Nesting Induced Peierls-type Instability for Compressed Li-CI16

TL;DR

This paper investigates how pressure-induced Fermi surface deformation in lithium leads to a Peierls-type instability, explaining the emergence of the complex cI16 structure and its relation to superconductivity enhancement.

Contribution

It introduces a theoretical analysis linking Fermi surface nesting to structural instability in compressed lithium, proposing a Peierls-type mechanism for the cI16 phase.

Findings

Fermi surface becomes more anisotropic under pressure

Nesting along the bcc [121] direction develops

Phonon instability at N explains cI16 stability

Abstract

Alkalies are considered to be simple metals at ambient conditions. However, recently reported theoretical and experimental results have shown an unexpected and intriguing correlation between complex structures and an enhanced superconducting transition temperature in lithium under pressure. In this article we analyze the pressure induced Fermi surface deformation in bcc lithium, and its relation to the observed cI16 structure. According to our calculations, the Fermi surface becomes increasingly anisotropic with pressure and develops an extended nesting along the bcc [121] direction. This nesting induces a phonon instability of both transverse modes at N, so that a Peierls-type mechanism is proposed to explain the stability of Li-cI16.