## Abstract

To distinguish a metal from an insulator, the Drude weight (D, zero-frequency component of conductivity) is a useful measure, as Kohn pointed out long ago: D>0(=0) for a metal (insulator). Later, Millis and Coppersmith showed that a variational wave function Ψ _{Q} in which the key ingredient for a Mott transition (a doublon-holon binding effect) is introduced exhibits D> 0 (metallic) even for sufficiently large correlation strength, namely, a Mott transition is absent from Ψ _{Q}. In contrast, variational Monte Carlo studies using Ψ _{Q} confirmed, by studying relevant quantities such as doublon density d and a superconducting correlation function P_{d}^{∞}, that Ψ _{Q} undoubtedly raises a Mott transition. This contradiction has been a long-standing perplexing problem. We definitely settle this problem by adding to Ψ _{Q} a configuration-dependent phase factor P_{θ}, which has been hitherto overlooked. This factor appropriately picks out a negative counterpart in D for insulators, so that vanishes. Because P_{θ} does not affect the quantities such as d and P_{d}^{∞}, the previous results of Ψ _{Q} on the Mott transition remain intact for P_{θ} Ψ _{Q}.

Original language | English |
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Pages (from-to) | 5-8 |

Number of pages | 4 |

Journal | Physics Procedia |

Volume | 45 |

DOIs | |

Publication status | Published - 2013 |

Event | 25th International Symposium on Superconductivity, ISS 2012 - Tokyo, Japan Duration: 2012 Dec 3 → 2012 Dec 5 |

## Keywords

- Drude weight
- Hubbard model
- Variational Monte Carlo

## ASJC Scopus subject areas

- Physics and Astronomy(all)