Regensburg 2010 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 27: CE: Poster Session
TT 27.43: Poster
Wednesday, March 24, 2010, 14:00–18:00, Poster D1
Variational matrix product states for nano chains — •Andrej Schwabe and Michael Potthoff — I. Institut für Theoretische Physik, Universität Hamburg, Hamburg, Germany
We discuss a variational matrix product states (VMPS)[1,2] code, where the coefficients of the test wave function Ψ are assumed as product of site dependent matrices Ai. The advantageous matrix product operator (MPO) representations is used, which allows to construct a generic algorithm, almost independent of the Hamiltonian H. In order to optimize the code and to account for physical properties of H, the wave function transformation as well as U(1) symmetries have been implemented. Furthermore, the corrected one-site algorithm, recently proposed by White [3], is incorporated in our VMPS code at several approximation stages. We perform a benchmark test to study the impact of both the corrected one-site algorithm and the implementation of the U(1) symmetries on CPU time and accuracy of the results.
The technique is applied to ferromagnetic nano chains in one dimension, described by inhomogeneous Hubbard-type models with site dependent Hubbard-U. The magnetic phase diagram and its dependence on the chain length are investigated. We discuss the emergence of the magnetic exchange coupling (e.g. RKKY) within and between the nano particles. Size and distance dependencies are studied as well as the competition with the Kondo effect.
[1] U. Schollwöck, Rev. Mod. Phys. 77, 259 (2005)
[2] F. Verstraete et al., Advances in Physics 57, 143 (2008)
[3] S. R. White, Phys. Rev. B 72, 180403 (2005)