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Peter Hirschfeld
Professor
Department of Physics
University of Florida

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Phz7427 - Spring 2013

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Peter Hirschfeld 8/18/10


 

Current research highlights



    

  Fe-based superconductors The new Fe-based pnictide and chalcogenide superconductors have Tc's of up to 55K and are more 3D than the cuprates. (Already confused? You're not the only one.) What makes the electrons form pairs? Left top: schematic superconducting gap function on various Fermi surface sheets, both conventional (left) and sign-changing (right). Left bottom: phase diagram of generic Fe-pnictide material with calculated gap structure from spin fluctuation theory. Gap strength and sign indicated by false color. From Hirschfeld, Korshunov and Mazin, Rep. Prog. Phys. 74, 124508 (2011)
Defects in correlated systems   Impurities induce magnetic droplets in strongly correlated systems (see Rev. Mod. Phys. 81, 45 (2009)), cover photo shown at right).  The overlap of these droplets leads to long-range antiferromagnetic order, an "order by disorder" phenomenon enhanced by d-wave superconductivity. Recently we showed how fluctuating spin order is "frozen" by impurities, strongly resembling puzzling behavior observed in cuprate superconductors. See Phys. Rev. Lett. 105, 147002 (2010).  
 
 


 

  Grain boundary transport  For many years an exponential decrease of the critical current at grain boundaries of cuprate high-Tc superconductors as a function of misorientation angle has been observed.  It is believed that this effect limits the performance of high-Tc power transmission applications.  In  Nat. Phys. 6, 609 (2010) , we present a solution for the origin of this effect via modelling of the charge inhomogeneity at the boundary.  Left: YBCO grain boundary reconstructed by molecular dynamics. See also News and Views .