Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 38: f-Electron Systems and Heavy Fermions

TT 38.5: Vortrag

Mittwoch, 3. April 2019, 10:45–11:00, H23

Switching the propagation vector of the hidden-order phase in Ce₃Pd₂₀Si₆ with a magnetic field — •Pavlo Y. Portnichenko¹, Stanislav E. Nikitin², Andrey Prokofiev³, Silke Paschen³, Jean-Michel Mignot⁴, Jacques Ollivier⁵, Andrey Podlesnyak⁶, Siqin Meng^7,8, Zhilun Lu⁸, and Dmytro S. Inosov¹ — ¹IFMP, TU Dresden, Germany — ²MPI-CPfS, Dresden, Germany — ³Vienna Univ. of Technology, Austria — ⁴LLB, France — ⁵ILL, France — ⁶SNS, Oak Ridge, USA — ⁷CIAE, Beijing, China — ⁸HZB, Berlin, Germany

Hidden-order phases that occur in a number of correlated f-electron systems are among the most elusive states of electronic matter. The heavy-fermion compound Ce₃Pd₂₀Si₆ exhibits magnetically hidden order that occurs at subkelvin temperatures, known as phase II. Additionally, only in a magnetic field applied parallel to the [001] cubic axis, another field-induced phase II^′ was observed in magnetization measurements, yet the nature of the II-II^′ phase transition has remained a mystery. Here we use inelastic neutron scattering to demonstrate that this transition is associated with a switching in the propagation vector of the antiferroquadrupolar order from (111) to (100) with a simultaneous change in the type of the ordered quadrupole from O₂⁰ to O_xy. Despite the absence of magnetic Bragg scattering in the phase II^′, its propagation vector was revealed by the location of an intense soft mode in the excitation spectrum along the (100) direction, orthogonal to the applied field. Our experiment also reveals collective excitations in the field-polarized paramagnetic phase, after phase II^′ is suppressed.