@article{oai:niigata-u.repo.nii.ac.jp:00002030,
 author = {Yamakawa, Y. and Mitsumoto, K. and Ono, Y.},
 issue = {2},
 journal = {Journal of Magnetism and Magnetic Materials, Journal of Magnetism and Magnetic Materials},
 month = {Mar},
 note = {Recently, Goto et al. have discovered anomalous elastic softening due to vacancy in crystalline silicon at very low temperature. To investigate the quantum state of the silicon vacancy, we introduce a cluster model which includes the electron-lattice coupling between electrons and Jahn-Teller distortions together with the Coulomb interaction between electrons. By using the numerical diagonalization method, we take into account of both the nonadiabatic and the correlation e ects. We  nd that the 3-fold orbital degeneracy in the ground state of a silicon vacancy is stable against the Jahn-Teller distortions because of the strong quantum fluctuation due to the nonadiabatic coupling between electrons and Jahn-Teller distortions. The obtained result is a striking contrast to the previous theoretical results within the adiabatic approximation and is consistent with the newly observed experiment.},
 pages = {993--995},
 title = {Nonadiabatic Interaction between Electrons and Jahn-Teller Distortions in a Silicon Vacancy},
 volume = {310},
 year = {2007}
}