Effects of disorder on the physical properties of organic superconductors

• Applicant: Professor Dr. Reinhold Oppermann
• Subject Area: Theoretical Condensed Matter Physics
• Term: from 2011 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 195285870

• Final Report Year: 2015

Final Report Abstract

In this project research was carried out on effects of quenched disorder in organic superconductors. Some of the new results for quasi-2D organic superconductors were successfully compared with recent experiments, so that they provide a possible explanation. New experiments were suggested too. The role of realistic types of spatially anisotropic disorder and also anisotropic superconductivity were analyzed by means of standard techniques, and led to measurable results for example of the critical temperature and its reduction by increasing disorder. The problem of glassy order was not addressed due to lack of time and obviously necessary more refined techniques and necessary extensions towards anisotropic order parameters. Also studied was a quantum mechanical situation, a rather complicated multiple interaction problem of spin orbit interactions of Rashba and Dresselhaus type in the presence of special magnetic fields. The derived differential equations were solved approximately, and degeneracy lifting by means of Rashba- and Dresselhausinteractions were found to lead an instable regime with negative conductance. In a subsequent work, as well the new problem of particular spin currents in a field theoretic formulation was examined.

Publications

• JETP Lett. 91, 570 (2010). Critical disorder effects in Josephson-couled quais-onedimensional superconductors
  E. Nakhmedov, R. Oppermann
  
• Phys. Rev. B 81, 134511 (2010). Disorder-driven superconductor-normal metal phase transition in quasi-onedimensional organic conductors
  E. Nakhmedov, R. Oppermann
  
• Jap. J. Appl. Phys. 50, 05FE03 (2011). Spin-orbit interactions in a quasi-twodimensional electron gas with finite thickness
  E. Nakhmedov, O. Alekperov, R. Oppermann
  
• Phys. Rev. B 83, 153416 (2011). Negative differential resistance in a finite-thickness quasi-twodimensional electron gas mediated by spin-orbit interactions
  E. Nakhmedov, O. Alekperov, R.Oppermann
  
• Europ. Phys. Journal B 85, 298 (2012). Interplay of Rashba- and Dresselhaus spin-orbit interactions in a quasi-twodimensional electron gas of finite thickness under inplane magetic fields
  E. Nakhmedov, O. Alekperov
  (See online at https://doi.org/10.1140/epjb/e2012-30333-6)
• Phys. Rev. B 85, 153302 (2012). Out-of-plane equilibrium spin current in a quasi-twodimensional electron gas under in-plane magnetic field
  E. Nakhmedov, O. Alekperov
  (See online at https://doi.org/10.1103/PhysRevB.85.153302)
• Phys. Rev. B 86, 214513 (2012). Effects of randomness on the critical temperature in quasi-twodimensional organic superconductors
  E. Nakhmedov, O. Alekperov, R. Oppermann
  (See online at https://doi.org/10.1103/PhysRevB.86.214513)
• Phys. Rev. B89, 195445 (2014). Zero-energy Majorana states in a one-dimensional quantum wire with charge density wave instability
  E. Nakhmedov, O.Alekperov
  (See online at https://doi.org/10.1103/PhysRevB.89.195445)