Finite-size scaling of the entanglement entropy of the quantum Ising chain with homogeneous, periodically modulated and random couplings

Understand

Using free-fermionic techniques we study the entanglement entropy of a block of contiguous spins in a large finite quantum Ising chain in a transverse field, with couplings of different types: homogeneous, periodically modulated and random.

• We carry out a systematic study of finite-size effects at the quantum critical point, and evaluate subleading corrections both for open and for periodic boundary conditions.
• For a block corresponding to a half of a finite chain, the position of the maximum of the entropy as a function of the control parameter (e.g.
• the transverse field) can define the effective critical point in the finite sample.