Dresden 2006 – scientific programme

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TT: Tiefe Temperaturen

TT 13: Correlated Electrons: Metal Insulator Transition - Part 1

TT 13.4: Talk

Tuesday, March 28, 2006, 12:30–12:45, HSZ 105

On the nature of the pressure-induced insulator-to-metal transition in LaMnO₃ — •A. Yamasaki, M. Feldbacher, O. K. Andersen, and K. Held — Max-Planck Institut für Festkörperphysik, Stuttgart

Since the discovery of colossal magnetoresistance (CMR), manganites have been intensively studied. In this talk, we focus on the pressure-induced insulator-to-metal (IM) transition which was found experimentally by Loa et al. [1] in the undoped parent compound LaMnO₃ with configuration t_2g³e_g. This transition occurs at room temperature, well above the magnetic ordering ( T_N=140 K) and well below the cooperative Jahn-Teller temperature (T_oo=740K at 0GPa), and at a hydrostatic pressure of 32GPa where the JT distortion appears to be completely suppressed [1]. The IM transition thus seems to be a bandwidth-driven Mott-Hubbard transition of the e_g electrons and points to the dominating importance of the Coulomb repulsion between two e_g electrons on the same site. We employ the local density approximation combined with static and dynamical mean-field theories (LDA+U and LDA+DMFT) and conclude that the insulator-to-metal transition observed at 32GPa in paramagnetic LaMnO₃ at room temperature is not a Mott transition, but is caused by the overlap of the majority-spin e_g bands, orbitally polarized by the Coulomb repulsion.

[1] I. Loa et al., Phys. Rev. Lett. 87, 125501 (2001).