Topology in Free Fermion Systems
نویسندگان
چکیده
We study the relationship between bipartite entanglement, subsystem particle number and topology in a half-filled free fermion system. It is proposed that the spin-projected particle numbers can distinguish the quantum spin Hall state from other states, and can be used to establish a new topological index for the system. Furthermore, we apply the new topological invariant to disordered system and show that a topological phase transition occurs when the disorder strength is increased beyond a critical values. It is also shown that the subsystem particle number fluctuation displays behavior very similar to the entanglement entropy. It provides a lower-bound estimation for the entanglement entropy, which can be utilized to obtain an estimate of the entanglement entropy experimentally. Entanglement, Subsystem Particle Numbers and Topology in Free Fermion Systems 2
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