Electric Conductivity of the Zero-Gap Semiconducting State in α-(BEDT-TTF)<sub>2</sub>I<sub>3</sub>Salt

Katayama, Shinya; Kobayashi, Akito; Suzumura, Yoshikazu

doi:10.1143/jpsj.75.023708

Cited by 55 publications

(53 citation statements)

References 17 publications

(30 reference statements)

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“…The existence of the ZGS with the massless Dirac fermions was found in α-(BEDT-TTF) 2 I 3 [30,31], and the electronic properties have been investigated theoretically [20,28,29,34]. α-(BEDT-TTF) 2 I 3 is a unique material among several materials with Dirac fermions, i.e.…”

Section: Discussionmentioning

confidence: 99%

“…indicates the metal owing to the overlap of the conduction and valence bands. In the ZGS, the gap is always zero, indicating the robustness of the ZGS with varying pressure [31]. If the inversion symmetry is retained under some change in the transfer energies, the point degeneracy of those bands is topologically protected, while the contact points move in the first Brillouin zone.…”

Section: Electronic States Under Pressurementioning

confidence: 99%

“…The chemical potential is taken as zero. Figure 6 shows the energy dispersion of the conduction band ξ 1 and the valence band ξ 2 for U = 0.4, V a = 0.17, and V b = 0.05, where the lattice constant is taken as a = 1 [31]. The chemical potential coincides with the contact point at T = 0.…”

Section: Electronic States Under Pressurementioning

confidence: 99%

“…The density of states (DOS) in the unconventional state is proportional to | | with being the energy measured from the chemical potential. By extending this calculation, the energy dispersion of such electronic state is investigated theoretically using the transfer energies estimated from the experimental data under uniaxial pressure [27], then the Dirac cone dispersion is predicted [30,31]. It is the ZGS where the chemical potential coincides with the contact points of two cones facing each other.…”

Section: Introductionmentioning

confidence: 99%

“…The puzzle in the transport phenomena has been studied theoretically on the basis of the ZGS concept. The weak temperature dependence of resistivity is demonstrated using total band structure [54] and the relation between the quantum conductance in graphene [43] is discussed. Recently, a sharp but continuous change of the sign of the Hall coefficient has been observed at low temperatures [24].…”

Section: Introductionmentioning

confidence: 99%

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Theoretical study of the zero-gap organic conductor α-(BEDT-TTF)₂I₃

Kobayashi

Katayama

Suzumura

2009

Science and Technology of Advanced Materials

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The quasi-two-dimensional molecular conductor α-(BEDT-TTF) 2 I 3 exhibits anomalous transport phenomena where the temperature dependence of resistivity is weak but the ratio of the Hall coefficient at 10 K to that at room temperature is of the order of 10 4 . These puzzling phenomena were solved by predicting massless Dirac fermions, whose motions are described using the tilted Weyl equation with anisotropic velocity. α-(BEDT-TTF) 2 I 3 is a unique material among several materials with Dirac fermions, i.e. graphene, bismuth, and quantum wells such as HgTe, from the view-points of both the structure and electronic states described as follows. α-(BEDT-TTF) 2 I 3 has the layered structure with highly two-dimensional massless Dirac fermions. The anisotropic velocity and incommensurate momenta of the contact points, ±k 0 , originate from the inequivalency of the BEDT-TTF sites in the unit cell, where ±k 0 moves in the first Brillouin zone with increasing pressure. The massless Dirac fermions exist in the presence of the charge disproportionation and are robust against the increase in pressure. The electron densities on those inequivalent BEDT-TTF sites exhibit anomalous momentum distributions, reflecting the angular dependences of the wave functions around the contact points. Those unique electronic properties affect the spatial oscillations of the electron densities in the vicinity of an impurity. A marked behavior of the Hall coefficient, where the sign of the Hall coefficient reverses sharply but continuously at low temperatures around 5 K, is investigated by treating the interband effects of the magnetic field exactly. It is shown that such behavior is possible by assuming the existence of the extremely small amount of electron doping. The enhancement of the orbital diamagnetism is also expected. The results of the present research shed light on a new aspect of Dirac fermion physics, i.e. the emergence of unique electronic properties owing to the structure of the material.

