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MA: Fachverband Magnetismus

MA 41: Poster III

MA 41.24: Poster

Donnerstag, 20. März 2025, 15:00–17:30, P3

Finite-temperature DMRG calculations for big spin systems using matrix product states — •Lukas Horstmann and Jürgen Schnack — University of Bielefeld, Bielefeld, Germany

Doing finite-temperature calculations on bigger spin systems is often limited by the size of the Hilbert spaces being too large for algorithms such as exact diagonalisation or finite-temperature Lanczos. In order to work around this problem White proposed a method based on the Density Matrix Renormalization Group (DMRG) in the late 90th which allows the calculation of bigger systems by applying multiple local optimisation steps while truncating the size of the Hilbert space by a large amount without loosing too much information about the system. This method works, but it is slow. Therefore, the whole method was translated into a tensor representation using matrix product states where the full system and its operators are described by a tensor network which allows faster linear algebra calculations [1]. In this contribution we will expand this method to finite-temperature calculations using imaginity-time evolution with TenPy [2] to calculate thermodynamic properties for larger spin systems.

[1] Ulrich Schollwöck, doi: 10.1016/j.aop.2010.09.012

[2] Johannes Hauschild, Frank Pollmann, doi: 10.21468/SciPostPhysLectNotes.5

Keywords: DMRG; Finite Temperature; Matrix Product States; Matrix Product Operators; Imaginary time evolution