Entanglement in first excited states of some many-body quantum spin systems: indication of quantum phase transition in finite size systems

12 Nov 2020 Biswas George Biswas Anindya

We compute concurrence, a measure of bipartite entanglement, of the first excited state of the $1$-D Heisenberg frustrated $J_1$-$J_2$ spin-chain and observe a sudden change in the entanglement of the eigen state near the coupling strength $\alpha=J_2/J_1\approx0.241$, where a quantum phase transition from spin-fluid phase to dimer phase has been previously reported. We numerically observe this phenomena for spin-chain with $8$ sites to $16$ sites, and the value of $\alpha$ at which the change in entanglement is observed asymptotically tends to a value $\alpha_c\approx0.24116$... (read more)

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