Optical Conductivity in a Two-Dimensional Extended Hubbard Model for an Organic Dirac Electron System α-(BEDT-TTF)2I3

Ohki, Daigo; Matsuno, Genki; Omori, Yukiko; Kobayashi, Akito

doi:10.3390/cryst8030137

Cited by 9 publications

(16 citation statements)

References 41 publications

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“…Upon further increasing V a , the merging transition takes place at V c2 a = 0.211 (at T = 0.0005) where the system changes from the (charge-ordered) massive Dirac state (V c2 a > V a > V c a ) to the charge-ordered state with no Dirac cones (V a > V c2 a ) (As we mentioned previously, the valley Chern number changes from a finite value to zero across this transition [15], but in both phases metallic bound states exist along the domain wall). The latter critical interaction value well agrees with what is deduced from the previous study using the 2D periodic boundary condition (V c2 a = 0.212 at T = 0.001 [18]). We note, however, that the real situation is a bit more complicated because the merging happens separately in the conduction and valence bands in α-(BEDT-TTF) 2 I 3 reflecting the tilt of the Dirac cones; in Fig.…”

Section: A Local Electronic Structures and The Massive Dirac Electrosupporting

confidence: 90%

“…The peak is ascribed to a direct transition between different van Hove singularities in the conduction and valence bands, locating at a time reversal invariant momentum (TRIM). Similar structures have been observed in the previous study using the 2D periodic boundary condition [18]. A remarkable difference found in the present cylindrical model is the additional bump at low energy with a kink at ω DW 6 meV, which only appears for the (AA -AA ) symmetric pattern.…”

Section: Optical Conductivity and Optical Gap ∆Osupporting

confidence: 90%

“…action V c a = 0.197. This divergence signals the opening of a gap via spontaneous charge ordering, in line with our recent results using the 2D periodic boundary condition [18]. These data are contrasted to the (AA -AA ) symmetric pattern [ Fig.…”

Section: B Temperature Dependence Of the Resistivity And The Transposupporting

confidence: 89%

“…The charge-ordering gap 2∆ ρ (V a ) starts to open at V a = V c a and continues to develop almost linearly for V a > V c a . For the (AA -BC) asymmetric pattern the gap size agrees with that for the 2D periodic boundary condition [18] since the bulk appearance of charge order results in a unique definition of the gap. In contrast, the evolution of 2∆ ρ (V a ) for the (AA -AA ) symmetric pattern shows a marked difference for certain types of fits.…”

Section: B Temperature Dependence Of the Resistivity And The Transposupporting

confidence: 70%

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Domain wall conductivity with strong Coulomb interaction of two-dimensional massive Dirac electrons in the organic conductor α−(BEDT−TTF)2I3

2019

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Motivated by the results of recent transport and optical conductivity studies, we propose a semiinfinite two-dimensional lattice model for interacting massive Dirac electrons in the pressurized organic conductor α-(BEDT-TTF)2I3, and address the problem of domain wall conductivity in a charge-ordered insulating phase under realistic experimental conditions. Using the extended Hubbard model at a mean field level, we present results of extensive numerical studies around the critical region of the model, reporting on the resistivity and optical conductivity calculated by means of the Nakano-Kubo formula. We find that the activation gap extracted from the resistivity data can be much smaller than the optical gap in the critical region, which is induced by metallic conduction along an one-dimensional domain wall emerging at the border of two charge-ordered ferroelectric regions with opposite polarizations. The data are consistent with the observed transport gap in real α-(BEDT-TTF)2I3 samples that is reduced remarkably faster than the optical gap upon suppressing charge order with pressure. Our optical conductivity also reveals an additional shoulder-like structure at low energy inside the gap, which is argued to be directly relevant to the metallic bound states residing on the domain wall. arXiv:1904.03884v2 [cond-mat.mes-hall]

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Section: A Local Electronic Structures and The Massive Dirac Electrosupporting

confidence: 90%

Section: Optical Conductivity and Optical Gap ∆Osupporting

confidence: 90%

Section: B Temperature Dependence Of the Resistivity And The Transposupporting

confidence: 89%

Section: B Temperature Dependence Of the Resistivity And The Transposupporting

confidence: 70%

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Domain wall conductivity with strong Coulomb interaction of two-dimensional massive Dirac electrons in the organic conductor α−(BEDT−TTF)2I3

