Low Energy Electrodynamics in Solids 2012

Low energy electrodynamics of the Kondo-lattice antiferromagnet CeCu$_2$Ge$_2$

23 Jul 2012, 20:00

2h

Fountain Court (Embassy Suites Napa Valley)

Board: 18

Poster Heavy Fermions Poster Session 1

Speaker

Grace Bosse (The Institute for Quantum Matter, Department of Physics and Astronomy, Johns Hopkins University)

Description

Grace Bosse, The Institute for Quantum Matter, Department of Physics and Astronomy, Johns Hopkins University L. Bilbro, The Institute for Quantum Matter, Department of Physics and Astronomy, Johns Hopkins University R. Valdes Aguilar, The Institute for Quantum Matter, Department of Physics and Astronomy, Johns Hopkins University L. Pan, The Institute for Quantum Matter, Department of Physics and Astronomy, Johns Hopkins University W. Liu, The Institute for Quantum Matter, Department of Physics and Astronomy, Johns Hopkins University A.V. Stier, The Institute for Quantum Matter, Department of Physics and Astronomy, Johns Hopkins University Y. Li, Department of Physics and Fredrick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign J. Eckstein, Department of Physics and Fredrick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign N.P. Armitage, The Institute for Quantum Matter, Department of Physics and Astronomy, Johns Hopkins University We present time-domain THz spectroscopy data of a thin film of the heavy fermion compound CeCu$_2$Ge$_2$. Measurements to obtain the frequency dependent complex conductivity were taken as a function of temperature down to temperatures below the onset of magnetic order. At low temperatures a narrow Drude-like peak forms, which is likely associated with the heavy fermion or spin density wave state. Using this data in conjunction with DC resistivity measurements and Fourier transformed infrared reflectivity data, we obtain the frequency dependence of the scattering rate and the mass renormalization through an extended Drude model analysis. At lowest temperatures, an effective mass of almost 80 times the band mass is observed, which is consistent with reported specific heat measurements. The persistence and further development of the heavy fermion state well into the antiferromagnetic state, which challenges the conventional understanding of the low temperature competition between Kondo screening and the Ruderman-Kittel-Kasuya-Yosida interaction, will be discussed.