Tunneling and rattling in clathrate crystal

Abstract

We present tunneling and rattling motions of an off-center guest atom in cage referring to a clathrate crystal La_3Pd_{20}Ge_6. The elastic constant C_{44} of La_3Pd_{20}Ge_6 shows a Debye-type dispersion around 20 K obeying a relaxation time tau = tau_0exp(E/k_{B}T) with an attempt time tau_0 = 2.0*10^{-12} sec and an activation energy E = 197 K. At low temperatures below 3 K down to 20 mK, the C_{44} shows a softening of C_{44} = C_{44}^0(T-T_C^0)/(T-Theta) with T_C^0 = -337.970 mK and Theta = -338.044 mK. These facts are attributed to two different types of the off-center motions with Gamma_5 symmetry in 4a-site cage of La_3Pd_{20}Ge_6, a thermally activated rattling motion over the potential hill and a tunneling motion through the potential hill at low temperatures.

arXiv comment5 pages, 4 figures, to be published Phys. Rev. B

References in corpus (4)

• Quadrupolar effect and rattling motion in heavy fermion superconductor PrOs_4Sb_{12}
• Ferroquadrupole ordering and Gamma_5 rattling motion in clathrate compound Ce_3Pd_20Ge_6
• Four-well tunneling states and elastic response of clathrates
• Two-Channel Kondo Model as a Fixed Point of Local Electron-Phonon Coupling System

Cited by in corpus (10)

• Local Heavy Quasiparticle in Four-Level Kondo Model
• Evidence for the Single-Site Quadrupolar Kondo Effect in the Dilute non-Kramers System Y${}_{1-x}$Pr${}_x$Ir${}_2$Zn${}_{20}$
• Stability frontiers in the AM${}_6$X${}_6$ kagome metals: The LnNb${}_6$Sn${}_6$ (Ln:Ce-Lu,Y) family and density-wave transition in LuNb${}_6$Sn${}_6$
• Theory of Ultrasonic Dispersion in Local Phonon Systems Coupled with Conduction Electrons
• Magnetic-Field-Independent Ultrasonic Dispersions in the Magnetically Robust Heavy Fermion System SmOs4Sb12
• Quadrupolar Susceptibility and Magnetic Phase Diagram of PrNi${}_2$Cd${}_{20}$ with Non-Kramers Doublet Ground State
• Green's function of fully anharmonic lattice vibration
• Elastic Response in the Dilute non-Kramers System Y${}_{1-x}$Pr${}_x$Ir${}_2$Zn${}_{20}$
• Synthesis and characterization of the novel breathing pyrochlore compound Ba3Tm2Zn5O11
• Elastic Softening in Synthetic Diamonds