Destabilization criteria of the in-plane Cu $c$-axis dynamics in cuprate superconductors

N. Kristoffel; M. Klopov

doi:doi:10.1209/epl/i2001-00110-7

DOI: 10.1209/epl/i2001-00110-7

Europhys. Lett., 55 (5) , pp. 686-690 (2001)

Destabilization criteria of the in-plane Cu c-axis dynamics in cuprate superconductors

N. Kristoffel¹ and M. Klopov²

¹ Institute of Physics, University of Tartu - Riia 142, 51014 Tartu, Estonia
² Tallinn Technical University - Ehitajate tee 5, 19086 Tallinn, Estonia

kolja@fi.tartu.ee

(Received 20 February 2001; accepted in final form 13 June 2001)

Abstract
Destabilization criteria of the in-plane Cu c-axis local dynamics in tetragonal La₂CuO₄ (also YBaCuO) have been found using the Green's function method. The build-up of the soft low-frequency resonances has been traced. Relatively small force constants weakenings can lead to Cu out-of-plane distortions. For the Y-system the criterion is stronger, the a-axis destabilization asks for smaller perturbations as compared with the c-axis one. The criteria found are expected to work in various realizations by doping-induced charge redistributions leading to local displacement distortion responses.