Evidence of Two Distinct Dynamic Critical Exponents in Connection with Vortex Physics

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The dynamic critical exponent z is determined from numerical simulations for the three-dimensional (3D) lattice Coulomb gas (LCG) and the 3D XY models with relaxational dynamics. It is suggested that the dynamics is characterized by two distinct dynamic critical indices z₀ and z related to the divergence of the relaxation time τ by τ∝ ξᶻ⁰ and τ∝ k⁻ᶻ, where ξ is the correlation length and k the wavevector. The values determined are z₀≈ 1.5 and z≈ 1 for the 3D LCG and z₀≈ 1.5 and z≈ 2 for the 3D XY model. It is argued that the nonlinear IV exponent relates to z₀, whereas the usual Hohenberg-Halperin classification relates to z. Possible implications for the interpretation of experiments are pointed out. Comparisons with other existing results are discussed.