arXiv 1502.070722015-02cond-mat.mes-hall

Magneto-optics of quasi-relativistic electrons in tilted Dirac cones in graphene and $α$-(BEDT-TTF)$_2$I$_3$

Judit Sári, Mark O. Goerbig, Csaba Toke

备注：: 8 pages, 7 figures
发表信息：: Phys. Rev. B 92, 035306 (2015)

英文摘要：

Massless Dirac fermions occur as low-energy modes in several quasi-two-dimensional condensed matter systems such as graphene, the surface of bulk topological insulators, and in layered organic semiconductors. When the rotational symmetry in such systems is reduced either by an in-plane electric field or an intrinsic tilt of the Dirac cones, the allowed dipolar optical transitions evolve from a few selected transitions into a wide fan of interband transitions. We show that the Lorentz covariance of the low-energy carriers allows for a concise analysis of the emerging magneto-optical properties. We predict that infrared absorption spectra yield quantitative information on the tilted Dirac cone structure in organic compounds such as $α$-(BEDT-TTF)$_2$I$_3$.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

阅读原文

阅读 PDF ↗

arXiv 页面 ↗HTML 原文 ↗

本文内容

英文摘要相关论文

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

继续探索

相关论文

Edge states in the three-quarter filled system, $α$-(BEDT-TTF)$_2$I$_3$

We study the edge states in the two-dimensional conductor $α$-(BEDT-TTF)$_2$I$_3$ theoretically. We show that the Dirac points and the edge states appear at the 3/4 and 1/4 filling as well as the half filling, due to four sites in the unit cell. This situation is in contract with the graphene, where the Dirac points and the edge states appear only at the half filling case. It is shown that the localization length of the edge states can become very large.

2011-04-22cond-mat.mes-hall

Pressure effects on Dirac fermions in α-(BEDT-TTF)2I3

We investigate the pressure effect on the layered Dirac fermion system, which is realized in quasi-two-dimensional organic compound α-(BEDT-TTF)2I3. The trajectory of the contact points is investigated using the tight-binding model with the transfer integrals determined by X-ray diffraction experiments. Vanishing of the Dirac fermion spectrum, opening of the gap, and pressure dependence of inter-layer magnetoresistance are discussed.

2011-08-03cond-mat.mes-hall

Anisotropic spin motive force in multi-layered Dirac fermion system, $α$-(BEDT-TTF)$_2$I$_3$

We investigate the anisotropic spin motive force in $α$-(BEDT-TTF)$_2$I$_3$, which is a multi-layered massless Dirac fermion system under pressure. Assuming the interlayer antiferromagnetic interaction and the interlayer anisotropic ferromagnetic interaction, we numerically examine the spin ordered state of the ground state using the steepest descent method. The anisotropic interaction leads to the anisotropic spin ordered state. We calculate the spin motive force produced by the anisotropic spin texture. The result quantitatively agrees with the experiment.

2015-05-20cond-mat.mes-hall

Magnetoplasmons of the tilted-anisotropic Dirac cone material $α-$(BEDT-TTF)$_2$I$_3$

We study the collective modes of a low-energy continuum model of the quasi-two-dimensional electron liquid in a layer of the organic compound $α-$(BEDT-TTF)$_2$I$_3$ in a perpendicular magnetic field. As testified by zero magnetic field transport experiments and \textit{ab initio} theory, this material hosts both massless and massive low-energy carriers, the former being described by tilted and anisotropic Dirac cones. The polarizability of these cones is anisotropic, and two sets of magnetoplasmon modes occur between any two cyclotron resonances. We show that the tilt of the cones causes a un…

2014-09-09cond-mat.mes-hall

Thermal expansion of organic superconductor k-(D4-BEDT-TTF)2Cu{N(CN)2}Br. Isotopic effect

Linear thermal expansion coefficient (LTEC) of single crystal k-(D4-BEDT-TTF)2Cu[N(CN)2]Br was studied across the crystal layers in the temperature range 2-290 K using the method of precise capacitive dilatometry. Below Tc = 11,6 K the LTEC of the sample had a small negative value, which is apparently due to the transition from the paramagnetic metal in the superconducting state. There was a bend of temperature dependence of the LTEC, which shows broad peak around 40 K and can be attributed to the elastic lattice anomaly around the end-point of Mott boundary. A sharp jump in the LTEC values an…

2017-08-14cond-mat.mes-hall

Existence and merging of Dirac points in $α$-(BEDT-TTF)$_2$I$_3$ organic conductor

