Abstract
For quantum critical spin chains without disorder, it is known that the entanglement of a segment of spins with the remainder is logarithmic in with a prefactor fixed by the central charge of the associated conformal field theory. We show that for a class of strongly random quantum spin chains, the same logarithmic scaling holds for mean entanglement at criticality and defines a critical entropy equivalent to central charge in the pure case. This effective central charge is obtained for Heisenberg, , and quantum Ising chains using an analytic real-space renormalization-group approach believed to be asymptotically exact. For these random chains, the effective universal central charge is characteristic of a universality class and is consistent with a -theorem.
- Received 29 June 2004
DOI:https://doi.org/10.1103/PhysRevLett.93.260602
©2004 American Physical Society