Abstract for an Invited Paper for the MAR07 Meeting of The American Physical Society Anti-Jahn-Teller effect and d-wave phonon mechanism in cuprates

for an Invited Paper for the MAR07 Meeting of The American Physical Society Anti-Jahn-Teller effect and d-wave phonon mechanism in cuprates HIROSHI KAMIMURA, Tokyo University of Science Undoped cuprates are Jahn-Teller (JT) Materials [1] and Mott AF insulators [2]. When holes are doped, the octahedrons or pyramids elongated by the JT effect shrink. We call such distortion against the JT effect “anti-Jahn-Teller effect”[3]. By the interplay of the anti-Jahn-Teller effect and Mott physics, the two multiplets, the Zhang-Rice singlet and the Hund’s coupling triplet, become nearly degenerate, and thus the hole-carriers in the underdoped regime form a metallic state, by taking the two multiplets alternately in the presence of the local AF order without destroying it [3,4]. On the basis of this two-component K-S model with small Fermi surfaces, the mechanism of superconductivity is discussed by the interplay of the electron-phonon interactions and local AF order [5,3]. It is shown that (1) the phase difference of wave functions between upand down-spin carriers leads to the gap of dx2-y2 symmetry, and (2) the calculated concentration dependences of Tc and of isotope effects for LSCO are consistent with recent experimental results including anomalous isotope effects [6]. Finally the origin of the high-energy pseudogap is discussed based on the K-S model [3]. [1] J.G. Bednorz and K.A. Mueller, Z. Phys. B64, 189 (1986). [2] P.W. Anderson, Science 235, 1196 (1987). [3] H. Kamimura et al., in Theory of Copper Oxide Superconductors (Springer, Heidelberg, 2005). [4] H. Kamimura and Y. Suwa, J. Phys. Soc. Jpn. 62, 3368 (1993). [5] H. Kamimura et al. Phys. Rev. Lett. 77, 723 (1996). [6] A.R. Bishop et al., J. Supercond., to be published (2006).