We reexamine the existence and stability conditions of Dirac points between valence and conduction bands of 3/4 filled $α$-(BEDT-TTF)$_2$I$_3$ conducting plane. We consider the usual nearest neigbhor tight binding model with the seven transfer energies that depend on the applied pressure. Owing to the four distinct molecules (A, A', B, C) per unit cell of the Bravais lattice, the corresponding Bloch Hamiltonian is a $4\times4$ matrix ${\cal H}({\bm k})$ for each wave vector $\mathbf{k}$ of the Brillouin zone. In most previous works the study of Dirac points was achieved through direct numerica…

2013-03-12cond-mat.mes-hall

更多相关论文收起更多论文

Electric-field-induced lifting of the valley degeneracy in alpha-(BEDT-TTF)_2I_3 Dirac-like Landau levels

The relativistic Landau levels in the layered organic material alpha-(BEDT-TTF)_2I_3 [BEDT-TTF=bis(ethylenedithio)tetrathiafulvalene] are sensitive to the tilt of the Dirac cones, which, as in the case of graphene, determine the low-energy electronic properties under appropriate pressure. We show that an applied inplane electric field, which happens to be in competition with the tilt of the cones, lifts the twofold valley degeneracy due to a different level spacing. The scenario may be tested in infrared transmission spectroscopy.

2009-03-19cond-mat.mes-hallcond-mat.mtrl-sci

Inter-Band Effects of Magnetic Field on Hall Conductivity in Multi Layered Massless Dirac Fermion System $α$-(BEDT-TTF)$_2$I$_3$

We have discovered two-dimensional zero-gap material with a layered structure in the organic conductor $α$-(BEDT-TTF)$_2$I$_3$ under high hydrostatic pressure. In contrast to graphene, the electron-hole symmetry is not good except at the vicinity of the Dirac points. Thus, temperature dependence of the chemical potential, $μ$, plays an important role in the transport in this system. The experimental formula of $μ$ is revealed. We succeeded in detecting the inter-band effects of a magnetic field on the Hall conductivity when $μ$ passes the Dirac point.

2012-01-13cond-mat.mes-hallcond-mat.other

$^{13}$C NMR Study on Zero-Gap State in the Organic Conductor $θ$-(BEDT-TTF)$_{2}$I$_{3}$ under Pressure

We present the results of our $^{13}$C NMR study of the quasi-two-dimensional organic conductor $θ$-(BEDT-TTF)$_2$I$_{3}$ under pressure, which is suggested to be a zero-gap conductor by transport measurements. We found that NMR spin shift is proportional to $T$ and that spin-lattice relaxation rate follows the power law $T^α$ ($α=3 \sim 4$), where $T$ is the temperature. This behavior is consistent with the cone-like band dispersion and provides microscopic evidence for the realization of the zero-gap state in the present material under pressure.

2010-04-15cond-mat.mes-hallcond-mat.mtrl-sci

Tilted anisotropic Dirac cones in quinoid-type graphene and alpha-(BEDT-TTF)_2I_3

We investigate a generalized two-dimensional Weyl Hamiltonian, which may describe the low-energy properties of mechanically deformed graphene and of the organic compound alpha-(BEDT-TTF)_2I_3 under pressure. The associated dispersion has generically the form of tilted anisotropic Dirac cones. The tilt arises due to next-nearest-neighbor hopping when the Dirac points, where the valence band touches the conduction band, do not coincide with crystallographic high-symmetry points within the first Brillouin zone. Within a semiclassical treatment, we describe the formation of Landau levels in a stro…

2008-06-20cond-mat.mes-hallcond-mat.str-el

Magnetic-field-induced dimensional crossover in the organic metal $α$-(BEDT-TTF)$_{2}$KHg(SCN)$_{4}$

The field dependence of interlayer magnetoresistance of the pressurized (to the normal state) layered organic metal $α$-(BEDT-TTF)$_{2}$KHg(SCN)$_{4}$ is investigated. The high quasi-two-dimensional anisotropy, when the interlayer hopping time is longer than the electron mean-free time and than the cyclotron period, leads to a dimensional crossover and to strong violations of the conventional three-dimensional theory of magnetoresistance. The monotonic field dependence is found to change from the conventional behavior at low magnetic fields to an anomalous one at high fields. The shape of Land…

2012-08-20cond-mat.mes-hallcond-mat.other