- 著者
- Ryu S. Hatsugai Y.
- 出版者
- American Physical Society
- 雑誌
- Physical review B (ISSN:10980121)
- 巻号頁・発行日
- vol.73, no.24, pp.245115, 2006-06
- 被引用文献数
- 138
The entanglement entropy (von Neumann entropy) has been used to characterize the complexity of many-body ground states in strongly correlated systems. In this paper, we try to establish a connection between the lower bound of the von Neumann entropy and the Berry phase defined for quantum ground states. As an example, a family of translational invariant lattice free fermion systems with two bands separated by a finite gap is investigated. We argue that, for one-dimensional (1D) cases, when the Berry phase (Zak's phase) of the occupied band is equal to pi×(odd integer) and when the ground state respects a discrete unitary particle-hole symmetry (chiral symmetry), the entanglement entropy in the thermodynamic limit is at least larger than ln 2 (per boundary), i.e., the entanglement entropy that corresponds to a maximally entangled pair of two qubits. We also discuss how this lower bound is related to vanishing of the expectation value of a certain nonlocal operator which creates a kink in 1D systems.
- 著者
- Otsuka Y. Hatsugai Y.
- 出版者
- American Physical Society
- 雑誌
- Physical review B (ISSN:01631829)
- 巻号頁・発行日
- vol.65, no.7, pp.073101, 2002-01
- 被引用文献数
- 15
Effects of the electron-electron interaction in the two-dimensional flux phase are investigated. We treat the half-filled Hubbard model with a magnetic flux π per plaquette by the quantum Monte Carlo method. When the interaction is small, an antiferromagnetic long-range order does not exist. It suggests that the Mott transition occurs at finite strength of the interaction in the flux phase, which is in contrast to the standard Hubbard model.
- 著者
- Otsuka Y. Morita Y. Hatsugai Y.
- 出版者
- American Physical Society
- 雑誌
- Physical review B (ISSN:01631829)
- 巻号頁・発行日
- vol.66, no.7, pp.073109, 2002-08
- 被引用文献数
- 7
We investigate anisotropic charge fluctuations in the two-dimensional Hubbard model at half-filling. By the quantum Monte Carlo method, we calculate a momentum-resolved charge compressibility κ(k)=d〈n(k)〉/dμ, which shows the effects of an infinitesimal doping. At the temperature T∼t2/U, κ(k) shows a peak structure at the (±π/2,±π/2) points along the
- 著者
- Taniguchi H. Morita Y. Hatsugai Y.
- 出版者
- American Physical Society
- 雑誌
- Physical review B (ISSN:10980121)
- 巻号頁・発行日
- vol.71, no.13, pp.134417, 2005-04
- 被引用文献数
- 6 5
Based on quantum Monte Carlo calculations, we shall discuss the regime where ferromagnetic correlation isdominant in the two-dimensional t-t8 Hubbard model at a finite temperature. In this model, ferromagnetismcompetes with antiferromagnetism and we reveal how crossover occurs between them at a finite temperature bythe bias-free method. We shall investigate the data in the context of the so-called “low-density ferromagnetism.”The weak-coupling result is also shown and the data are compared with the “Nagaokaferromagnetism.”