As the Fermi level and band structure of two-dimensional materials are readily tunable, they constitute an ideal platform for exploring the Lifshitz transition, a change in the topology of a material's Fermi surface. Using tetralayer graphene that host two intersecting massive Dirac bands, we demonstrate multiple Lifshitz transitions and multiband transport, which manifest as a nonmonotonic dependence of conductivity on the charge density n and out-of-plane electric field D, anomalous quantum Hall sequences and Landau level crossings that evolve with n, D, and B.

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Rotational spectra and temperature evaluation of C 2 molecules produced by pulsed laser irradiation to a graphite-water interface

Interlayer misorientation in transition metal dichalcogenides alters the interlayer distance, the electronic bandstructure, and the vibrational modes, but, its effect on the interlayer resistance is not known. This work analyzes the coherent interlayer resistance of misoriented 2H-MoS2 for low energy electrons and holes as a function of the misorientation angle. The electronic interlayer resistance monotonically increases with the supercell lattice constant by several orders of magnitude similar to that of misoriented bilayer graphene. The large hole coupling gives low interlayer hole resistance that weakly depends on the misorientation angle. Interlayer rotation between an n-type region and a p-type region will suppress the electron current with little effect on the hole current. We estimate numerical bounds and explain the results in terms of the orbital composition of the bands at high symmetry points. Density functional theory calculations provide the interlayer coupling used in both a tunneling Hamiltonian and a non-equilibrium Green function calculation of the resistivity.Introduction: There is tremondous interest in multilayer and heterostructure stacks of transition metal dichalcogenides (TMDs) . They exhibit strong spin orbit coupling and non-trivial topology [3][4][5] [14,17,20], and rectifying pn junctions [7,14,20]. Multilayer and heterostructure growth with stacking control have been demonstrated [20][21][22][23]. Recent reviews provide an overview of the state of the art [24,[27][28][29].For TMD misoriented bilayers, both experiments and simulations show that the interlayer coupling and the interlayer distance are sensitive to the rotation angle, and that the sensitivity of the coupling is very different for different valleys [11-13, 16, 25]. A small rotation angle in hetero-bilayers alters the inter-layer exciton dynamics [30,31]. While the effects of misorientation on the geometry, electronic bandstructure, and vibrational modes of bilayer TMDs have received significant attention, the effect of misorientation on the interlayer resistivity of TMDs has not yet been studied. Recent work considered the effect of misorientation on the in-plane transport [32]. In this work, we theoretically determine the coherent electron and hole interlayer (vertical) conductance of a misoriented MoS 2 interface as illustrated in Fig. 1(a).In MoS 2 bilayers, the low-energy electron transport takes place at the K valley, and the low-energy hole transport takes place at the Γ valley. This results in an extremely asymmetric response of the electron and