Magnetic-field-driven quantum critical behavior in graphite and bismuth

Kopelevich, Y.; Pantoja, J. C. Medina; Silva, Robson R. da; Moehlecke, S.

doi:10.1016/j.aop.2006.04.002

Cited by 4 publications

(5 citation statements)

References 54 publications

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“…30) It is expected that these phenomena are related to the electronic states of the new massless Fermion. The roles of the new terms for z and 0 on the magnetic response are interesting problems.…”

Section: Discussion and Summarymentioning

confidence: 99%

Massless Fermions in Organic Conductor

et al. 2007

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The electronic states in two-dimensional organic conductor -(BEDT-TTF) 2 I 3 have been investigated to show the noticeable property of the massless fermions, i.e., the linear dispersion which exists on the contact point between the conduction band and the valence band. These fermions are well known in bismuth and graphite, where the former are described by the Dirac equation and the latter obeys the Weyl equation corresponding to the massless fermion. In the present study, we show that the effective Hamiltonian describing the massless fermions in -(BEDT-TTF) 2 I 3 contains intrinsically new terms of Pauli matrices z and 0 in addition to the Weyl equation which consists of x and y . The new massless fermions are robust against the charge disproportionation, and induce the anomalous momentumdependence in the charge density.

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Section: Discussion and Summarymentioning

confidence: 99%

Massless Fermions in Organic Conductor

et al. 2007

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“…The 2 × 2 partial differential equation system ( 8) is an alternative way to describe the electron dynamics in strained graphene with deformed Dirac cones and in the presence of a nonuniform magnetic field from the anisotropy parameters with a spatial dependence. If we know the exact form of a(x, y) and b(x, y) from the dispersion relation or the Fermi velocity, it is possible to obtain the LLs solving the equation system (8). When an inhomogeneous unidirectional strain is applied, these functions must depend only on x (y) due to the translational symmetry on y (x).…”

Section: Landau Levels In Strained Graphenementioning

confidence: 99%

“…In an ordinary conductor, the energy of the LLs have a linear dependence with the quantization integer n, as (n + 1/2)B. However, in graphene the LLs spectrum is quantized according to √ nB [7][8][9][10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Landau levels in uniaxially strained graphene: A geometrical approach

et al. 2015

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The effect of strain on the Landau levels (LLs) spectra in graphene is studied, using an effective Dirac-like Hamiltonian which includes the distortion in the Dirac cones, anisotropy and spatial-dependence of the Fermi velocity induced by the lattice change through a renormalized linear momentum. We propose a geometrical approach to obtain the electron's wave-function and the LLs in graphene from the Sturm-Liouville theory, using the minimal substitution method. The coefficients of the renormalized linear momentum are fitted to the energy bands, which are obtained from a Density Functional Theory (DFT) calculation. In particular, we evaluate the case of Dirac cones with an ellipsoidal transversal section resulting from uniaxially strained graphene along the armchair (AC) and zig-zag (ZZ) directions. We found that uniaxial strain in graphene induces a contraction of the LLs spectra for both strain directions. Also, is evaluated the contribution of the tilting of Dirac cone axis resulting from the uniaxial deformations to the contraction of the LLs spectra.

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“…The motions of electrons obey the Weyl equation that was used for neutrino, although the velocity is of the order of 10 −3 of the light velocity [36][37][38]. Anomalous properties in transport phenomena, i.e.…”

Section: Introductionmentioning

confidence: 99%

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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Magnetic-field-driven quantum critical behavior in graphite and bismuth

Cited by 4 publications

References 54 publications

Massless Fermions in Organic Conductor

Massless Fermions in Organic Conductor

Landau levels in uniaxially strained graphene: A geometrical approach

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

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Magnetic-field-driven quantum critical behavior in graphite and bismuth

Cited by 4 publications

References 54 publications

Massless Fermions in Organic Conductor

Massless Fermions in Organic Conductor

Landau levels in uniaxially strained graphene: A geometrical approach

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

Contact Info

Product

Resources

About

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