The idea of exciton condensation in solids was introduced in the 1960s with the analogy of
superconductivity in mind. While exciton supercurrents have been realised only in artificial …

Perturbation series expansion methods are sophisticated numerical tools used to provide
quantitative calculations in many areas of theoretical physics. This book gives a …

This article represents a continuation of a paper on AnBnO3n+ 2= ABOx compounds which
was published in 2001 in this journal. This work reports also on oxides of the type A′ Ak …

The excitonic insulator is an electronically driven phase of matter that emerges upon the
spontaneous formation and Bose condensation of excitons. Detecting this exotic order in …

The fundamental idea of the excitonic insulator (EI) driven by electron–hole correlations in
narrow-gap semiconductors or semimetals was originally proposed in the 1960s, and only …

Electric deflections of gas-phase, cryogenically cooled, neutral niobium clusters [Nb N;
number of atoms (N)= 2 to 150, temperature (T)= 20to 300kelvin], measured in molecular …

We act on the suggestion that an excitonic insulator state might separate—at very low
temperatures—a semimetal from a semiconductor and ask for the nature of these transitions …

We study the spontaneous symmetry breaking of the excitonic insulator state induced by the
Coulomb interaction U in the two-dimensional extended Falicov-Kimball model. Using the …

We explore the spontaneous formation of an excitonic insulator state at the semimetal-
semiconductor transition of mixed-valence materials in the framework of the spinless Falicov …

The variational cluster approximation is used to study the spontaneous symmetry breaking
of the excitonic insulator (EI) state in the two-orbital Hubbard model defined on the two …