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Lattice vibrations of alpha'-NaV_2O_5 in the low-temperature phase. Magnetic bound states?

M. N. Popova·A. B. Sushkov·S. A. Klimin·E. P. Chukalina·B. Z. Malkin·M. Isobe·Yu. Ueda
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Abstract

We report high resolution polarized infrared studies of the quarter-filled spin ladder compound alpha'-NaV_2O_5 as a function of temperature (5K <= T <= 300K). Numerous new modes were detected below the temperature T_c=34K of the phase transition into a charge ordered nonmagnetic state accompanied by a lattice dimerization. We analyse the Brillouin zone (BZ) folding due to lattice dimerization at T_c and show that some peculiarities of the low-temperature vibrational spectrum come from quadruplets folded from the BZ point (1/2, 1/2, 1/4). We discuss an earlier interpretation of the 70, 107, and 133cm-1 modes as magnetic bound states and propose the alternative interpretation as folded phonon modes strongly interacting with charge and spin excitations.

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M. N. Popova, A. B. Sushkov, S. A. Klimin, E. P. Chukalina, B. Z. Malkin, M. Isobe, Yu. Ueda. 2001-07-14. Lattice vibrations of alpha'-NaV_2O_5 in the low-temperature phase. Magnetic bound states?. https://doi.org/10.1103/physrevb.65.144303

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