The Anderson-Mott transition induced by hole-doping in Nd1-xTiO3

TL;DR

This study investigates the insulator-metal transition in Nd1-xTiO3 caused by hole-doping, revealing a complex phase diagram with Anderson localization, Fermi-liquid metallic behavior, and the suppression of magnetic order, differing from similar calcium-doped systems.

Contribution

It provides a detailed phase diagram of Nd1-xTiO3 showing the evolution from insulator to metal and highlights the role of Anderson localization and electronic correlations in this transition.

Findings

Insulating behavior for x < 0.071

Anderson localization dominates for 0.074 < x < 0.089

Fermi-liquid metallic behavior observed for 0.095 < x < 0.203

Abstract

The insulator/metal transition induced by hole-doping due to neodymium vacancies of the Mott- Hubbard antiferromagnetic insulator, Nd1-xTiO3, is studied over the composition range 0.010(6) < x < 0.243(10). Insulating p-types conduction is found for x < 0.071(10). Anderson localization in the presence of a Mott-Hubbard gap, is the dominant localization mechanism for the range of 0.074(10) < x < 0.089(1) samples. For x < 0.089(1), n-type conduction is observed and the activation energy extrapolates to zero by x < 0.1. The 0.095(8) < x < 0.203(10) samples are Fermi-liquid metals and the effects of strong electronic correlations are evident near the metal-to-insulator boundaries in features such as large Fermi liquid T2 coefficients. For 0.074(9) < x < 0.112(4), a weak negative magnetoresistance is found below ~ 15 K and it is attributed to the interaction of conduction electrons with Nd3+ magnetic moments. Combining information from our companion study of the magnetic properties of Nd1-xTiO3 solid solution, a phase diagram is proposed. The main conclusions are that long range antiferromagnetic order disappears before the onset of metallic behavior and that the Anderson-Mott transition occurs over a finite range of doping levels. Our results differ from conclusions drawn from a similar study on the hole doped Nd1-xCaxTiO3 system which found the co-existence of antiferromagnetic order and metallic behavior and that the Mott transition occurs at a discrete doping level.