Goran Karapetrov

Physicist

Materials Science Division; Bldg. 223 Argonne National Laboratory 9700 South Cass Avenue Argonne, Illinois 60439 phone: 630-252-5668 fax: 630-252-7777 email: goran@anl.gov

Education:

• Ph.D., Physics, Oregon State University, Corvallis, Oregon, 1996
• M.S., B.S., Physics, Moscow State University (Lomonosov), Moscow, Russia, 1991

• Physicist, Argonne National Laboratory, 2005
• Assistant Scientist, Argonne National Laboratory, 2000
• Research Scientist, Advanced Microbotics Corp., Portland, OR, 1995

• ISI recognition as lead author of most cited publication in the field of Superconductivity, 2001
• NATO Science for Peace Awards 2000 and 2005
• Sigma Xi physical society award for graduate research accomplishments in high-temperature superconductivity, 1995

• Member of the American Physical Society, MRS, and AVS
• Member of InterNano Advisory board
• DOE - SBIR Program Review Panelist
• Center for Nanoscale Materials - SPM Instrumentation Review Panelist

• Mesoscopic Superconductors and Magnet-Superconductor Hybrid Systems

In mesoscopic materials the free energy of the surface is comparable to or dominates the energy of the bulk, producing a rich variety of new equilibrium states which vary continuously with the surface to volume ratio. Abrikosov vortices in bulk superconductors form a hexagonal lattice, while in mesoscopic structures they form various finite patterns that minimize the surface energy as well as their mutual repulsion. Recent theoretical calculations predict an orderly shell structure for the vortices, similar to the shell structure of electrons in atoms. Scanning tunneling microscopy is an ideal tool for imaging of superconducting order parameter in submicron samples. Spectroscopic STM scans provide unprecedented resolution in imaging the Abrikosov vortices. Novel vortex structures such as vortex shells, giant vortex state, and multiquanta vortices should exist only due to mesoscopic size of the sample. Focus of our study is to examine these vortex phases using STM. The work could have significant impact on both basic science and applicability of nano-engineered superconductors.

• Nanoscale catalysis

The low-temperature polymer electrolyte membrane fuel cell is one of the most promising technologies for the utilization of hydrogen in transportation applications. While the technology is promising, it suffers from i) a significant loss in energy conversion efficiency due to its low cathode catalyst activity, ii) membrane degradation due to peroxide formation during operation, and iii) gradual loss of electrochemically active area due to the limited stability and dissolution of catalysts, resulting in a technology too expensive to compete with internal-combustion engines. Together with a multidisciplinary group at Argonne we have prepared and studied model electrocatalysts, one-dimensional and two-dimensional nanoparticle arrays, and single crystal surfaces for their oxygen reduction reaction and dissolution reaction. We have focused on the role of adjacent facets on the increased electrochemical activity in nanocrystalline Pt.

• Micro-electromechanical Systems (MEMS)

Micromechanical sensors have had dramatic impact on a diverse range of engineering applications. The MEMS-based basic science research tools could enable characterization of materials down to the mesoscopic scale. This is especially useful for investigating materials available only in minute quantities, when operating conditions demand compactness of design, and when local measurements on a single part of a composite system are required. Our focus is on using arrays of cantilever probes for combinatorial-based high throughput parallel sample characterization, differential microcalorimetry, and micromechanical positioners for low-temperature high magnetic field application.

