On a Second Critical Point in the First Order Metal - Insulator Transitions

TL;DR

This paper reveals a second critical point in first order metal-insulator transitions where the dielectric constant becomes negative, significantly affecting reflectivity and phase behavior, supported by theoretical modeling and experimental data.

Contribution

It introduces the concept of a second critical point with negative dielectric constant in first order metal-insulator transitions, supported by dielectric function analysis and experimental validation.

Findings

Identification of a second critical point where dielectric constant turns negative

Experimental validation using MnO data showing two critical points

Discussion of phase separation and its implications in different systems

Abstract

For the first order Metal Insulator Transitions we show that together with the d.c conductance zero there is a second critical point, where the dielectric constant becomes zero and further turns negative. At this point the metallic reflectivity sharply increases. The two points can be separated by a Phase Separation State in a 3D disordered system, but may tend to merge in 2D. For illustration we evaluate the dielectric function in a simple effective medium approximation and show that at the second point it turns negative. We reproduce the experimental data on a typical Mott insulator like MnO, demonstrating the presence of the two points clearly. We discuss other experiments for studies of the phase separation state and a similar phase separation in superconductors with insulating inclusions.