Robustness of SO(5)-Haldane and intermediate-Haldane phases in spin-2 quantum chains

Augustine Kshetrimayum and Román Orús

The existence of an Intermediate Haldane phase for a spin-2 Heisenberg chain was suggested by 
Oshikawa in 1992[1]. However, the evidence for its existence has remained quite elusive. In a 
recent paper [2] it was proven that such a phase exists in a family of generalized spin-2 quantum 
Heisenberg chains. In this work, we study the robustness of this phase for generalized spin-2 
quantum Heisenberg chains with uniaxial anisotropy, and in the thermodynamic limit. We find very 
robust symmetry-protected topologically ordered SO(5)-Haldane and intermediate-Haldane phases, 
which we assess by a variety of methods including the entanglement spectrum of the system and the 
behavior of string-order parameters. Moreover, we study time-evolution properties of these phases. 
Our numerical results are based on using Matrix Product States (MPS) to represent the wave 
function, in combination with the infinite Time-Evolving Block Decimation (iTEBD) method.