U(1) Dirac spin liquid in a magnetic field: emergent gauge fluxes and dynamical signatures

Quantum spin liquids are exotic states of matter where spins fractionalize into spinons coupled to emergent gauge fields. A particularly fascinating example is the U(1) Dirac spin liquid. Its low-energy theory, emergent quantum electrodynamics (QED₃), is believed to flow to a strongly coupled conformal fixed point. Motivated by recent numerical evidence for its realization in microscopic models of frustrated magnets as well as the identification of several candidate materials, we revisit the problem of the U(1) DSL in a Zeeman magnetic field, which has been suggested to exhibit antiferromagnetic ordering. We investigate experimentally observable phenomena associated with deforming the underlying conformal field theory. Using a combination of field-theoretic analysis and sign-problem free Monte Carlo simulations of a U(1) lattice gauge theory, we detail signatures in the dynamical spin-structure factor, and discuss observables that may be unique to such field-induced state. In experiments, these may allow one to infer the presence of an underlying DSL at zero field.