FOCUS 

The discovery of high-temperature superconductors (HTSC) has challenged many well-accepted principles of how metals (typically, Fermi liquids) behave. Though showing metallic behavior, these materials have a number of fundamentally anomalous properties that have defied explanation for the last decade. One of the most striking anomalies is the DC Hall effect, where the scattering rate associated with transverse Hall current appears to be fundamentally different from the scattering rate associated with longitudinal current. A rich variety of models is consistent with the DC Hall measurements; however, these models predict different behavior at higher frequencies. Thus, Hall measurements at finite frequencies are essential for determining which models have the most promise for providing a complete understanding of HTSC response. We have extended Hall measurement into the infrared frequency range by using sensitive optical polarization modulation techniques. This novel measurement not only allows a critical test of the proposed models for HTSC materials, but may also shed light on the origin of the unusual properties found in other classes of materials, such as the ruthenates and colossal magnetic resistance oxides, which also show evidence for non­Fermi liquid behavior.

PUBLICATIONS

• M. Quijada, J. Cerne, R. Simpson, H. D. Drew, K. H. Ahn, A. J. Millis, R. Shreekala, R. Ramesh, M. Rajeswari, and T. Venkatesan. Optical conductivity of maganites: Crossover from Jahn-Teller small polaron to coherent transport in the Ferromagnetic state. Phys. Rev. B 58:16093 (1998).
• J. Kono, M. Y. Su, J. Cerne, M. S. Sherwin, S. J. Allen Jr., T. Inoshita, T. Noda, and
  H. Sakaki. Resonant generation of Terahertz optical sidebands from confined magnetoexcitons. Nucl. Instrum. Methods Phys. Res. B 144:115 (1998).
• J. Kono, M. Y. Su, J. Cerne, M. S. Sherwin, S. J. Allen Jr., T. Inoshita, T. Noda, and
  H. Sakaki. Terahertz dynamics in confined magnetoexcitons. Physica B 249:527 (1998).
• J. Cerne, J. Kono, M. S. Sherwin, M. Sundaram, and A. C. Gossard. Near-infrared sideband generation induced by intense far-infrared radiation in GaAs/A1GaAs quantum wells in magnetic fields. Appl. Phys. Lett. 70:3543 (1997).
• J. Cerne, J. Kono, M. S. Sherwin, M. Sundaram, A. C. Gossard, and G. E. W. Baur. Terahertz dynamics of excitons in GaAs/A1GaAs quantum wells. Phys. Rev. Lett. 77:1131 (1996).