one-dimensional metals without Landau quasi-particle excitations. The elementary excitations are collective charge and spin modes, leading to charge-spin separation. Correlation functions exhibit power-law behavior. All physical properties can be calculated, e.g. by bosonization, and depend on three parameters only: the renormalized coupling constant K ρ , and the charge and spin velocities. I also discuss the stability of Luttinger liquids with respect to temperature, interchain coupling, lattice effects and phonons, and list important open problems. WHAT IS A LUTTINGER LIQUID ANYWAY?Ordinary, three-dimensional metals are described by Fermi liquid theory. Fermi liquid theory is about the importance of electron-electron interactions in metals. It states that there is a 1:1-correspondence between the low-energy excitations of a free Fermi gas, and those of an interacting electron liquid which are termed "quasiparticles" [1]. Roughly speaking, the combination of the Pauli principle with low excitation energy (e.g. T ≪ E F ) and the large phase space available in 3D, produces a very dilute gas of excitations where interactions are sufficiently harmless so as to preserve the correspondence to the free-electron excitations. Three key elements are: (i) The elementary excitations of the Fermi liquid are quasi-particles. They lead to a pole structure (with residue Z -the overlap of a Fermi surface electron with free electrons) in the electronic Green's function which can be -and has been -observed by photoemission spectroscopy [2]. (ii) Transport is described by the Boltzmann equation which, in favorable cases, can be quantitatively linked to the photoemission response [2]. (iii) The low-energy physics is parameterized by a set of Landau parameters F ℓ s,a which contain the residual interaction effects in the angular momentum charge and spin channels. The correlations in the electron system are weak, although the interactions may be very strong.Fermi liquid theory breaks down for one-dimensional (1D) metals. Technically, this happens because some vertices Fermi liquid theory assumes finite (those involving a 2k F momentum transfer) actually diverge because of the Peierls effect. An equivalent intuitive argument is that in 1D, perturbation theory never can work even for arbitrarily small but finite interactions: when degenerate perturbation

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“…The NMR spin-lattice relaxation rate T −1 1 was among the first properties to show the existence in the Bechgaard salts of spin correlations whose amplitude did not agree with the Fermi liquid prediction [12,13]. In this matter, the temperature dependent T −1 1 data of Figure 2 obtained for (TMTSF) 2 PF 6 are particularly revealing of the importance of antiferromagnetic spin correlations in the normal state near P c .…”

Section: A the Nesting Mechanism: Success And Limitationsmentioning

confidence: 95%

“…On the theoretical side, it is worthy of note that it was at first proposed that these non Fermi liquid effects are attributable to a sizeable reduction − or renormalization − of the one-dimensional temperature scale t * ⊥ as a self-consistent effect of correlations themselves [13]. According to this scheme, a reduction of t * ⊥ would widen the temperature domain in which low-dimensional spin correlations lead to a power law increase of enhancement for the relaxation rate (T 1 T ) −1 ∼ T −γ .…”

Section: A the Nesting Mechanism: Success And Limitationsmentioning

confidence: 99%