arXiv subjects

T. Pruschke

Publications and source records attributed to T. Pruschke.

26 records · Page 2Linked to original sources

arXiv2008

The ALPS project release 1.3: open source software for strongly correlated systems

We present release 1.3 of the ALPS (Algorithms and Libraries for Physics Simulations) project, an international open source software project to develop libraries and application programs for the simulation of strongly correlated quantum lattice models such as quantum magnets, lattice bosons, and strongly correlated fermion systems. Development is centered on common XML and binary data formats, on libraries to simplify and speed up code development, and on full-featured simulation programs. The programs enable non-experts to start carrying out numerical simulations by providing basic implementations of the important algorithms for quantum lattice models: classical and quantum Monte Carlo (QMC) using non-local updates, extended ensemble simulations, exact and full diagonalization (ED), as well as the density matrix renormalization group (DMRG). Changes in the new release include a DMRG program for interacting models, support for translation symmetries in the diagonalization programs, the ability to define custom measurement operators, and support for inhomogeneous systems, such as lattice models with traps. The software is available from our web server at http://alps.comp-phys.org/ .

cond-mat.str-el↗

arXiv2007

Electronic Properties of the Semiconductor RuIn$_3$

Temperature dependent measurements of the resistivity on RuIn$_3$ single crystals show a semiconducting behaviour, in contrast to previously published results. In the high temperature range the semiconducting gap was measured to be $0.4-0.5$eV. We observe an anisotropy of the resistivity along [110] and [001] orientations of the tetragonal single crystals. At low temperatures two activation energies of impurities were estimated to 1meV and 10meV. The temperature dependence of the specific heat and the band structure calculations provide also a semiconducting behaviour of RuIn$_3$.

cond-mat.mtrl-sci↗

arXiv2001

The LDA+DMFT Approach to Materials with Strong Electronic Correlations

LDA+DMFT is a novel computational technique for ab initio investigations of real materials with strongly correlated electrons, such as transition metals and their oxides. It combines the strength of conventional band structure theory in the local density approximation (LDA) with a modern many-body approach, the dynamical mean-field theory (DMFT). In the last few years LDA+DMFT has proved to be a powerful tool for the realistic modeling of strongly correlated electronic systems. In this paper the basic ideas and the set-up of the LDA+DMFT(X) approach, where X is the method used to solve the DMFT equations, are discussed. Results obtained with X=QMC (quantum Monte Carlo) and X=NCA (non-crossing approximation) are presented and compared. By means of the model system La$_{1-x}$Sr$_{x}$TiO$_{3}$ we show that the method X matters qualitatively and quantitatively. Furthermore, we discuss recent results on the Mott-Hubbard metal-insulator transition in the transition metal oxide V$_2$O$_3$ and the $α$-$γ$ transition in the 4f-electron system Ce.

cond-mat.str-el↗

arXiv2000

Metal insulator transition in TlSr2CoO5 from orbital degeneracy and spin disproportionation

To describe the metal insulator transition in the new oxide TlSr2CoO5 we investigate its electronic structure by LDA and model Hartree-Fock calculations. Within LDA we find a homogeneous metallic and ferromagnetic ground state, but when including the Coulomb interaction more explicitly within the Hartree-Fock approximation, we find an insulating state of lower energy with both spin and orbital order. We also interpret our results in terms of a simple model.

cond-mat.str-el↗

arXiv1999

The electronic structure of the heavy fermion metal $LiV_2O_4$

The electronic structure of the first reported heavy fermion compound without f-electrons LiV_2O_4 was studied by an ab-initio calculation method. In the result of the trigonal splitting and d-d Coulomb interaction one electron of the $d^{1.5}$ configuration of V ion is localized and the rest partially fills a relatively broad conduction band. The effective Anderson impurity model was solved by Non-Crossing-Approximation method, leading to an estimation for the single-site Kondo energy scale T_K. Then, we show how the so-called exhaustion phenomenon of Nozières for the Kondo lattice leads to a remarkable decrease of the heavy-fermion (or coherence) energy scale $T_{coh}\equiv {T_K}^2/D$ (D is the typical bandwidth), comparable to the experimental result.

cond-mat.str-el↗

arXiv1998

Nonlocal Dynamical Correlations of Strongly Interacting Electron Systems

We introduce an extension of the dynamical mean field approximation (DMFA) which retains the causal properties and generality of the DMFA, but allows for systematic inclusion of non-local corrections. Our technique maps the problem to a self-consistently embedded cluster. The DMFA (exact result) is recovered as the cluster size goes to one (infinity). As a demonstration, we study the Falicov-Kimball model using a variety of cluster sizes. We show that the sum rules are preserved, the spectra are positive definite, and the non-local correlations suppress the CDW transition temperature. \

cond-mat.str-el↗

arXiv1996

Effects of spin fluctuations in the t-J model

Recent experiments on the Fermi surface and the electronic structure of the cuprate-supercondutors showed the importance of short range antiferromagnetic correlations for the physics in these systems. Theoretically, features like shadow bands were predicted and calculated mainly for the Hubbard model. In our approach we calculate an approximate selfenergy of the $t$-$J$ model. Solving the $U=\infty$ Hubbard model in the Dynamical Mean Field Theory (DMFT) yields a selfenergy that contains most of the local correlations as a starting point. Effects of the nearest neighbor spin interaction $J$ are then included in a heuristical manner. Formally like in $J$-perturbation theory all ring diagrams, with the single bubble assumed to be purely local, are summed to get a correction to the DMFT-self engergy This procedure causes new bands and can furnish strong deformation of quasiparticle bands. % Our results are finally compared with %former approaches to the Hubbard model.

cond-mat↗

arXiv1993

Functional Integral Approach to the Single Impurity Anderson Model

Recently, a functional integral representation was proposed by Weller (Weller, W.: phys.~stat.~sol.~(b) {\bf 162}, 251 (1990)), in which the fermionic fields strictly satisfy the constraint of no double occupancy at each lattice site. This is achieved by introducing spin dependent Bose fields. The functional integral method is applied to the single impurity Anderson model both in the Kondo and mixed-valence regime. The f-electron Green's function and susceptibility are calculated using an Ising-like representation for the Bose fields. We discuss the difficulty to extract a spectral function from the knowledge of the imaginary time Green's function. The results are compared with NCA calculations.

cond-mat↗