Thermal Drude weight in an integrable chiral clock model

Abstract

We calculate the finite temperature thermal conductivity of a time-reversal invariant chiral $\mathbb{Z}_3$ clock model along an integrable line in the parameter space using tDMRG. The thermal current itself is not a conserved charge, unlike in the XXZ model, but has a finite overlap with a local conserved charge $Q^{(2)}$ obtained from the transfer matrix. We find that the Drude weight is finite at non-zero temperature, and the Mazur bound from $Q^{(2)}$ saturates the Drude weight, allowing us to obtain an asymptotic expression for the Drude weight at high temperatures. The numerical estimates are validated using a sum rule for thermal conductivity. On the computational side, we also explore the effectiveness of the ancilla disentangler in the integrable and non-integrable regimes of the model. We find that the disentangler helps in localizing the entanglement growth around the quench location, but the improvement is lesser in the non-integrable regime and at low temperatures.