Field-Induced Metallization and enhanced thermodynamic responses in bilayer γ-graphyne: Effects of Stacking Configuration

In this work, a comprehensive theoretical framework has been developed to clarify how external perturbations and stacking geometry collectively determine the electronic, thermodynamic and thermoelectric properties of bilayer γ‑graphyne. Within a tight-binding Hamiltonian combined with the Kubo–Greenwood formalism, the evolution of the density of states (DOS) and transport coefficients is systematically explored for both AA and AB stacking configurations under the combined influence of a perpendicular bias voltage and a Zeeman-type spin-splitting field. The results demonstrate a pronounced stacking-dependent electronic response: the AA configuration retains its intrinsic metallic character under all external conditions, whereas the AB configuration exhibits a tunable semiconducting behavior, characterized by substantial DOS reconstruction under bias voltage and a Zeeman-induced band gap closure. External perturbations significantly modify the DOS near the Fermi level, leading to notable changes in the temperature dependence of key thermodynamic and transport quantities, including heat capacity, magnetic susceptibility and electrical and thermal conductivities. Distinct thermodynamic responses emerge depending on the stacking geometry, with AA exhibiting a linear metallic behavior, in contrast to the nonlinear and highly tunable response of the AB configuration. The magnetic field is found to be more effective than bias voltage in enhancing thermoelectric performance in the AB stacking, primarily due to its role in gap suppression and carrier excitations. The thermoelectric figure of merit (ZT) exhibits a nontrivial dependence on temperature and external fields, with superior performance achieved in the AB configuration compared to AA under optimized conditions. These findings highlight bilayer γ-graphyne as a highly tunable platform for thermoelectric applications, where the interplay between stacking configuration, interlayer bias, and Zeeman-type spin splitting provides an effective route for controlling the low-energy electronic structure and the associated transport properties.