Optical Conductivity of the Trellis-Lattice t-J Model: Charge Fluctuations in NaV_2O_5

抄録

Optical conductivity of the trellis lattice t-J model at quarter filling is calculated by an exact-diagonalization technique on small clusters, whereby the valence state of V ions of NaV₂O₅ is considered. We show that the experimental features at --1 eV, including peak positions, presence of shoulders, and anisotropic spectral weight, can be reproduced in a reasonable range of parameter values, only by assuming that the system is in the charge disproportionated ground state. Possible reconciliation with experimental data suggesting the presence of uniform ladders at T>T_c is discussed.