Quantum many-body scars in spin-1 Kitaev chains

To provide a physical example of quantum scars, we study the many-body scars in the spin-1 Kitaev chain where the so-called PXP Hamiltonian is exactly embedded in the spectra. Regarding the conserved quantities, the Hilbert space is fragmented into disconnected subspaces and we explore the associated constrained dynamics. The continuous revivals of the fidelity and the entanglement entropy when the initial state is prepared in vertical bar Z(k)) (k = 2, 3) state illustrate the essential physics of the PXP model. We study the quantum phase transitions in the one-dimensional spin-1 Kitaev-Heisenberg model using the density-matrix renormalization group and Lanczos exact diagonalization methods, and determine the phase diagram. We parametrize the two terms in the Hamiltonian by the angle phi, where the Kitaev term is K = sin(phi) and competes with the Heisenberg J = cos(phi) term. One finds a rich ground-state phase diagram as a function of the angle phi. Depending on the ratio K/J = tan(phi), the system either breaks the symmetry to one of distinct symmetry broken phases, or preserves the symmetry in a quantum spin-liquid phase with frustrated interactions. We find that the scarred state is stable for perturbations which obey Z(2)-symmetry, while it becomes unstable against Heisenberg-type perturbations.

Automated summary

This study provides a physical example of quantum scars by investigating the many-body scars in the spin-1 Kitaev chain. The essential physics of the PXP model is illustrated through the continuous revivals of fidelity and entanglement entropy. Quantum phase transitions in the one-dimensional spin-1 Kitaev-Heisenberg model are studied using density-matrix renormalization group and Lanczos exact diagonalization methods, resulting in a rich ground-state phase diagram. The stability of the scarred state is found to depend on perturbations obeying Z(2)-symmetry, while becoming unstable against Heisenberg-type perturbations.