Related papers: Electromagnetic response of superconductors and op…
The restricted optical sum rule and its dependence on the temperature, a superconducting gap and the cutoff energy have been investigated. As known this sum rule depends on the cutoff energy and the relaxation rate even for a homogeneous…
The theory that the change of the electronic kinetic energy in a direction perpendicular to the CuO-planes in high-temperature superconductors is a substantial fraction of the condensation energy is examined. It is argued that the…
Much attention has been given to a possible violation of the optical sum rule in the cuprates, and the connection this might have to kinetic energy lowering. The optical integral is composed of a cut-off independent term (whose temperature…
We examine the temperature dependence of the optical sum rule in the normal state due to interactions. To be concrete we adopt a weak coupling approach which uses an electron-boson exchange model to describe inelastic scattering of the…
We theoretically analyze some of the anomalies of the optical sumrules in the high-temperature superconductors. In particular we address the particularly strong dependence on temperature of the sumrule in the normal state. Both…
We derive the restricted optical-conductivity sum rule for a model with circulating orbital currents. It is shown that an unusual coupling of the vector potential to the interaction term of the model Hamiltonian results in a non-standard…
For a system with a fixed number of electrons, the total optical sum is a constant, independent of many-body interactions, of impurity scattering and of temperature. For a single band in a metal, such a sum rule is no longer independent of…
The f-sum rule is introduced and its applications to electronic and vibrational modes are discussed. A related integral over the intra-band part of sigma(omega) which is also valid for correlated electrons, becomes just the kinetic energy…
We begin with an overview of the experimental results for the temperature and doping dependences of the optical-conductivity spectral weight in cuprate superconductors across the whole phase diagram. Then we discuss recent attempts to…
The mechanism of high-Tc superconductivity is investigated with interests on the microscopic aspects of the condensation energy. The theoretical analysis is performed on the basis of the FLEX approximation which is a microscopic description…
We discuss the problem of a possible "violation" of the optical sum rule in the normal (non superconducting) state of strongly correlated electronic systems, using our recently proposed DMFT+Sigma approach, applied to two typical models:…
A sum rule for the first frequency moment of the optical absorption of a many-polaron system is derived, taking into account many-body effects in the system of constituent charge carriers of the many-polaron system. In our expression for…
In the conventional BCS description of a superconductor the kinetic energy increases in the superconducting state. We describe the observed decrease in kinetic energy by adopting a simple model of electrons whose elastic scattering rate…
A single band optical sum rule derived by Kubo can reveal a novel kind of superconducting state. It relies, however, on a knowledge of the single band contribution from zero to infinite frequency. A number of experiments over the past five…
An important quantity in electronic systems is the quasiparticle scattering rate (QPSR). A related optical scattering rate (OSR) is routinely extracted from optical data, and, while it is not the same as the QPSR, it nevertheless displays…
Various sum rules accounting for the coupling between density and particle excitations and emphasizing in an explicit way the role of the Bose-Einstein condensation are discussed. Important consequences on the fluctuations of the particle…
The model of hole superconductivity predicts that the superfluid weight in the zero-frequency $\delta$-function in the optical conductivity has an anomalous contribution from high frequencies, due to lowering of the system's kinetic energy…
We provide a brief summary of the observed sum rule anomalies in the high-T$_c$ cuprate materials. A recent issue has been the impact of a non-infinite frequency cutoff in the experiment. In the normal state, the observed anomalously high…
The condensation energy can be shown to be a moment of the change in the occupied part of the spectral function when going from the normal to the superconducting state. As a consequence, there is a one to one correspondence between the…
Partial sum rules are widely used in physics to separate low- and high-energy degrees of freedom of complex dynamical systems. Their application, though, is challenged in practice by the always finite spectrometer bandwidth and is often…