2019

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“…The contribution of Rabaça et al and Prokhorova et al considers structural disorder [12][13][14]. The existence of Dirac-like electrons in α-(BEDT-TTF) 2 I 3 is another topic that has attracted interest for more than a decade, from a theoretical side [15] as well as from the side of applications [16]. Pressure-dependent experiments are also important for the one-dimensional TMTTF salts, in order to study the charge and anion ordering [17,18].…”

mentioning

confidence: 99%

Advances in Organic Conductors and Superconductors

Dressel¹

2018

Crystals

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Crystalline conductors and superconductors based on organic molecules are a rapidly progressing field of solid-state science, involving chemists, and experimental and theoretical physicists from all around the world. In focus are solids with electronic properties governed by delocalized π-electrons. Although carbon-based materials of various shades have gained enormous interest in recent years, charge transfer salts are still paradigmatic in this field. Progress in molecular design is achieved via tiny but ingenious modifications, as well as by fundamentally different approaches. The wealth of exciting physical phenomena is unprecedented and could not have been imagined when the field took off almost half a century ago.Organic low-dimensional conductors are prime examples of Luttinger liquids; they exhibit a tendency toward Fermi surface instabilities, but can also be tuned across a dimensionality-driven phase diagram like no other system. Superconductivity comes at the border to ordered phases in the spin and charge sectors, and, at high fields, the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state is well established. The interplay between charge and magnetic order is still under debate, but electronic ferroelectricity is well established. After decades of intense research, the spin liquid state was first discovered in organic conductors when the amount of geometrical frustration and electronic correlations is just right. They drive the metal and superconductor into an insulating Mott state, solely via electron-electron interactions. However, what do we know about the effect of disorder? Can we tune the electronic properties by pressure, by light, or by field? Research is still addressing basic questions, but devices are not out of reach. These are currently open questions, as well as hot and timely topics.Although the superconducting transition temperature remains rather moderate for organic materials, the questions addressed are of fundamental importance, and for several topics molecular conductors are by far the best model system for detailed investigations. The spatial modulation of the superconducting order parameter in the Fulde-Ferrell Larkin-Ovchinikov state is certainly one of them [1,2]. The conceptional paper by Otsuka et al. reviews current ideas on the design of a spin-frustrated Mott insulator and points towards future developments in quantum spin liquids [3]. No question, this exciting research topic has placed organic crystals again at the forefront of solid-state physics. The class of β -Et x Me 4−x Z[Pd(dmit) 2 ] 2 with Z = P, As, Sb and x = 0, 1, 2 is a topic of the paper from Ueda et al. [4]. A completely new view on the structural properties of κ-(BEDT-TTF) 2 Cu 2 (CN) 3 is given by Foury-Leylekian and collaborators [5], who found that the compound contains two non-equivalent dimers in the unit cell and charge disproportionation between the dimers. Here, simple facts, assumed to be settled for decades, were revisited, such as the symmetry of a crystal; this laid new ground for the re-interpreta...

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High-Density, Nonvolatile, Flexible Multilevel Organic Memristor Using Multilayered Polymer Semiconductors

Sharma,

Pandey,

Nagamatsu

et al. 2024

ACS Appl. Mater. Interfaces

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Nonvolatile organic memristors have emerged as promising candidates for next-generation electronics, emphasizing the need for vertical device fabrication to attain a high density. Herein, we present a comprehensive investigation of highperformance organic memristors, fabricated in crossbar architecture with PTB7/Al-AlO x -nanocluster/PTB7 embedded between Al electrodes. PTB7 films were fabricated using the Unidirectional Floating Film Transfer Method, enabling independent uniform film fabrication in the Layer-by-Layer (LbL) configuration without disturbing underlying films. We examined the charge transport mechanism of our memristors using the Hubbard model highlighting the role of Al-AlO x -nanoclusters in switching-on the devices, due to the accumulation of bipolarons in the semiconducting layer. By varying the number of LbL films in the device architecture, the resistance of resistive states was systematically altered, enabling the fabrication of novel multilevel memristors. These multilevel devices exhibited excellent performance metrics, including enhanced memory density, high on−off ratio (>10 8 ), remarkable memory retention (>10 5 s), high endurance (87 on−off cycles), and rapid switching (∼100 ns). Furthermore, flexible memristors were fabricated, demonstrating consistent performance even under bending conditions, with a radius of 2.78 mm for >10 4 bending cycles. This study not only demonstrates the fundamental understanding of charge transport in organic memristors but also introduces novel device architectures with significant implications for high-density flexible applications.

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Optical Conductivity in a Two-Dimensional Extended Hubbard Model for an Organic Dirac Electron System α-(BEDT-TTF)2I3

Cited by 9 publications

References 41 publications

Domain wall conductivity with strong Coulomb interaction of two-dimensional massive Dirac electrons in the organic conductor α−(BEDT−TTF)2I3

Domain wall conductivity with strong Coulomb interaction of two-dimensional massive Dirac electrons in the organic conductor α−(BEDT−TTF)2I3

Advances in Organic Conductors and Superconductors

High-Density, Nonvolatile, Flexible Multilevel Organic Memristor Using Multilayered Polymer Semiconductors

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