Raman signature of the U(1) Dirac spin-liquid state in the spin-1/2 kagome system

Citation Ko, Wing-Ho et al. " Raman signature of the U(1) Dirac spin-liquid state in the spin-1/2 kagome system. Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. We followed the Shastry-Shraiman formulation of Raman scattering in Hubbard systems and considered the Raman intensity profile in the spin-1 2 " perfect " kagome lattice herbertsmithite ZnCu 3 ͑OH͒ 6 Cl 2 , assuming the ground state is well-described by the U͑1͒ Dirac spin-liquid state. In the derivation of the Raman T matrix, we found that the spin-chirality term appears in the A 2g channel in the kagome lattice at the t 4 / ͑␻ i − U͒ 3 order, but ͑contrary to the claims by Shastry and Shraiman͒ vanishes in the square lattice to that order. In the ensuing calculations on the spin-1 2 kagome lattice, we found that the Raman intensity profile in the E g channel is invariant under an arbitrary rotation in the kagome plane, and that in all ͑A 1g , E g , and A 2g ͒ symmetry channels the Raman intensity profile contains broad continua that display power-law behaviors at low energy, with exponent approximately equal to 1 in the A 2g channel and exponent approximately equal to 3 in the E g and the A 1g channels. For the A 2g channel, the Raman profile also contains a characteristic 1 / ␻ singularity, which arose in our model from an excitation of the emergent U͑1͒ gauge field.