## Abstract

We present an exact-diagonalization study of the frequency- and wave-vector-dependent conductivity sigma(q,omega) in small clusters in the two-dimensional t-J model. Unlike the related dynamical density correlation function, sigma(q=0,omega) in the underdoped regime has the exchange constant J as its characteristic energy scale and is dominated by a resonancelike excitation with frequency similar to 1.7 J. We interpret this as transition to a p-like excited state of a spin-bag-type quasiparticle (or, alternatively, a tightly bound spinon-holon pair) and show that a simple calculation based on the string picture explains the numerical results semiquantitatively. For doping levels greater than or equal to 25% t remains the only energy scale of sigma(q=0,omega).

Original language | English |
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Pages (from-to) | 11034 - 11037 |

Number of pages | 4 |

Journal | Physical Review B |

Volume | 54 |

Issue number | 16 |

DOIs | |

Publication status | Published - 15-Oct-1996 |

## Keywords

- T-J MODEL
- SPIN
- DYNAMICS
- HUBBARD
- CHARGE