Mott metal-insulator transition induced by utilizing a glasslike structural ordering in low-dimensional molecular conductors

Hartmann, Benedikt; Müller, Jens; Sasaki, T.

doi:10.1103/physrevb.90.195150

Cited by 28 publications

(44 citation statements)

References 33 publications

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“…These crystals, with typical dimensions a × b × c ≈ 0.7 × 1 × 0.5 mm 3 were grown following the standard electrochemical procedure ( 52 ). Before the measurements, the crystals were cooled through the glass transition T g ≈ 67 K by using a slow cooling rate of −3 K/hour to reduce disorder in the ethylene end groups of the BEDT-TTF molecules ( 53 ). …”

Section: Methodsmentioning

confidence: 99%

Breakdown of Hooke’s law of elasticity at the Mott critical endpoint in an organic conductor

et al. 2016

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Section: Methodsmentioning

confidence: 99%

Breakdown of Hooke’s law of elasticity at the Mott critical endpoint in an organic conductor

et al. 2016

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“…In a recent work, we could demonstrate that, when thermally coupled to a lowtemperature heat bath, a pulsed heating current through the sample causes a very fast relaxation with cooling rates at T g of the order of several 1000 K min −1 [12]. The sudden freezing of the structural degrees of freedom causes a decrease of the electronic bandwidth W with increasing cooling rate, and hence a Mott metal-insulator transition for metallic systems crossing the critical ratio W U c ( ) of bandwidth to on-site Coulomb repulsion U; see [12,41]. Due to the glassy character of the transition, the effect is persistent below T g and can be reversibly repeated by melting the frozen configuration upon warming above T g .…”

Section: Introductionmentioning

confidence: 99%

“…Due to the glassy character of the transition, the effect is persistent below T g and can be reversibly repeated by melting the frozen configuration upon warming above T g . Both by exploiting the characteristics of slowly changing relaxation times close to this temperature and by controlling the heating power, the materials can be fine-tuned across the Mott transition [12,41].…”

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Origin of the glass-like dynamics in molecular metalsκ-(BEDT-TTF)₂X: implications from fluctuation spectroscopy andab initiocalculations

et al. 2015

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We have studied the low-frequency dynamics of the charge carriers in different organic chargetransfer salts κ-(BEDT-TTF) 2 X with polymeric anions X by using resistance noise spectroscopy. Our aim is to investigate the structural, glass-like transition caused by the conformational degrees of freedom of the BEDT-TTF molecules' terminal ethylene groups. Although of fundamental importance for studies of the electronic ground-state properties, the phenomenology of the glassy dynamics has been minimally investigated and its origin is not understood. Our systematic studies of fluctuation spectroscopy of various different compounds reveal a universal, pronounced maximum in the resistance noise power spectral density related to the glass transition. The energy scale of this process can be identified with the activation energy of the glass-like ethylene endgroup structural dynamics as determined from thermodynamic and NMR measurements. For the first time for this class of 'plastic crystals', we report a typical glassy property of the relaxation time, namely a Vogel-Fulcher-Tammann law, and are able to determine the degree of fragility of the glassy system. Supporting ab initio calculations provide an explanation for the origin and phenomenology of the glassy dynamics in different systems in terms of a simple two-level model, where the relevant energy scales are determined by the coupling of the ethylene endgroups to the anions.

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“…1, has been widely used in κ-Br compounds with different type and degree of deuteration of the ET molecules [17,18,27,28]. The effect originates in an anisotropic change of the in-plane lattice parameters at T g , which changes the relevant transfer integrals such that more rapid cooling leads to slightly smaller bandwidth (and W/U ratio) [17,25]. In Fig.…”

