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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. Adrian211. 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 TN = 14 K and Tc = 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)

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