Transition from a Dirac spin liquid to an antiferromagnet: Monopoles in a QED(3)-Gross-Neveu theory

摘要

We study the quantum phase transition from a Dirac spin liquid to an antiferromagnet driven by condensing monopoles with spin quantum numbers. We describe the transition in field theory by tuning a fermion interaction to condense a spin-Hall mass, which in turn allows the appropriate monopole operators to proliferate and confine the fermions. We compute various critical exponents at the quantum critical point (QCP), including the scaling dimensions of monopole operators by using the state-operator correspondence of conformal field theory. We find that the degeneracy of monopoles in QED(3) is lifted and yields a nontrivial monopole hierarchy at the QCP. In particular, the lowest monopole dimension is found to be smaller than that of QED(3) using a large-N-f expansion, where 2N(f) is the number of fermion flavors. For the minimal magnetic charge, this dimension is 0.39N(f) at leading order. We also study the QCP between Dirac and chiral spin liquids, which allows us to test a conjectured duality to a bosonic CP1 theory. Finally, we discuss the implications of our results for quantum magnets on the kagome lattice.