Quantum Oscillations of Elastic Moduli and Softening of Phonon Modes in Metals

TL;DR

This paper theoretically investigates how strong magnetic fields induce quantum oscillations in elastic moduli of metals, revealing potential phonon mode softening and lattice instabilities, especially in metals with cylindrical Fermi surface segments.

Contribution

It introduces a theoretical framework linking magnetostriction-induced quantum oscillations to phonon softening and lattice instability in metals with specific Fermi surface geometries.

Findings

Significant softening of acoustic modes near quantum oscillation peaks.

Magnetic instability can lead to lattice instability in certain metals.

Cylindrical Fermi surface segments favor the observed effects.

Abstract

In this paper we present a theoretical analysis of the effect of magnetostriction on quantum oscillations of elastic constants in metals under strong magnetic fields. It is shown that at low temperatures a significant softening of some acoustic modes could occur near peaks of quantum oscillations of the electron density of states (DOS) at the Fermi surface (FS). This effect is caused by a magnetic instability of a special kind, and it can give rise to a lattice instability. We also show that the most favorable conditions for this instability to be revealed occur in metals whose Fermi surfaces include nearly cylindrical segments.