Investigation of crystal field excitations of 1D heavy-fermion compounds YbFe5P3 and Yb2Fe12P7

A growing number of quantum material, whose collective quantum mechanical properties give rise to exotic quantum states, have well-defined fractional sets of quasi-particles; for instance, a “spinon” is a quasi-particle that carries spin-1/2, but no charge. There is great interest in understanding the nature of the ground state and low-energy excitations of quantum materials that possess fractional quantum statistics. Recently, some of us investigated Yb based quasi-1D materials YbFe5P3 and Yb2Fe12P7, which exhibit interesting properties. In both cases, the heat capacity shows a clear heavy-fermion behaviour. Further, YbFe5P3 does not order magnetically down to 0.08 K, while Yb2Fe12P7 shows magnetic ordering at 1 K. Therefore, the determination of the true nature of the ground state of these 1D quantum magnets by measuring the crystal field excitations (CEF) is particularly important. We, therefore, propose here to investigate CEF energy level schemes and their wave functions using inelastic neutron scattering study on the MERLIN spectrometer of these two materials.