Defect production due to quenching through a multicritical point

Abstract

We study the generation of defects when a quantum spin system is quenched through a multicritical point by changing a parameter of the Hamiltonian as t/τ, where τ is the characteristic timescale of quenching. We argue that when a quantum system is quenched across a multicritical point, the density of defects (n) in the final state is not necessarily given by the Kibble–Zurek scaling form n~1/τdν/(zν+1), where d is the spatial dimension, and ν and z are respectively the correlation length and dynamical exponent associated with the quantum critical point. We propose a generalized scaling form of the defect density given by n~1/τd/(2z2), where the exponent z2 determines the behavior of the off-diagonal term of the 2 × 2 Landau–Zener matrix at the multicritical point. This scaling is valid not only at a multicritical point but also at an ordinary critical point.