Abstract
The electrocaloric (EC) effect is the change in temperature and entropy of a material driven by the application of an electric field. Our tight-binding calculations linked to Fermi statistics, show that the EC effect can be produced in trilayer graphene (TLG) structures connected to a heat source, triggered by changes in the electronic density of states (DOS) at the Fermi level when external gate fields are applied on the outer graphene layers. We demonstrate that entropy changes are sensitive to the stacking arrangement in TLG systems. The AAA-stacked TLG presents an inverse EC response (cooling) regardless of the temperature value and gate field potential strength, whereas the EC effect in ABC-stacked TLG remains direct (heating) above room temperature. We reveal otherwise the TLG with Bernal-ABA stacking generates both the direct and inverse EC response within the same sample, associated with gate-dependent electronic transitions of thermally excited charge carriers from the valence band to the conduction band in the band structure. The novel charge carrier electrocaloric effect we propose in quantum layered systems may bring a wide variety of prototype van der Waals materials that could be used as versatile platforms to controlling the thermal response in nanodevices.
Highlights
The electrocaloric (EC) effect is the change in temperature and entropy of a material driven by the application of an electric field
Through the novel EC phenomenon due to charge carriers in van der Waals (vdW) systems we propose here, we are joining the physics of quantum layered 2D materials—using the electronic band structure and density of states (DOS)—with thermodynamics, so that the electronic entropy plays a fundamental role, which we demonstrate its fully dependent on the stacking arrangement of each trilayer graphene (TLG) because of its distinctive topology
Through Bloch electrons in parameterized tight-binding (TB) models linked to Fermi statistics, we show how the thermal response varies within each TLG stacking as a result of the quantum-thermodynamic processes involved at low energies
Summary
The electrocaloric (EC) effect is the change in temperature and entropy of a material driven by the application of an electric field. We reveal otherwise the TLG with Bernal-ABA stacking generates both the direct and inverse EC response within the same sample, associated with gate-dependent electronic transitions of thermally excited charge carriers from the valence band to the conduction band in the band structure. The novel charge carrier electrocaloric effect we propose in quantum layered systems may bring a wide variety of prototype van der Waals materials that could be used as versatile platforms to controlling the thermal response in nanodevices. The EC effect—the change in temperature and entropy as an electric field is applied—has been widely studied in three-dimensional dielectric multilayer capacitors (MLC) by considering a different number of layers with diverse thicknesses in the samples, typically of the order of micrometers[7,8], and finding thickness-dependent thermal r esponses[8]. Graphene multilayers can experimentally be obtained with different stacking orders
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