Many-body spectral functions from steady state density functional theory

TL;DR

This paper introduces a method to derive the many-body spectral function of interacting electrons from equilibrium DFT calculations using a specialized setup and the steady-state i-DFT formalism, enabling accurate spectral analysis.

Contribution

It presents a novel approach combining an STM-like setup with steady-state DFT to extract many-body spectral functions from equilibrium calculations.

Findings

Exact relation between interacting and Kohn-Sham spectral functions derived.

Application to Anderson impurity and Constant Interaction models demonstrated.

Method enables spectral function extraction from equilibrium DFT data.

Abstract

We propose a scheme to extract the many-body spectral function of an interacting many-electron system from an equilibrium density functional theory (DFT) calculation. To this end we devise an ideal STM-like setup and employ the recently proposed steady-state DFT formalism (i-DFT) which allows to calculate the steady current through a nanoscopic region coupled to two biased electrodes. In our setup one of the electrodes serves as a probe ('STM tip'), which is weakly coupled to the system we want to measure. In the ideal STM limit of vanishing coupling to the tip, the system is restored to quasi-equilibrium and the normalized differential conductance yields the exact equilibrium many-body spectral function. Calculating this quantity from i-DFT, we derive an exact relation expressing the interacting spectral function in terms of the Kohn-Sham one. As illustrative examples we apply our scheme to calculate the spectral functions of two non-trivial model systems, namely the single Anderson impurity model and the Constant Interaction Model.