Impurity-engineered orbital contributions to the electronic heat capacity of highly stable monolayer h-B2O.

Abstract

Monolayer honeycomb borophene oxide (h-B2O) combines exceptional thermodynamic stability with nontrivial topology and prospective superconductivity, yet its thermodynamic behavior remains largely unexplored. Here, we construct an orbital-resolved tight-binding (TB) model based on the boron py and pz orbitals and, through detailed analysis of the corresponding band structure (BS) and density of states (DOS), establish the metallic character of h-B2O. We further determine, for the first time, its electronic heat capacity (EHC). At 300 K, the orbital components are and , with , reflecting the enhanced pz-orbital DOS near the Fermi level. In the pristine limit, the low-temperature EHC exhibits a linear dependence below ≈25 K, consistent with the Sommerfeld model (Ce = γT), and shows a Schottky anomaly near 75 K. To assess the robustness of the EHC against disorder, we treat impurity scattering within the T-matrix formalism and calculate the corresponding self-energies for both n-type (u = +10 eV) and p-type (u = -10 eV) dopants over ni = 0-10% at 300 K. The EHC does not follow a universal monotonic trend but instead exhibits pronounced orbital-selective modulation. For n-type doping, the total EHC closely follows the py channel, reaching a maximum increase of +13.1% at ni = 1% and a minimum decrease of 26.2% at ni = 9%. Under p-type doping, the response is dominated by the pz orbital, increasing by +55.7% at ni = 9% and decreasing by 26.4% at ni = 10%. These results establish h-B2O as a model system for investigating orbital-selective modifications of electronic thermodynamic properties induced by charged impurities. The calculated Cv provides a sensitive orbital-resolved thermodynamic descriptor that can support future studies of impurity effects and coupled thermal or electronic phenomena in two-dimensional boron-based materials.