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Critical Slowing Down of the Charge Carrier Dynamics at the Mott Metal-Insulator Transition

et al. 2015

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We report on the dramatic slowing down of the charge carrier dynamics in a quasi-two-dimensional organic conductor, which can be reversibly tuned through the Mott metal-insulator transition (MIT). At the finite-temperature critical endpoint we observe a divergent increase of the resistance fluctuations accompanied by a drastic shift of spectral weight to low frequencies, demonstrating the critical slowing down of the order parameter (doublon density) fluctuations. The slow dynamics is accompanied by non-Gaussian fluctuations, indicative of correlated charge carrier dynamics. A possible explanation is a glassy freezing of the electronic system as a precursor of the Mott MIT.The Mott metal-insulator transition (MIT), where a charge gap opens due to electron-electron interactions is a key phenomenon in modern condensed-matter physics [1], for which the understanding of various fundamental aspects remains challenging, both theoretically and experimentally [2]. Among them are the nature of the anomalous metallic state and (nano-scale) phase separation in the vicinity of the Mott transition, the understanding of the combined effects of electron-electron interactions and disorder, and the question of universality and critical behavior. In recent years, organic charge-transfer salts have proven an outstanding class of materials with model character for studying these aspects of the Mott MIT [2-5]. These materials κ-(BEDT-TTF) 2 X, composed of the organic donor molecule BEDT-TTF (bis-ethylenedithio-tetrathiafulvalene representing C 6 S 8 [C 2 H 4 ] 2 , abbreviated as ET) and a polymeric anion X, are layered systems with a quasi-twodimensional electronic structure and belong to the very few examples, where the Mott MIT is purely driven by controlling the bandwidth without symmetry breaking [6]. The bandwidth W can be covontrolled either continuously by applying hydrostatic pressure or in discrete steps at ambient pressure by varying the anion X, which mimics changes in the ratio W/U , where U is the effective on-site Coulomb repulsion [7]. Likewise, replacing the eight H-atoms of the ET molecules' C 2 H 4 ethylene endgroups (EEG) in metallic κ-(ET) 2 Cu[N(CN) 2 ]Br (κ-H 8 -Br) by D-atoms (κ-D 8 -Br) results in a chemicallyinduced shift from the metallic towards the Mott insulating state [8]. In the T -p or T -X phase diagram the MIT is represented by an S-shaped, first-order transition line which terminates in a second-order critical point (p cr. /T cr. ), see Fig. 1. Recently, the critical behavior of the charge, spin and lattice degrees of freedom at (p cr. /T cr. ) has been subject of intense research efforts [6,[9][10][11][12][13][14][15]. Despite numerous experimental and theoretical approaches, however, no consensus has been reached on the nature of the Mott criticality in κ-(ET) 2 X and the underlying universality class. Furthermore, an investigation of the critical fluctuations and the dynamic properties of the charge carriers at the critical point, in particular at low frequencies, is still lacking. From general ...

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Mott metal-insulator transition induced by utilizing a glasslike structural ordering in low-dimensional molecular conductors

Cited by 28 publications

References 33 publications

Breakdown of Hooke’s law of elasticity at the Mott critical endpoint in an organic conductor

Breakdown of Hooke’s law of elasticity at the Mott critical endpoint in an organic conductor

Origin of the glass-like dynamics in molecular metalsκ-(BEDT-TTF)₂X: implications from fluctuation spectroscopy andab initiocalculations

Critical Slowing Down of the Charge Carrier Dynamics at the Mott Metal-Insulator Transition

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Mott metal-insulator transition induced by utilizing a glasslike structural ordering in low-dimensional molecular conductors

Cited by 28 publications

References 33 publications

Breakdown of Hooke’s law of elasticity at the Mott critical endpoint in an organic conductor

Breakdown of Hooke’s law of elasticity at the Mott critical endpoint in an organic conductor

Origin of the glass-like dynamics in molecular metalsκ-(BEDT-TTF)2X: implications from fluctuation spectroscopy andab initiocalculations

Critical Slowing Down of the Charge Carrier Dynamics at the Mott Metal-Insulator Transition

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Origin of the glass-like dynamics in molecular metalsκ-(BEDT-TTF)₂X: implications from fluctuation spectroscopy andab initiocalculations