title: Quantum transitions driven by one-bond defects in quantum Ising rings.
abstract: We investigate quantum scaling phenomena driven by lower-dimensional defects in quantum Ising-like models. We consider quantum Ising rings in the presence of a bond defect. In the ordered phase, the system undergoes a quantum transition driven by the bond defect between a magnet phase, in which the gap decreases exponentially with increasing size, and a kink phase, in which the gap decreases instead with a power of the size. Close to the transition, the system shows a universal scaling behavior, which we characterize by computing, either analytically or numerically, scaling functions for the low-level energy differences and the two-point correlation function. We discuss the implications of these results for the nonequilibrium dynamics in the presence of a slowly varying parallel magnetic field h, when going across the first-order quantum transition at h=0.
authors.affiliation: Dipartimento di Fisica dell'Università di Pisa and INFN, Largo Pontecorvo 3, I-56127 Pisa, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Campostrini
authors.affiliation: Dipartimento di Fisica di "Sapienza" Università di Roma and INFN, Sezione di Roma I, I-00185 Roma, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Pelissetto
authors.affiliation: Dipartimento di Fisica dell'Università di Pisa and INFN, Largo Pontecorvo 3, I-56127 Pisa, Italy.
authors.forename: Ettore
authors.initials: E
authors.lastname: Vicari