Unveiling the double-peak structure of quantum oscillations in the specific heat

TL;DR

This paper reveals a double-peak structure in quantum oscillations of specific heat in graphite, challenging traditional single-peak expectations and offering a new spectroscopic tool for probing electronic states and properties.

Contribution

It demonstrates the existence of a double-peak structure in quantum oscillations of specific heat, predicted by free electron theory, and proposes its use for precise determination of the Lande g-factor.

Findings

Double-peak structure observed in quantum oscillations of specific heat.

The double-peak is predicted by the kernel term in free electron theory.

The structure can be used to accurately determine the Lande g-factor.

Abstract

Quantum oscillation phenomenon is an essential tool to understand the electronic structure of quantum matter. Here we report a systematic study of quantum oscillations in the electronic specific heat $C_{el}$ in natural graphite. We show that the crossing of a single spin Landau level and the Fermi energy give rise to a double-peak structure, in striking contrast to the single peak expected from Lifshitz-Kosevich theory. Intriguingly, the double-peak structure is predicted by the kernel term for $C_{el}/T$ in the free electron theory. The $C_{el}/T$ represents a spectroscopic tuning fork of width 4.8 $k_B T$ which can be tuned at will to resonance. Using a coincidence method, the double-peak structure can be used to accurately determine the Lande $g$-factor of quantum materials. More generally, the tuning fork can be used to reveal any peak in fermionic density of states tuned by magnetic field, such as Lifshitz transition in heavy-fermion compounds.