Electric field-induced suppression of orbital-resolved electronic thermal conductivity in monolayer honeycomb borophene oxide (h-B2O)

Abstract

In the expanding landscape of two-dimensional (2D) materials, the investigation of systems beyond graphene is considered essential for the advancement of next-generation electronic and thermoelectric technologies. Monolayer honeycomb borophene oxide (h-B2O), a boron-based 2D material, has been identified as a promising candidate due to its unique topological features, such as nodal loops, and its potential superconducting behavior. In this study, the electronic properties of monolayer h-B2O are theoretically examined. Its band structure (BS) and density of states (DOS) are analyzed, revealing a metallic nature. To gain further insight, a tight-binding (TB) Hamiltonian is constructed incorporating the Py and Pz orbitals of boron, capturing the essential physics underlying the material’s low-energy electronic behavior. For the first time, the electronic thermal conductivity (ETC) of monolayer h-B2O is calculated using the Kubo-Greenwood formalism within the diffusive transport regime, under both pristine and electrostatically gated conditions. The results reveal pronounced anisotropy (κyy ≫ κxx), with room-temperature ETC values of 5.9 × 10−2 mW.m−1.K−1, 1 mW.m−1.K−1, and 0.17 mW.m−1.K−1 along the armchair (κxx), zigzag (κyy), and anomalous Righi-Leduc effect (κxy) directions, respectively. Furthermore, charge transport is found to be predominantly governed by the Pz orbital of boron, owing to its higher carrier occupancy compared to the Py orbital. The effect of a perpendicular electric field (PEF) with varying strengths (V = 0.5, 0.75, and 1 eV) is also investigated. The applied field induces bandgap openings at the Dirac cones located along the X–Γ path, with the gap magnitude following the relation Eg = 2V, and causes noticeable shifts in the Van Hove singularities in the DOS. As the field strength increases, the ETC in all directions exhibits a consistent decreasing trend, with approximately equal relative reductions. These results underscore the tunability of ETC in h-B2O, highlighting its potential for advanced thermal management applications, including thermal cloaking.