Drude weight in systems with open boundary conditions

A many-electron conducting system undergoes free acceleration in response to a macroscopic field. The Drude weight D-also called charge stiffness-measures the adiabatic (inverse) inertia of the electrons; the D formal expression requires periodic boundary conditions. When instead a bounded sample is addressed within open boundary conditions, no current flows and a constant (external) field only polarizes the sample: the Faraday cage effect. Nonetheless, a low-frequency field induces forced oscillations: We show here that the low-frequency linear response of the bounded system is dominated by the adiabatic inertia and allows an alternative evaluation of D. Simulations on model one-dimensional systems demonstrate our main message.