Metal-Insulator Transitions

Investigations of charge dynamics at the metal-insulator transitions provide important information about the physical mechanism of this phenomena. One of the open problems in this field is to follow the transformation of the response of localized carriers (Lorentzian-like) to the Drude-response of the free carriers in the metallic state.

Broadband conductivity of magnetite at the Verwey transition3
Frequency dependence of the conductivity and the dielectric constant of magnetite above and below TV = 123 K. Symbols below 40 cm-1 and solid lines above 30 cm-1 represent the experimental data, dashed lines - model calculations. The main contribution to the model calculations is given by the hopping term below TV and a Drude-conductivity above TV.
Scaling of conductivity and dielectric constant at the metal-insulator transition
Dielectric permittivity of La1-xSrxMnO3 plotted as function of conductivity with the temperature as tuning parameter and for B = 0. The dashed line indicates a linear scaling between permittivity and conductivity with the characteristic frequency of 6 THz.

Selected publications

  • A. Pimenov, M. Biberacher, D. Ivannikov, A. Loidl, A. A. Mukhin, Yu. G. Goncharov, and A. M. Balbashov
    Scaling of terahertz conductivity at the metal-insulator transition in doped manganites
    Phys.Rev. B 73, 220407(R) (2006)
  • A. Pimenov, S. Tachos, T. Rudolf, A. Loidl, D. Schrupp, R. Claessen, and V. A. M. Brabers
    Terahertz Conductivity at the Verwey Transition in Magnetite
    Phys.Rev. B, 72, 035131 (2005)
  • N. N. Kovaleva, A. V. Boris, C. Bernhard, A. Kulakov, A. Pimenov, A. M. Balbashov, G. Khaliullin, and B. Keimer
    Spin-Controlled Mott-Hubbard Bands in LaMnO3 Probed by Optical Ellipsometry
    Phys.Rev. Lett. 93, 147204 (2004)
  • J. Sichelschmidt, M. Paraskevopoulos, M. Brando, R. Wehn, D. Ivannikov, F. Mayr, K. Pucher, J. Hemberger, A. Pimenov, H.-A. Krug von Nidda, P. Lunkenheimer, V. Yu. Ivanov, A. A. Mukhin, A. M. Balbashov and A. Loidl
    Magnetic, electronic, dielectric and optical properties of Pr(Ca:Sr)MnO3
    Eur. Phys. J. B 20, 7 (2001)
  • A. Pimenov, Ch. Hartinger, A. Loidl, A. A. Mukhin, V. Yu. Ivanov, and A. M. Balbashov
    Itinerant versus localized transport  in La1-xSrxMnO3 for x<=0.175
    Phys. Rev. B 59, 12419 (1999)