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Section: Discussionmentioning

confidence: 99%

Section: Electronic States Under Pressurementioning

confidence: 99%

Section: Electronic States Under Pressurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Theoretical study of the zero-gap organic conductor α-(BEDT-TTF)₂I₃

Kobayashi

Katayama

Suzumura

2009

Science and Technology of Advanced Materials

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Lorentz‐Boost‐Driven Magneto‐Optics in a Dirac Nodal‐Line Semimetal

et al. 2022

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Optical response of crystalline solids is to a large extent driven by excitations that promote electrons among individual bands. This allows one to apply optical and magneto‐optical methods to determine experimentally the energy band gap —a fundamental property crucial to our understanding of any solid—with a great precision. Here it is shown that such conventional methods, applied with great success to many materials in the past, do not work in topological Dirac semimetals with a dispersive nodal line. There, the optically deduced band gap depends on how the magnetic field is oriented with respect to the crystal axes. Such highly unusual behavior is explained in terms of band‐gap renormalization driven by Lorentz boosts which results from the Lorentz‐covariant form of the Dirac Hamiltonian relevant for the nodal line at low energies.

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Fano Resonances for Tilted Linear and Quadratic Band Touching Dispersions in a Harmonically Driven Potential Well

Gregefalk,

Black‐Schaffer,

Nag

2023

Annalen der Physik

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Considering models with tilted linear and quadratic band touching dispersions, the effect of the transverse linear tilt on the transmission spectra is analyzed through a harmonically driven potential well oriented longitudinally. Employing the Floquet scattering matrix formalism, Fano resonances are found as an outcome of matching between the Floquet sidebands and quasi‐bound states, where the tilt renormalizes their energies and wave vectors. It is found that the Fano resonance energy decreases (increases) for linear (quadratic) band touchings as the magnitude of the transverse momentum increases, indicating a distinct signature of the underlying band dispersion in the transmission profile. The sign of the product of the transverse momentum and the tilt also determines the relative shift in the Fano resonance energy with respect to the untilted case for both band dispersions, suggesting a possible tunability of the Fano resonance for tilted systems. Importantly, the tilt strength can also be directly determined by measuring the Fano resonance energy as function of the transverse momenta direction. The shot noise spectra and their differential property are further studied where an inflection region and undulation, respectively, is found around the Fano resonance energy. Interestingly, differential shot noise and transmission spectra both qualitatively behave in a similar fashion and might thus serve as important observables for future experiments on driven solid‐state systems.

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Electric Conductivity of the Zero-Gap Semiconducting State in α-(BEDT-TTF)₂I₃Salt

Cited by 55 publications

References 17 publications

Theoretical study of the zero-gap organic conductor α-(BEDT-TTF)₂I₃

Theoretical study of the zero-gap organic conductor α-(BEDT-TTF)₂I₃

Lorentz‐Boost‐Driven Magneto‐Optics in a Dirac Nodal‐Line Semimetal

Fano Resonances for Tilted Linear and Quadratic Band Touching Dispersions in a Harmonically Driven Potential Well

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Electric Conductivity of the Zero-Gap Semiconducting State in α-(BEDT-TTF)2I3Salt

Cited by 55 publications

References 17 publications

Theoretical study of the zero-gap organic conductor α-(BEDT-TTF)2I3

Theoretical study of the zero-gap organic conductor α-(BEDT-TTF)2I3

Lorentz‐Boost‐Driven Magneto‐Optics in a Dirac Nodal‐Line Semimetal

Fano Resonances for Tilted Linear and Quadratic Band Touching Dispersions in a Harmonically Driven Potential Well

Contact Info

Product

Resources

About

Electric Conductivity of the Zero-Gap Semiconducting State in α-(BEDT-TTF)₂I₃Salt

Theoretical study of the zero-gap organic conductor α-(BEDT-TTF)₂I₃

Theoretical study of the zero-gap organic conductor α-(BEDT-TTF)₂I₃