Kondo signatures in Dirac spin liquids: Non-Abelian bosonization after Chern-Simons fermionization

Quantum impurities serve as in-situ probes of the frustrated quantum magnets, and Dirac spin liquids are an important class of quantum spin liquids. Here, we present a general method, a combination of the Chern-Simons fermionization and the Wess-Zumino-Witten theory, to study the quantum impurity in Dirac spin liquids. Under the Chern-Simons fermionization, the gauge fluctuations are apparently suppressed and the low-energy physics is described by a number of Dirac valleys with valley-dependent pseudospin-momentum locking. The (2+1)D effective theory can be further reduced into the (1+1)D Wess-Zumino-Witten theory by rotational symmetry, where the pseudospin-exchange between Dirac fermions and the impurity can then be solved by the non-Abelian bosonization. Consequently, fixed points of Fermi liquid and non-Fermi liquid are identified, respectively, depending on the relevance of the impurity scattering among the Dirac valleys. This leads to experimental fingerprints for Dirac spin liquids, including a Kondo-induced magneto-thermal effect, a non-monotonous thermal conductivity during the crossover, and an anisotropic spin correlation function.