Non-Lifshitz-Kosevich field-and temperature-dependent amplitude of quantum oscillations in the quasi-two dimensional metal $\theta$-(ET) 4 ZnBr 4 (C 6 H 4 Cl 2 )

TL;DR

This study investigates quantum oscillations in a quasi-two-dimensional metal, revealing deviations from traditional models due to second order effects, especially in forbidden orbits and harmonic components.

Contribution

It introduces an analytic approach including second order damping terms to explain non-Lifshitz-Kosevich behavior in quantum oscillation amplitudes.

Findings

Second order terms explain forbidden orbit amplitudes.

Deviations from Lifshitz-Kosevich formula observed.

Significant influence on harmonic and combination frequencies.

Abstract

According to band structure calculations, the Fermi surface of the quasi-two dimensional metal $\theta$-(ET) 4 ZnBr 4 (C 6 H 4 Cl 2) illustrates the linear chain of coupled orbits model. Accordingly, de Haas-van Alphen oscillations spectra recorded in pulsed magnetic field of up to 55 T evidence many Fourier components, the frequency of which are linear combinations of the frequencies relevant to the closed $\alpha$ and the magnetic breakdown $\beta$ orbits. The field and temperature dependence of these component's amplitude are quantitatively accounted for by analytic calculations including, beyond the Lifshitz-Kosevich formula, second order terms in damping factors due to the oscillation of the chemical potential as the magnetic field varies. Whereas these second order terms are negligible for the orbits $\alpha$, $\beta$ and 2$\beta$ -- $\alpha$, they are solely responsible for the 'forbidden orbit' $\beta$ -- $\alpha$ and its harmonic and have a significant influence on Fourier components such as 2$\alpha$ and $\beta$ + $\alpha$, yielding strongly non-Lifshitz-Kosevich behaviour in the latter case.