Kondo effect emerging from a spin-vibronic state

2014

Self Cite

We discuss the Kondo effect in a spinless two-orbital conduction electron system coupled with anharmonic Jahn-Teller vibration by employing a numerical renormalization group technique. When a temperature T is decreased, we encounter a plateau of log 3 entropy due to quasi-triple degeneracy of local low-energy states, composed of vibronic ground states and the first excited state with an excitation energy of ∆E. Around at T ≈∆E, we observe an entropy change from log 3 to log 2. This log 2 entropy originates from the rotational degree of freedom of the vibronic state and it is eventually released due to the screening by orbital moments of conduction electrons, leading to the Kondo effect of a Jahn-Teller ion. The Kondo temperature is explained by the effective s-d model with anisotropic exchange interactions.

show abstract

Section: Discussion and Summarymentioning

confidence: 99%

Kondo Effect of a Jahn–Teller Ion Vibrating in a Cubic Anharmonic Potential

2014

Self Cite

show abstract

Chaos in Jahn–Teller Rattling

Shudo

2014

Self Cite

We unveil chaotic behavior hidden in the energy spectrum of a Jahn-Teller ion vibrating in a cubic anharmonic potential as a typical model for rattling in cage-structure materials. When we evaluate the nearest-neighbor level-spacing distribution P (s) of eigenenergies of the present oscillator system, we observe the transition of P (s) from the Poisson to the Wigner distribution with the increase of cubic anharmonicity, showing the occurrence of chaos in the anharmonic Jahn-Teller vibration. The energy scale of the chaotic region is specified from the analysis of P (s) and we discuss a possible way to observe chaotic behavior in the experiment of specific heat. It is an intriguing possibility that chaos in nonlinear physics could be detected by a standard experiment in condensed matter physics.

show abstract

Effect of Local Jahn–Teller Phonons on Quantum Critical Point in a Two-Orbital Anderson Model

Matsumoto

2022