Fermi surface nesting in disordered Cu1-xPdx alloys

Extreme Fermi Surface Smearing in a Maximally Disordered Concentrated Solid Solution

We show that the Fermi surface can survive the presence of extreme compositional disorder in the equiatomic alloy Ni_{0.25}Fe_{0.25}Co_{0.25}Cr_{0.25}. Our high-resolution Compton scattering experiments reveal a Fermi surface which is smeared across a significant fraction of the Brillouin zone (up to 40% of 2π/a). The extent of this smearing and its variation on and between different sheets of the Fermi surface have been determined, and estimates of the electron mean free path and residual resistivity have been made by connecting this smearing with the coherence length of the quasiparticle states.

Special directions in momentum space. II. Hexagonal, tetragonal and trigonal symmetries

This paper is a continuation of a previous one,Special directions in momentum space. I. Cubic symmetries[Kontrym-Sznajd & Samsel-Czekała (2011).J. Appl. Cryst.44, 1246–1254], where new sets of special directions (SDs), having the full symmetry of the Brillouin zone, were proposed for cubic lattices. In the present paper, such directions are derived for structures with unique six-, four- and threefold axes,i.e.hexagonal, tetragonal and trigonal lattices, for both two- and three-dimensional space. The SDs presented here allow for construction, in the whole space, of anisotropic quantities from the knowledge of such quantities along a limited number of SDs. The task at hand is to determine as many anisotropic components as the number of available sampling directions. Also discussed is a way of dealing with data when the number of anisotropic components is restricted by a non-optimal set of SDs.

Direct observation of the multisheet Fermi surface in the strongly correlated transition metal compound ZrZn2

The existence of flat areas of a Fermi surface (FS), predicted by electronic structure calculations and used in models of both magnetically mediated and phonon-mediated Fulde-Ferrell-Larkin-Ovchinnikov superconducting states, is reported in the paramagnetic phase of the ferromagnetic superconductor ZrZn2 using positron annihilation. The strongly mass-renormalized FS sheet, dominating the Fermi level density of states, is seen for the first time. The delocalization of the magnetization is studied using measured and calculated magnetic Compton profiles.

Charge distributions in metallic alloys: a charge-excess functional theory approach

The distribution of local charge (DLC) excesses in metallic alloys, previously obtained as a result of the analysis of order N electronic structure calculations, is derived from a variational principle. A phenomenological charge-excess functional theory is obtained which is determined by three concentration dependent, material specific parameters that can be obtained from ab initio calculations. The theory requires modest computational efforts and reproduces with an excellent accuracy the DLC and the electrostatic energies of ordered, substitutionally disordered, or segregating metallic alloys and, hence, can be considered an efficient approach alternative to conventional electronic structure calculations. The substantial reduction of computing time opens new perspectives for the understanding of metallic systems and their mechanical properties.

Mobility spectrum computational analysis using a maximum entropy approach

A method to calculate a smooth electrical conductivity versus mobility plot ("mobility spectrum") from the classical magnetoconductivity tensor in heterogeneous structures with the help of a "maximum entropy principle" has been developed. In this approach the closeness of the fit and the entropy of the mobility spectrum are optimized. The spectrum is then the most probable one with the least influence of the personal bias of the investigator for any given set of experimental data and is maximally noncommittal with regard to the unmeasured data. The advantages of the maximum entropy mobility spectrum analysis as compared to the conventional mobility spectrum analysis are demonstrated using a synthetic dataset.