Regensburg 2022 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 8: Frustrated Magnets – Strong Spin-Orbit Coupling

TT 8.2: Talk

Monday, September 5, 2022, 17:30–17:45, H10

Fractional Excitation-induced Phonon Renormalization in α-RuCl₃ — Adrian Merritt¹, Xiao Wang¹, Alexei Bosak², Luigi Paolasini², Alexandre Ivanov³, Rolf Heid⁴, and •Yixi Su¹ — ¹Jülich Centre for Neutron Science JCNS-FRM II, Forschungszentrum Jülich GmbH, Garching, Germany — ²European Synchrotron Radiation Facility (ESRF), Grenoble, France — ³Institut Laue-Langevin, Grenoble, France — ⁴Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, Karlsruhe, Germany

The quantum spin liquid (QSL) phase is of immense interest to condensed matter physicists, and have been studied for decades. With a Kitaev model that is exactly solvable and gives a QSL ground state, more recent work has focused on the J_eff=1/2 materials and in particular, α-RuCl₃. Above the critical magnetic field B_c 7T and below T 6K there is evidence for the half-integer quantized plateau possibly arising from the fractional excitations in the QSL phase. Recent theoretical work has shown that the fractional excitations can induce phonon renormalization via the spin-lattice coupling, and would in particular affect the acoustic phonons near the zone boundary. Our measurements have focused on the phonon dispersion in α-RuCl₃ to observe this phonon renormalization effect in the putative QSL phase. We have been able to survey the acoustic phonons in the relevant scattering directions under magnetic fields using single crystals. We will discuss our results with a focus on examining the low-energy acoustic phonon branches we measured in comparison to published work as well as the observed phonon renormalization effect.