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arXiv · 2606.23117

Angular-time evolution and edge-spin dynamics in the Haldane phase of the S=1 bilinear-biquadratic chain

Takuma Kaise·Kouichi Okunishi
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Abstract

We investigate the angular-time evolution -- a parameter-time evolution generated by the entanglement Hamiltonian -- for the bipartitioned ground state of the S=1 bilinear-biquadratic chain under the open boundary condition with the up edge spin. Using a matrix-product-state representation of the ground-state wavefunction, we calculate the angular-time spin correlation functions $\langle S_n^{\alpha }(\tau )S_{n'}^{\alpha }(0)\rangle$ in the Haldane phase, and extract its dominant oscillation mode attributed to the nearly two-fold-degenerate entanglement spectrum associated with the $\mathbb{Z}_2 \times \mathbb{Z}_2$ symmetry. We also compute the effective edge-spin dynamics under a uniform magnetic field applied to the system part and numerically verify its correspondence to the dominant angular-time mode by precisely comparing the subsystem-size dependence of their amplitudes.

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Takuma Kaise, Kouichi Okunishi. 2026-06-22. Angular-time evolution and edge-spin dynamics in the Haldane phase of the S=1 bilinear-biquadratic chain. https://arxiv.org/abs/2606.23117

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