Quantum and thermal ionic motion, oxygen isotope effect, and superexchange distribution in La$_2$CuO$_4$
| Autor: | Häfliger, P. S., Gerber, S., Pramod, R., Schnells, V. I., Piazza, B. dalla, Chati, R., Pomjakushin, V., Conder, K., Pomjakushina, E., Dreau, L. Le, Christensen, N. B., Syljuåsen, O. F., Normand, B., Rønnow, H. M. |
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| Rok vydání: | 2013 |
| Předmět: | |
| Zdroj: | Physical Review B 89, 085113 (2014) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1103/PhysRevB.89.085113 |
| Popis: | We study the zero-point and thermal ionic motion in La$_2$CuO$_4$ by means of high-resolution neutron diffraction experiments. Our results demonstrate anisotropic motion of O and to a lesser extent of Cu ions, both consistent with the structure of coupled CuO$_6$ octahedra, and quantify the relative effects of zero-point and thermal contributions to ionic motion. By substitution of $^{18}$O, we find that the oxygen isotope effect on the lattice dimensions is small and negative ($-0.01\%$), while the isotope effect on the ionic displacement parameters is significant ($-6$ to $50\%$). We use our results as input for theoretical estimates of the distribution of magnetic interaction parameters, $J$, in an effective one-band model for the cuprate plane. We find that ionic motion causes only small ($1\%$) effects on the average value $\langle J\rangle$, which vary with temperature and O isotope, but results in dramatic ($10$-$20\%$) fluctuations in $J$ values that are subject to significant ($8$-$12\%$) isotope effects. We demonstrate that this motional broadening of $J$ can have substantial effects on certain electronic and magnetic properties in cuprates. Comment: 13 pages, 9 figures |
| Databáze: | arXiv |
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