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TT: Fachverband Tiefe Temperaturen
TT 51: Correlated Electrons: Method Development II
TT 51.9: Vortrag
Mittwoch, 11. März 2026, 17:15–17:30, HSZ/0101
A Quasiparticle Excitation Ansatz for 2D Isometric Tensor Network States — •Lukas Wittmann1,2, Johannes Hauschild1,2, and Frank Pollmann1,2 — 1Technical University of Munich, TUM School of Natural Sciences, Physics Department, 85748 Garching, Germany — 2Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, 80799 München, Germany
Isometric tensor network states (isoTNS) in 2D were introduced as a subclass of projected entangled pair states (PEPS) with additional isometry conditions that allow for an efficient evaluation of local expectation values [1]. Based on a formulation in a finite 45 ∘-rotated square lattice [2], we introduce an ansatz for quasiparticles in the tangent space of an isoTNS [3,4], generalizing the ideas from 1D matrix product states (MPS) [5,6] and infinite PEPS [7]. We show that this ansatz can faithfully represent low-energy excitations with standing waves of spin flips, crucial for the dynamical structure factor, and discuss an algorithm to variationally optimize them.
[1] M.P. Zaletel, F. Pollmann, Phys. Rev. Lett. 124, 037201 (2020)
[2] B. Sappler et al., arXiv:2507.08080
[3] L. Wittmann, Master’s Thesis,
https://github.com/lukasjwittmann/iso_tns-public
[4] L. Wittmann, J. Hauschild, F. Pollmann, in preparation
[5] J. Haegeman et al., Phys. Rev. B 88, 075133 (2013)
[6] M. Van Damme et al., Phys. Rev. B 104, 115142 (2021)
[7] L. Vanderstraeten et al., Phys. Rev. B 92, 201111 (2015)
Keywords: projected entangled pair states (PEPS); isometric tensor network states (isoTNS); tangent space; variational quasiparticle ansatz; low-energy excitations