Regensburg 2016 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 43: Correlated Electrons: f-Electron & Heavy Fermion Systems

TT 43.3: Vortrag

Mittwoch, 9. März 2016, 10:00–10:15, H20

Magnetic field dependence of spin fluctuations in CeB₆ — •P. Y. Portnichenko¹, A. V. Semeno², H. Ohta³, A. S. Cameron¹, M. A. Surmach¹, H. Jang^4,5, G. Friemel⁴, A. V. Dukhnenko⁶, N. Yu. Shitsevalova⁶, V. B. Filipov⁶, A. Schneidewind⁷, J. Ollivier⁸, A. Podlesnyak⁹, S. V. Demishev², and D. S. Inosov^1,4 — ¹TU Dresden, Germany — ²GPI of RAS, Moscow, Russia — ³Kobe University, Japan — ⁴MPI Stuttgart, Germany — ⁵SLAC, Stanford, USA — ⁶IMPS, Kiev, Ukraine — ⁷JCNS, Jülich, Germany — ⁸ILL, Grenoble, France — ⁹SNS, Oak Ridge, USA

The heavy fermion metal CeB₆ with a simple cubic crystal structure is characterized by a rich magnetic-field – temperature phase diagram. The zero-field antiferromagnetic ground state can be suppressed by an external field of only 1.7 T, above which an antiferroquadrupolar phase II is stabilized, resulting in a field-induced quantum critical point (QCP). Our recent inelastic neutron scattering (INS) studies have revealed a complex spectrum of low-energy collective excitations with intensity maxima at the Γ and R points. We have followed the magnetic field dependence of the excitation spectrum across the QCP. Our data reveal a nonmonotonic behavior of the strong ferromagnon mode at the Γ point, as it initially gets suppressed and becomes quasielastic, but then develops into a collective mode within phase II. At high fields, it follows the same linear behavior as one of the recently discovered electron-spin resonances, proving the common origin of these excitations. An even more complex field dependence was also observed at the R point, where a second low-energy mode emerges in phase II.