Spatial behavior in a Mott insulator near the voltage-driven resistive transition

TL;DR

This paper develops a real space theoretical framework to understand how a voltage bias induces spatial and magnetic changes in a Mott insulator, revealing a transition to metallic states as voltage increases.

Contribution

It introduces a self-consistent Keldysh mean field approach to analyze voltage-driven transitions in a Mott insulator, including spatial modulation and phase changes.

Findings

Charge and spin profiles become spatially modulated near edges at finite bias.

Conductance remains zero and current is exponentially suppressed below threshold voltage.

Beyond the threshold, the system transitions to an inhomogeneous antiferromagnetic metal and eventually a paramagnetic metal.

Abstract

We develop a real space theory of the voltage bias driven transition from a Mott insulator to a correlated metal. Within our Keldysh mean field approach the problem reduces to a self-consistency scheme for the charge and spin profiles in this open system. We solve this problem for a two dimensional antiferromagnetic Mott insulator at zero temperature. The charge and spin magnitude is uniform over the system at zero bias, but a bias $V$ leads to spatial modulation over a lengthscale $\xi(V)$ near the edges. $\xi(V)$ grows rapidly and becomes comparable to system size as $V$ increases towards a threshold scale $V_c$. The linear response conductance of the insulator is zero with the current being exponentially small for $V \ll V_c$. The current increases rapidly as $V \rightarrow V_c$. Beyond $V_c$, we observe an inhomogeneous low moment antiferromagnetic metal, and at even larger bias a current saturated paramagnetic metal. We suggest an approximate scheme for the spectral features of this nonequilibrium system.