Quantum inductance and negative electrochemical capacitance at finite frequency

TL;DR

This paper theoretically investigates how quantum capacitance varies with frequency, revealing that quantum inductance can cause negative electrochemical capacitance due to phase lag in electron dynamics.

Contribution

It introduces a classical RLC circuit model to describe frequency-dependent quantum capacitance, highlighting the role of quantum inductance in electron phase delay.

Findings

Quantum inductance is proportional to electron dynamics time scale.

Negative effective capacitance can occur at finite frequency.

Phase delay in current leads to negative capacitance effects.

Abstract

We report on theoretical investigations of frequency dependent quantum capacitance. It is found that at finite frequency a quantum capacitor can be characterized by a classical RLC circuit with three parameters: a static electrochemical capacitance, a charge relaxation resistance, and a quantum inductance. The quantum inductance is proportional to the characteristic time scale of electron dynamics and due to its existence, the time dependent current can accumulate a phase delay and becomes lagging behind the applied ac voltage, leading to a negative effective capacitance.