Gapless quantum spin chains: Multiple dynamics and conformal wavefunctions

Xiao Chen, Eduardo Fradkin, William Witczak-Krempa

Research output: Contribution to journalArticlepeer-review


We study gapless quantum spin chains with spin 1/2 and 1: the Fredkin and Motzkin models. Their entangled groundstates are known exactly but not their excitation spectra. We first express the groundstates in the continuum which allows for the calculation of spin and entanglement properties in a unified fashion. Doing so, we uncover an emergent conformal-type symmetry, thus consolidating the connection to a widely studied family of Lifshitz quantum critical points in 2d. We then obtain the low lying excited states via large-scale DMRG simulations and find that the dynamical exponent is in both cases. Other excited states show a different z, indicating that these models have multiple dynamics. Moreover, we modify the spin-1/2 model by adding a ferromagnetic Heisenberg term, which changes the entire spectrum. We track the resulting non-trivial evolution of the dynamical exponents using DMRG. Finally, we exploit an exact map from the quantum Hamiltonian to the non-equilibrium dynamics of a classical spin chain to shed light on the quantum dynamics.

Original languageEnglish (US)
Article number464002
JournalJournal of Physics A: Mathematical and Theoretical
Issue number46
StatePublished - Oct 23 2017


  • Lifshitz quantum field theory
  • non-equilibrium relaxation
  • orbifolds
  • quantum dynamics, conformal symmetry
  • quantum entanglement
  • quantum spin chains

ASJC Scopus subject areas

  • Statistical and Nonlinear Physics
  • Statistics and Probability
  • Modeling and Simulation
  • Mathematical Physics
  • General Physics and Astronomy


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