Alexey B. Kuzmenko - Optics @ Unige - Université de Genève

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Couplings between charge, spin, orbital and lattice degrees of freedom in solids Superconductivity Most significant scientific results Discovery of a giant Faraday rotation (up to 6 degrees) in single atomic graphene layer on SiC and its explanation as due to the cyclotron resonance [I. Crassee et al. arxiv: 1007:5286, submitted to Nature Physics]. First observation of a strong doping dependence of the intensity and the Fano asymmetry of the infrared phonon G-peak in electrostatically gated bilayer graphene. An explanation of this effect using the theories of Fano and Rice.This can be used for a contact-free characterization of graphene [A.B.Kuzmenko et al., Phys. Rev. Lett. 103, 116804 (2009); E.Cappelluti et al., Phys. Rev. B 82 041402(R) (2010)]. Optical measurement of the electric-field induced bandgap in gated bilayer graphene [A.B. Kuzmenko et al., Phys. Rev. B 80 165406 (2009)]. The existence of this gap is extremely important for applications of graphene in electronics. Our paper appeared simultaneously with two other independent papers reporting similar results [K.F. Mak et al. Rev. Lett. 102, 256405 (2009) and Y. Zhang et al.Nature 459, 820 (2009)]. However, in contrast to other papers, we extracted selfconsistently all tight-binding (SWMcC) parameters from the same set of optical data. 2 Experimental demonstration that the optical conductivity of graphite is equal to e / 4h [A.B. Kuzmenko et al., Phys. Rev. Lett. 100, 117401 (2008)], which is the universal value expected for monolayer graphene. In the same paper we predicted that the optical transmission of monolayer graphene should be dependent only on the fine-structure constant: T = 1− πα . This was indeed experimentally found in the group of A.K. Geim [R.R: Nair et al., Science 320, 1308 (2008)]. This universal behaviour is of fundamental importance for the optical applications of graphene. Establishing the two-band nature of the superconductivity in MgB2 using optical measurements [A.B. Kuzmenko et al., Solid State Commun.121, 479 (2002)] and theoretical input [I.I. Mazin et al., Phys. Rev. Lett. 89, 107002 (2002)]. Systematic study of the optical sum rules in a high-temperature superconductor Bi2212 as function of doping [A.B. Kuzmenko et al. Phys. Rev. B. 72, 144503 (2005), F, Carbone et al., Phys. Rev. B. 74, 064510 (2006)]. It was shown that in the optimally and underdoped regime the total Drude weight increases when entering the superconducting state, which implies a possible lowering of the electronic kinetic energy below the SC transition, contrary to the predictions of the BCS theory. However, in the overdoped regime, the BCS-like behaviour is observed. These finding have important implications for the mechanism of superconductivity in the high-Tc cuprates, which is not yet understood. Development of a novel Kramers-Kronig constrained variational method of the analysis of optical spectra [A.B. Kuzmenko, Rev. Sci. Instrum.76, 083108 (2005)], allowing the analysis of a great variety of spectroscopic data. This method I implemented in a freely available program RefFIT [http://optics.unige.ch/alexey/reffit.html], used at present by more the 50 optics groups in the world. Observation of a strong spin-phonon coupling and an anomalous phonon softening in cupric oxide CuO [Phys. Rev. B 63, 094303 (2001)], which was found later to be multiferroic. This material is a parent compound of high-Tc cuprates. It is also widely used in the production of various nanostructures. References
Prof. D. van der Marel, Département de Physique de la Matière Condensée, University of Geneva Quai Ernest-Ansermet 24, 1211 Genève 2, Switzerland Phone: +41 22 3796234 Prof. A.K. Geim, Schuster Building-2.14, The School of Physics and Astronomy The University of Manchester, Manchester, M13 9PL Phone: +44 161 2754120 Prof. D.N. Basov, Department of Physics, University of California, San Diego La Jolla, California Phone: +1 858 822-1211 Guidance of PhD and Master students I. Crassee: 2008-present, PhD student, Univ. of Geneva, Title “Optical spectroscopy of graphene” S. Teitelbaum: 2009, Undergraduate research project, Univ. of Geneva, Title: “Exfoliation of Very thin Films of BSCCO-2212” M. Gueye: 2008-2009, MS student, Univ. of Geneva, Title: “Spectroscopie optique de couches minces d’or pour une large bande de fréquences” D. van Mechelen: 2004-2010, PhD student*, Univ. of Geneva, Title: “Charge and spin electrodynamics of SrTiO3 and EuTiO3 studied by optical spectroscopy” E. van Heumen: 2003-2009, PhD student*, Univ. of Geneva, Title: “Towards a quantitative understanding of the high.Tc phenomenon” V. Guritanu: 2003-2009, PhD student*, Univ. of Geneva, Title: “Optical study of strongly correlated electrons in metals” F. Carbone: 2003-2008, PhD student*, Univ. of Geneva, Title: “Spectroscopic signatures of electronic correlations in superconductors and magnets” I. Santoso: 2003, MS student*, Univ. of Geneva, Title: “Kinetic Energy Pairing in Cuprates” N. Tombros: 2002-2003, MS student, Univ. of Groningen, Title: “Optical transmission of La2xSrxCuO4: a new insight into the interplane conductivity” A. S. Krechetov: 1997-1998, MS student**, P.L. Kapitza Institute: Title: “Optical properties of Basubstituted YBa2Cu3O7-x“ * The main supervisor Prof. D. van der Marel ** The main supervisor Prof. E.A. Tishchenko PhD Thesis Title: “Infrared spectroscopy of CuO and Bi2O3”, Moscow, Russia (2000) Publication statistics (according to Web of Science on 03.09.2010)
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Alexey B. Kuzmenko - Optics @ Unige - Université de Genève

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