High-field spin dynamics in Kitaev quantum spin liquid candidate α-RuCl3

We study the evolution of the high and low-energy magnetic excitations across the 7 T through 12 T regime in paradigmatic Kitaev spin liquid candidate a-RuCl3. Interestingly, the excitations behave differently depending on field directions H||armchair vs. zig-zag. We reveal distinct sharp spin wave patterns above 12 T which, on reducing the field to 8 T, transform into delocalized broad excitations for the field along zig-zag. However, sharp modes remain for the field along the armchair axis. Moreover, focusing on the low-energy part of the spectrum yields new insights into the nature of the spin gap.