Quantum Critical Fluctuation in Heavy Fermion Compound Ce(Ni0.935Ni0.065)2Ge2

Cuihuan Wang (Oak Ridge National Laboratory)

A number of experiments have been done on heavy fermion compounds to study quantum critical behavior. The results for both the bulk properties and for the neutron scattering spectra can be explained either in the framework of traditional spin fluctuation theory or via local critical E/T scaling[1]. On approaching the quantum critical point (QCP), the correlation time t diverges more rapidly than the correlation length x with t proportional to xz [2]. In traditional spin fluctuation theory, a central assumption is that z=2 for a three dimensional (3D) itinerant antiferromagnet (AF) near the QCP. We use inelastic neutron scattering to measure the correlation time and correlation length in the heavy fermion compound Ce(Ni0.935Ni0.065)2Ge2, which is believed to sit in the vicinity of a QCP. Our results show that the temperature dependent inverse correlation time and inverse staggered susceptibility follow T3/2 behavior. Taken together with the reported bulk properties, this means that Ce(Ni0.935Ni0.065)2Ge2 can be characterized in the framework of traditional spin fluctuation theory for a 3D itinerant AF near a QCP. Our most important result about this compound is that t versus x varies as t= a + b xz with z=2. Hence we experimentally demonstrate a central assumption of the traditional spin fluctuation theory.

[1] Q. Si, S. Rabello, K. Ingersent and J. Llewellun Smith, Nature 413, 804 (2001); G. R. Stewart, Rev. Mod. Phys. 73, 797 (2001). [2] J. A. Hertz , Phys. Rev. B 14, 1165 (1976); Millis A J, Phys. Rev. B 48, 7183 (1993); T. Moriya and T. Takimoto, J. Phys. Soc. Jpn. 64, 960 (1995).

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