Direction-Dependent Quantum Transport Properties of MoS$_2$ Integrated into Biphenylene Configuration

Abstract: Motivated by the experimental realization of the two-dimensional (2D) carbon biphenylene network (BPN), the theoretical extension of the BPN topology to various groups of elements was successfully implemented. In this work, we conducted first principles and quantum transport calculations to reveal the electronic, thermal, thermoelectric performance and current-voltage (\textit{I-V}) behavior of the pristine MoS$2$-BPN by using density functional theory (DFT) combined with Non-Equilibrium Green's Function (NEGF) formalism. At room temperature, the phonon thermal conductance is remarkably low along both the armchair and zigzag orientations, with values of 0.28 nW/K and 0.23 nW/K, respectively. The directional dependence of the electronic and thermal transport properties is clearly reflected in the thermoelectric figure of merit ($zT$) values, which reach first peaks at 0.27 and 0.19 along the armchair and zigzag directions, respectively. The current-voltage ($I-V$) characteristics demonstrate an exceptionally strong transport anisotropy, characterized by a substantial current ratio of $I{\text{armchair}}/I_{\text{zigzag}} \approx 7 \times 10^4$. Furthermore, while the current along the armchair direction increases steadily with the applied bias, transport along the zigzag direction is characterized by a pronounced intrinsic negative differential conductance (NDC). This contrast highlights fundamentally distinct charge transport mechanisms along the two orthogonal axes. Consequently, different directions of this BPN phase of MoS$_2$ can be tailored for distinct nanoelectronic applications, where the armchair and zigzag axes serve as a reliable current switch and an active NDC device, respectively.