Pressure-induced metal-insulator and spin-state transition in low-valence layered nickelates

TL;DR

This paper predicts a pressure-induced transition from insulator to metal and a spin-state change in layered nickelates, supported by ab initio calculations, revealing how pressure influences electronic and magnetic states.

Contribution

It introduces a theoretical prediction of a pressure-driven metal-insulator and spin-state transition in La4Ni3O8, extending understanding of correlated electron behavior under pressure.

Findings

Pressure favors metallic low-spin state at 5 GPa.

Spin-state transition temperature decreases with pressure.

Similar physics may occur in La3Ni2O6 but on a different energy scale.

Abstract

Ab initio calculations predict a metal-insulator transition at zero temperature to occur in La$_4$Ni$_3$O$_8$ at moderate pressures as a result of a pressure-induced spin-state transition. The spin-state transition that is seen at 105 K at ambient pressure from a low-temperature high-spin state to a high-temperature low-spin state has been observed to be shifted to lower temperatures as pressure is applied. From our calculations we find that a smaller unit cell volume favors the metallic low-spin state, which becomes more stable at 5 GPa. Similar physics should take place in the related compound La$_3$Ni$_2$O$_6$, but on a different energy scale, which may account for why the transition has not been observed in this material.