Nonlinear transport of electrons in strong electric fields, as typified by dielectric breakdown,
is reformulated in terms of the ground-state decay rate originally studied by Schwinger in …

Inspired by the observation of a robust d-wave superconducting phase driven by tuning the
next-nearest-neighbor (NNN) electron hop** in recent density matrix renormalization …

We propose an order parameter to characterize valence-bond-solid (VBS) states in quantum
spin chains, given by the ground-state expectation value of a unitary operator appearing in …

We elucidate the mechanism for instability of topological Thouless pum** in strongly
interacting systems from a viewpoint of symmetry-protected topological phases. If the …

We discuss the characterization of the polarization for insulators under the periodic
boundary condition in terms of the Berry phase, clarifying confusing subtleties. For band …

We present a generalization of the recently proposed variational cluster perturbation theory
to extended Hubbard models at half-filling with repulsive nearest neighbor interaction. The …

The quantized Hall conductivity of integer and fractional quantum Hall (IQH and FQH) states
is directly related to a topological invariant, the many-body Chern number. The conventional …

We discuss quantum Hall effects in a gapped insulator on a periodic two-dimensional lattice.
We derive a universal relation among the quantized Hall conductivity, and charge and flux …

We revisit the ground-state phase diagram of the one-dimensional half-filled extended
Hubbard model with on-site (U) and nearest-neighbor (V) repulsive interactions. In the first …

We investigate magnetic quantum phases and the topological quantum phase transition
between two distinct valence-bond solid (VBS) phases of a minimal interacting spin-chain …