To attend this Zoom seminar, please contact Vadim Oganesyan.
Kevin Beach, University of Mississippi
I will discuss the case of spin-half chains whose interactions are pairwise ferromagnetic but contingent on the spin state at a third adjacent site. The resulting family of Hamiltonians, which includes the Fredkin spin chain and its t-deformed cousins, is frustration-free but highly nontrivial. The phase diagram includes states with large entanglement and unusually slow dynamics. At the Fredkin point, the low-energy physics is that of a strong xy ferromagnet with gapless excitations. The excitations, however, are distinct from conventional spin waves. Instead, the object of interest is a delocalized bonded spin pair that must drag itself through the effective medium of the background spins: there is a topological character that must be preserved during the motion that induces a form of dynamical jamming. In addition to some new analytical results, I will present numerical results that explore the broader phase diagram (DMRG) and that directly simulate the quantum dynamics of the various excitations (QMC).