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Pressure-induced phase transition and bi-polaronic sliding in a hole-doped Cu_2O_3 ladder system

E. Kaneshita·I. Martin·A. R. Bishop
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Abstract

We study a hole-doped two-leg ladder system including metal ions, oxygen, and electron-lattice interaction, as a model for Sr_{14-x}Ca_xCu_{24}O_{41-δ}. Single- and bi-polaronic states at 1/4-hole doping are modeled as functions of pressure by applying an unrestricted Hartree-Fock approximation to a multiband Peierls-Hubbard Hamiltonian. We find evidence for a pressure-induced phase transition between single-polaron and bi-polaron states. The electronic and phononic excitations in those states, including distinctive local lattice vibrational modes, are calculated by means of a direct-space Random Phase approximation. Finally, as a function of pressure, we identify a transition between site- and bond-centered bi-polarons, accompanied by a soft mode and a low-energy charge-sliding mode. We suggest comparisons with available experimented data.

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E. Kaneshita, I. Martin, A. R. Bishop. 2006-04-06. Pressure-induced phase transition and bi-polaronic sliding in a hole-doped Cu_2O_3 ladder system. https://doi.org/10.1103/physrevb.73.094514

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