Quadrupole fluctuation and off-center rattling motion in heavy fermion superconductor PrOs4Sb12

✍ Scribed by Terutaka Goto; Yuichi Nemoto; Kazuhiro Sakai; Kei Onuki; Takashi Yamaguchi; Mitsuhiro Akatsu; Tatsuya Yanagisawa; Hitoshi Sugawara; Hideyuki Sato

• Publisher: Elsevier Science
• Year: 2005
• Tongue: English
• Weight: 369 KB
• Volume: 359-361
• Category: Article
• ISSN: 0921-4526
• DOI: 10.1016/j.physb.2005.01.241

✦ Synopsis

We have made ultrasonic measurements on a filled skutterudite PrOs 4 Sb 12 showing a heavy Fermion superconductivity at T C ¼ 1:85 K: The elastic constants ðC 11 À C 12 Þ=2 and C 44 of PrOs 4 Sb 12 exhibit low-temperature softenings below 20 K down to T C ; indicating a quadrupole fluctuation of Pr 3þ ion. A minimum of ðC 11 À C 12 Þ=2 in magnetic fields along the [1 1 0] direction around 8 T shows a level crossing of one of a excited G ð2Þ 4 triplet to a ground state G 1 singlet. An ultrasonic dispersion in ðC 11 À C 12 Þ=2 around 30 K suggests a thermally activated off-center rattling of Pr ion in a cage of Sb-icosahedron. The observed relaxation time shows the Arrhenius-type temperature dependence t ¼ t 0 expðE=k B TÞ with an attempt time t 0 ¼ 8:8 Â 10 À11 s and an activation energy E ¼ 168 K: The charge fluctuation of the off-center motion and the quadrupole fluctuation of the 4f electron may participate in the formation of the heavy fermion and the superconductivity in PrOs 4 Sb 12 .