Groundstate factorization and quantum phase transition in spin chains
by
Prof.Gian Luca Giorgi(IFISC (UIBCSIC) Instituto de Física Interdisciplinar y Sistemas Complejos, Campus Universitat de les Illes Balears, E07122 Palma de Mallorca, Spain)
→
Europe/Rome
Aula 7 (Dipartimento di Fisica - E. E.Fermi)
Aula 7
Dipartimento di Fisica - E. E.Fermi
Description
I will discuss the problem of ground state factorization in spin chains. After a general introduction
about the topic, I will describe in detail the case of the XY chain in a transverse field. It will be shown
that the factorized ground state is an accidental degeneracy of the Hamiltonian. A finitesize
analysis
allows one to establish the cause of the existence of different regimes in the symmetrybroken
phase
and to emphasize the role of the factorizing field in the process. In the second part of the seminar, I will
extend the study to dimerized chains, where, together with the usual ferromagnetic and
antiferromagnetic regimes, a third case emerges, consisting of an antiferromagnetic Neéltype
ground
state whose unitary cell is represented by a pairs of spins. As in the regular XY model, the factorizing
field represents a border line between region exhibiting different symmetrybreaking
mechanisms