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We present measurements of the optical spectra on single crystals of spinel-type compound \cis. This material undergoes a sharp metal-insulator transition at 230 K. Upon entering the insulating state, the optical conductivity shows an…

Strongly Correlated Electrons · Physics 2009-11-10 N. L. Wang , G. H. Cao , P. Zheng , G. Li , Z. Fang , T. Xiang , H. Kitazawa , T. Matsumoto

Recently, $\mathrm{BaSn_2}$ is predicted to be a strong topological insulator by the first-principle calculations. It is well known that topological insulator has a close connection to thermoelectric material, such as $\mathrm{Bi_2Te_3}$…

Materials Science · Physics 2016-12-21 San-Dong Guo , Liang Qiu

We performed far-infrared optical spectroscopy measurements on the heavy fermion compound URu 2 Si 2 as a function of temperature. The light's electric-field was applied along the a-axis or the c-axis of the tetragonal structure. We show…

Strongly Correlated Electrons · Physics 2011-11-17 J. Levallois , F. Lévy-Bertrand , M. K. Tran , D. Stricker , J. A. Mydosh , Y. -K. Huang , D. van der Marel

We present novel infrared optical conductivity data on the three layer high Tc superconductor Bi2Sr2Ca2Cu3O10 at optimal doping. We extend the analysis of an earlier publication, providing a universal scaling function…

Strongly Correlated Electrons · Physics 2011-05-27 D. van der Marel , F. Carbone , A. B. Kuzmenko , E. Giannini

Topological insulators (TIs) have attracted much attention due to their spin-polarized surface and edge states, whose origin in symmetry gives them intriguing quantum-mechanical properties. Robust control over the chemical potential of TI…

Mesoscale and Nanoscale Physics · Physics 2015-10-28 Andrew L. Yeats , Yu Pan , Anthony Richardella , Peter J. Mintun , Nitin Samarth , David D. Awschalom

We have studied the optical properties of four (LaNiO$_3$)$_n$/(LaMnO$_3$)$_2$ superlattices (SL) ($n$=2, 3, 4, 5) on SrTiO$_3$ substrates. We have measured the reflectivity at temperatures from 20 K to 400 K, and extracted the optical…

Strongly Correlated Electrons · Physics 2015-06-24 P. Di Pietro , J. Hoffman , A. Bhattacharya , S. Lupi , A. Perucchi

A topological insulator Bi2Se3 which shows superconducting property due to Cu doping has been studied using high resolution transmission electron microscopy which provides for the first time, the direct evidence of intercalation sites. A…

Materials Science · Physics 2012-03-12 Tanmay Das , Somnath Bhattacharyya , Bhanu Prakash Joshi , A. Thamizhavel , S. Ramakrishnan

We study disorder effects on the surface states of the topological insulator Bi$_2$Se$_3$ close to the topologically protected crossing point. Close to charge neutrality, local fluctuations in carrier density arising from the random charged…

Mesoscale and Nanoscale Physics · Physics 2012-06-08 S. Adam , E. H. Hwang , S. Das Sarma

We demonstrate that the terahertz/infrared radiation induced photogalvanic effect, which is sensitive to the surface symmetry and scattering details, can be applied to study the high frequency conductivity of the surface states in…

Journal ref.: J. Phys.: Condens. Matter 25, 065602 (2013): We investigated the optical reflectivity of the heavy-fermion metal CeCu2Si2 in the energy range 3 meV - 30 eV for temperatures between 4K - 300K. The results for the charge…

Strongly Correlated Electrons · Physics 2013-01-15 J. Sichelschmidt , A. Herzog , H. S. Jeevan , C. Geibel , F. Steglich , T. Iizuka , S. Kimura

A strip of 2D HgTe topological insulator is studied. The same-spin edge states in ideal system propagate in opposite directions on different sides of the strip and do not mix by tunneling. Impurities, edge irregularities, and phonons…

Mesoscale and Nanoscale Physics · Physics 2014-07-24 M. V. Entin , L. I. Magarill

We investigate the optical conductivity of Sr$_{1-x}$Ca$_x$RuO$_3$ across the ferromagnetic to paramagnetic transition that occurs at $x=0.8$. The thin films were grown by metalorganic aerosol deposition with $0 \leq x \leq 1$ onto…

Strongly Correlated Electrons · Physics 2016-06-09 Diana Geiger , Uwe S. Pracht , Martin Dressel , Jernej Mravlje , Melanie Schneider , Philipp Gegenwart , Marc Scheffler

Nontrivial properties of electronic states in topological insulators are inherent not only to the surface and boundary states, but to bound states localized at structure defects as well. We clarify how the unusual properties of the…

Mesoscale and Nanoscale Physics · Physics 2016-09-19 Vladimir A. Sablikov , Aleksei A. Sukhanov

The optical conductivity along and perpendicular to the planes is calculated assuming strong k-dependence of the scattering rate and the c-axis hopping parameter. Closed analytical expressions for the optical conductivy along these…

Superconductivity · Physics 2009-10-31 D. van der Marel

We measured the in-plane optical conductivity of a nearly optimally doped (Ba,K)Fe2As2 single crystal with Tc = 39.1 K. Upon entering the superconducting state the optical conductivity below ~20 meV vanishes, strongly suggesting a fully…

Superconductivity · Physics 2015-01-09 Y. M. Dai , B. Xu , B. Shen , H. H. Wen , X. G. Qiu , R. P. S. M. Lobo

We report a transport study of ultrathin Bi2Se3 topological insulators with thickness from one quintuple layer to six quintuple layers grown by molecular beam epitaxy. At low temperatures, the film resistance increases logarithmically with…

We apply a topological material design concept for selecting a bulk topology of 3D crystals by different van-der-Waals stacking of 2D topological insulator layers, and find a bismuth halide Bi4Br2I2 to be an ideal weak topological insulator…

We report on the effect of exposure to atmospheric conditions on the THz conductivity of thin films of the topological insulator Bi$_2$Se$_3$. We find: 1) two contributions of mobile charge carriers to the THz conductivity immediately after…

Strongly Correlated Electrons · Physics 2013-09-05 R. Valdés Aguilar , L. Wu , A. V. Stier , L. S. Bilbro , M. Brahlek , N. Bansal , S. Oh , N. P. Armitage

Critical thermoelectric parameters including Seebeck coefficient, electrical conductivity, thermal conductivity and figure of merit ZT of one-dimensional coaxial Bi2Te3/Sb2Te3 nanocomposite were modeled by following the single carrier…

Materials Science · Physics 2011-01-31 Qilin Gu

The optical conductivity of the one-band Hubbard model is calculated using the 'Dynamical Cluster Approximation' implementation of dynamical mean field theory for parameters appropriate to high temperature copper-oxide superconductors. The…

Strongly Correlated Electrons · Physics 2009-10-29 Nan Lin , Emanuel Gull , A. J. Millis