• Unique Activity of Platinum Ad-islands in the CO Electrooxidation Reaction, D. Strmcnik, D. Tripkovic, D. van der Vliet, K.C. Chang, V. Komanicky, H. You, G. Karapetrov, J. Greely, V. Stamenkovic, N. Markovic, accepted in the Journal of the American Chemical Society (2008)
• Effect of Magnetic Impurities on the Vortex Lattice Properties in NbSe₂ Single Crystals, M. Iavarone, R. Di Capua, G. Karapetrov, A.E. Koshelev, D. Rosenmann, H. Claus, C.D. Malliakas, M.G. Kanatzidis, T. Nishizaki, N. Kobayashi, accepted in Physical Review B (2008)
• Tunable Transport in Magnetically Coupled MoGe/Permalloy Hybrids, A. Belkin, V. Novosad, M. Iavarone, J. Fedor, J. Pearson, A. Petrean-Troncalli, G. Karapetrov, Applied Physics Letters 93, 072510 (2008)
• Superconductor - Ferromagnet Bilayers: Influence of Magnetic Domain Structure on Vortex Dynamics, A. Belkin, V. Novosad, M. Iavarone, J. Pearson, G. Karapetrov, Physical Review B - Rapids 77, 180506 (2008)
• Guiding superconducting vortices with magnetic domain walls, V. Vlasko-Vlasov, U. Welp, G. Karapetrov, V. Novosad, D. Rosenmann, M. Iavarone, A. Belkin, and W.-K. Kwok, Physical Review B - Rapids 77, 134518 (2008)
• Probing the Vortex State in CaC6 Using Transverse Field Muon Spin Rotation, A. Kanigel, D. di Castro, A. Keren, P. Postorino, D. Rosenmann, U. Welp, G. Karapetrov, H. Claus, D.G. Hinks, A. Amato, J. C. Campuzano, cond-mat/0803.4513, 2008
• Novel Hall sensors developed for magnetic field imaging systems, V. Cambel, G. Karapetrov, V. Novosad, E. Bartolome, D. Gregusova, J. Fedor, R. Kudela, J. Soltys, J. Magn. Magn. Mat. 316 , 232 (2007)
• Switching of Magnetic Domains in Permalloy Microstructures Using Two-Dimensional Electron Gas, A. Belkin, J. Fedor, P. Pankowski, M. Iavarone, V. Novosad, G. Karapetrov, V. Cambel, D. Gregusova, R. Kudela, Appl. Phys. Lett. 89, 182513 (2006)
• Anisotropy of Magnetization Reversal and Magnetoresistance in Square Arrays of Permalloy Nano-Rings, A. V. Goncharov, A. A. Zhukov, V.V. Metlushko, G. Bordignon, H. Fongohr, C.H. de Groot, J. Unguris, W.C. Uhlig, G. Karapetrov, B. Ilic, P.A.J. de Groot, IEEE Trans. Magn. 42, 2948 (2006)
• Oscillatory Thickness Dependence of the Coercive Field in Magnetic 3D Anti-Dot Arrays, A. A. Zhukov, M.A. Ghanem, A. V. Goncharov, R. Boardman, V. Novosad, G. Karapetrov, H. Fangohr, P.N. Bartlett, P.A.J. de Groot, Appl. Phys. Lett. 88, 062511 (2006)
• Anisotropic Superconducting Phase Diagram of C₆Ca, R. Xie, D. Rosenmann, A. Rydh, H. Claus, G. Karapetrov, W.K. Kwok, U. Welp, Physica C 439, 43 (2006)
• Direct Observation of Vortex Lattice Transitions in Mesoscopic Superconducting Single Crystals, Goran Karapetrov, Jan Fedor, Maria Iavarone, Dan Rosenmann, and W.K. Kwok, Phys. Rev. Lett. 95, p.167002 (2005)
• Imaging of Vortex States in Mesoscopic Superconductors, G. Karapetrov, J. Fedor, M. Iavarone, M.T. Marshall, R. Divan, Appl. Phys. Lett. 87, p.162515 (2005)
• Oscillatory thickness dependence of the coercive field in three-dimensional anti-dot arrays from self-assembly,A. A. Zhukov, A. V. Goncharov, P. A. J. de Groot, M. A. Ghanem, I. S. El-Hallag, P. N. Bartlett, R. Boardman, H. Fangohr, V. Novosad, and G. Karapetrov, Journal of Applied Physics 97, 1, 2005
• Effect of Disorder in MgB₂ Thin Films, M. Iavarone, A. Koshelev, W.K. Kwok, R. DiCapua, R. Vaglio, A. Pogrebnyakov, X.X. Xi, S.I. Lee,  Phys. Rev. B 71, p.214502 (2005)
• MgB₂: Directional Tunneling and Two-Band Superconductivity, M. Iavarone, G. Karapetrov, A. Koshelev, W. K. Kwok, D. Hinks, G. W. Crabtree, W. N. Kang, E.-M. Choi, H. J. Kim, S.-I. Lee, Supercond. Sci. and Tech. 16 p.156 (2003)
• Superconducting Transition and Phase Diagram of Single Crystal MgB2, U. Welp, A. Rydh, G. Karapetrov, W. K. Kwok, G. W. Crabtree, Ch. Marcenat, L. Paulius, T. Klein, J. Marcus, K. H. P. Kim, C. U. Jung, H.-S. Lee, B. Kang, S.-I. Lee, Phys. Rev. B 67 012505 (2003)
• Phase Diagram of Single Crystal MgB2G. Karapetrov, U. Welp, A. Rydh, M. Iavarone, W. K. Kwok, G. W. Crabtree, Ch. Marcenat, L. Paulius, T. Klein, J. Marcus, K. H. P. Kim, C. U. Jung, H.-S. Lee, B. Kang, S.-I. Lee, J. Low Temp. Phys. 131 p.1237-1244 (2003)
• Scanning Tunneling Spectroscopy in MgB2, G. Karapetrov, M. Iavarone, W. K. Kwok, G. W. Crabtree and D. Hinks chapter in the "Studies of High-Tc Superconductors" edited by Narlikar Nova Science Publishers Inc. Chapter 11 in book series: Superconducting Magnesium Diboride, p. 221-228 (2002)
• Two-band Superconductivity in MgB2, M. Iavarone, G. Karapetrov, W.K.Kwok, G.W. Crabtree, D.G. Hinks, W. N. Kang, Eun-Mi Choi, Hyun Jung Kim, Hyeong-Jin Kim and S. I. Lee, Phys. Rev. Lett. 89, p.187002 (2002)
• Scanning Tunneling Spectroscopy in MgB2, G. Karapetrov, M. Iavarone, W.K.Kwok, G.W. Crabtree, and D.G. Hinks, "", Phys. Rev. Lett. 86, p.4374-4377 (2001)

• 6,638,895 - Method for Fabrication of high aspect ratio structure of perovskite material, G. Karapetrov, W.K. Kwok, G.W. Crabtree, M. Iavarone, October 28, 2003
• 5,830,539 - Methods for functionalizing and coating substrates and devices made according to the methods, M. Yan; J.F.W. Keana, G. Karapetrov; C. J.-P. Sevrain, M.N. Wybourne, Nov. 1998