We have measured crystalline electric field (CEF) excitations of Nd3+ ions in
the two-channel Kondo lattice candidates NdT2Zn20 (T = Co, Rh, and Ir) by means
of inelastic neutron scattering (INS). In the INS measurements at 5 K,
dispersionless excitations were observed at 3.8 and 7.2 meV for T = Co, 3.1 and
5.8 meV for T = Rh, and 3.0 and 5.3 meV for T = Ir. Analyses of the temperature
dependence of the INS spectra confirm that the CEF ground states are the Gamma
6 doublet, that is a requisite for manifestation of the magnetic two-channel
Kondo effect. For T = Co, a shoulder was observed at 7.7 meV close to the CEF
excitation peak centered at 7.2 meV. The shoulder is attributed to a bound
state of the CEF and low-lying optical phonon excitations.Comment: 6 pages, 3 figure