Gate-tunable direct and inverse electrocaloric effect in trilayer graphene

TL;DR

This study demonstrates how the electrocaloric effect in trilayer graphene varies with stacking order and gate voltage, revealing potential for nanoscale thermal management in electronic devices.

Contribution

It provides a detailed theoretical analysis of the stacking-dependent electrocaloric response in trilayer graphene, highlighting the ability to switch between direct and inverse effects via gate tuning.

Findings

AAA-stacked TLG exhibits inverse EC response (cooling).

ABC-stacked TLG shows a consistent direct EC response (heating).

Bernal-ABA stacking generates both EC responses depending on conditions.

Abstract

The electrocaloric (EC) effect is the reversible change in temperature and/or entropy of a material when it is subjected to an adiabatic electric field change. Our tight-binding calculations linked to Fermi statistics, show that the EC effect is sensitive to the stacking arrangement in trilayer graphene (TLG) structures connected to a heat source, and is produced by changes of the electronic density of states (DOS) near the Fermi level when external gate fields are applied on the outer graphene layers. We demonstrate the AAA-stacked TLG presents an inverse EC response (cooling), whereas the EC effect in ABC-stacked TLG remains direct (heating) regardless of the applied gate field potential strength. We reveal otherwise the TLG with Bernal-ABA stacking geometry generates both the inverse and direct EC response in the same sample, associated with a gate-dependent electronic entropy transition at finite temperature. By varying the chemical potential to different Fermi levels, we find maxima and minima of the DOS are located near the extremes of the electronic entropy, which are correlated with sign changes in the differential entropy per particle, giving a particular experimentally measurable electronic entropy spectrum for each TLG geometry. The EC effect in quantum two-dimensional layered systems may bring a wide variety of prototype van der Waals materials that could be used as versatile platforms to controlling the temperature in nanoscale electronic devices required in modern portable on-chip technologies.