Breakdown of Hooke's law of elasticity at the Mott critical endpoint in an organic conductor.

The Mott metal-insulator transition, a paradigm of strong electron-electron correlations, has been considered as a source of intriguing phenomena. Despite its importance for a wide range of materials, fundamental aspects of the transition, such as its universal properties, are still under debate. We report detailed measurements of relative length changes Δ/ as a function of continuously controlled helium-gas pressure for the organic conductor κ-(BEDT-TTF)Cu[N(CN)]Cl across the pressure-induced Mott transition.

Probing the Mott physics in κ-(BEDT-TTF)₂X salts via thermal expansion.

In the field of interacting electron systems the Mott metal-to-insulator (MI) transition represents one of the pivotal issues. The role played by lattice degrees of freedom for the Mott MI transition and the Mott criticality in a variety of materials are current topics under debate. In this context, molecular conductors of the κ-(BEDT-TTF)2X type constitute a class of materials for unraveling several aspects of the Mott physics.

Mott metal-insulator transition on compressible lattices.

The critical properties of the finite temperature Mott end point are drastically altered by a coupling to crystal elasticity, i.e., whenever it is amenable to pressure tuning.

Scaling theory of the mott transition and breakdown of the Grüneisen scaling near a finite-temperature critical end point.

We discuss a scaling theory of the lattice response in the vicinity of a finite-temperature critical end point. The thermal expansivity is shown to be more singular than the specific heat such that the Grüneisen ratio diverges as the critical point is approached, except for its immediate vicinity. More generally, we express the thermal expansivity in terms of a scaling function which we explicitly evaluate for the two-dimensional Ising universality class.

A functional renormalization group approach to the Anderson impurity model.

We develop a functional renormalization group approach which describes the low-energy single-particle properties of the Anderson impurity model up to intermediate on-site interactions [Formula: see text], where Δ is the hybridization in the wide-band limit. Our method is based on a generalization of a method proposed by Schütz et al (2005 Phys. Rev.

Absence of fermionic quasiparticles in the superfluid state of the attractive fermi gas.

We calculate the effect of order parameter fluctuations on the fermionic single-particle excitations in the superfluid state of neutral fermions interacting with short-range attractive forces. We show that in dimensions D< or =3 the singular effective interaction between the fermions mediated by the gapless Bogoliubov-Anderson mode prohibits the existence of well-defined quasiparticles. We explicitly calculate the single-particle spectral function in the BEC regime in D=3 and show that in this case the quasiparticle residue and the density of states are logarithmically suppressed.

Non-fermi-liquid behavior of quasi-one-dimensional pseudogap materials.

We study the spectral function of the pseudogap phase of quasi-one-dimensional charge density wave materials. Using a stochastic approach and emphasizing an exact treatment of non-Gaussian order parameter fluctuations we will go beyond a usual perturbative calculation. Our results give a good fit to angle-resolved photoemission spectroscopy data and explain the absence of the Fermi edge in charge density wave materials even above the Peierls transition, indicating non-Fermi-liquid behavior.