Coherent potential approximation

About: Coherent potential approximation is a research topic. Over the lifetime, 1930 publications have been published within this topic receiving 36805 citations.

Full counting statistics of conductance for disordered systems

Abstract: Quantum transport is a stochastic process in nature. As a result, the conductance is fully characterized by its average value and fluctuations, i.e., characterized by full counting statistics (FCS). Since disorders are inevitable in nanoelectronic devices, it is important to understand how FCS behaves in disordered systems. The traditional approach dealing with fluctuations or cumulants of conductance uses diagrammatic perturbation expansion of the Green's function within coherent potential approximation (CPA), which is extremely complicated especially for high order cumulants. In this paper, we develop a theoretical formalism based on nonequilibrium Green's function by directly taking the disorder average on the generating function of FCS of conductance within CPA. This is done by mapping the problem into higher dimensions so that the functional dependence of generating a function on the Green's function becomes linear and the diagrammatic perturbation expansion is not needed anymore. Our theory is very simple and allows us to calculate cumulants of conductance at any desired order efficiently. As an application of our theory, we calculate the cumulants of conductance up to fifth order for disordered systems in the presence of Anderson and binary disorders. Our numerical results of cumulants of conductance show remarkable agreement with that obtained by the brute force calculation.

Electrical transport properties of bulk tetragonal CuMnAs.

Abstract: Temperature-dependent resistivity and magnetoresistance are measured in bulk tetragonal phase of antiferromagnetic CuMnAs and the latter is found to be anisotropic both due to structure and magnetic order. We compare these findings to model calculations with chemical disorder and finite-temperature phenomena included. The finite-temperature ab initio calculations are based on the alloy analogy model implemented within the coherent potential approximation and the results are in fair agreement with experimental data. Regarding the anisotropic magnetoresistance (AMR) which reaches a modest magnitude of 0.12%, we phenomenologically employ the Stoner-Wohlfarth model to identify temperature-dependent magnetic anisotropy of our samples and conclude that the field-dependence of AMR is more similar to that of antiferromagnets than ferromagnets, suggesting that the origin of AMR is not related to isolated Mn magnetic moments.

Van Hove Singularity and Superconductivity in Disordered Hubbard Model

Abstract: We apply the Coherent Potential Approximation (CPA) to a simple extended Hubbard model with a nearest and next nearest neighbour hopping for disordered superconductors with s-, d- and p-wave pairing. We show how the Van Hove singularities in the electron density of states enhance the transition temperature Tc for exotic superconductors in a clean and weakly disordered system. The Anderson theorem and pair-breaking effects in presence of Van Hove singularity caused by non-magnetic disorder are also discussed.