Regensburg 2004 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 7: Korrelierte Elektronen: Schwere Fermionen

TT 7.5: Vortrag

Montag, 8. März 2004, 15:45–16:00, H19

Microwave Conductivity Spectra of Heavy-Fermion UPd₂Al₃ — •Marc Scheffler¹, Martin Dressel¹, M. Jourdan², and H. Adrian² — ¹1. Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart — ²Institut für Physik, Johannes Gutenberg Universität, 55099 Mainz

UPd₂Al₃ is a well-known heavy-fermion system that undergoes antiferromagnetic and superconducting phase transitions at T_N = 14 K and T_c = 2 K, respectively. Previous optical spectroscopy studies [1] of the heavy-fermion nature of this system down to frequencies of about 1 cm⁻¹ (= 30 GHz) showed the influence of heavy-fermion as well as magnetic characteristics and in particular revealed a well-pronounced pseudogap at low frequencies (below 3 cm⁻¹) that was attributed to magnetic correlations. Thus the optical conductivity at even lower frequencies is of notable interest because there the Drude roll-off (the high-frequency characteristic of a metal) remained hidden at extremely low frequencies.
Using a recently developed cryogenic broadband microwave spectrometer employing the Corbino geometry we have studied the complex optical conductivity of UPd₂Al₃ thin films in the frequency range from 45 MHz to 20 GHz at temperatures from 1.65 K to 300 K. We present spectra revealing the emergence of a strong Drude-like conductivity roll-off at frequencies of only a few GHz as the temperature is decreased (in agreement with the increase of dc conductivity) and discuss the microwave conductivity of UPd₂Al₃ in the framework of the optical properties determined by previous experiments.
[1] M. Dressel et al., Phys. Rev. Lett. 88, 186404 (2002)