Using density functional theory calculations, we have systematically explored the effect of surface adsorption of different atoms on the electronic properties of monolayer molybdenum disulphide (MoS 2 ). We have chosen a few representative members from each group in the periodic table, ranging from alkali metals (group I) to halogens (group VII) and calculated the electronic band structure of the adatom-MoS 2 system for the most energetically stable location of the adatom adsorbed on MoS 2 . Calculated value of charge transfer from the adsorbed adatom to MoS 2 and resultant shifting of the Fermi level to the conduction band suggests that the group I (Li, Na, K) and group II metals (Mg, Ca) are the most effective adatoms to enhance the n-type mobile carrier density in MoS 2 . Our calculation is in good agreement with the experimental observation for K [Nano Lett. 13, 1991].

Two dimensional magnetic materials, with tunable electronic properties could lead to new spintronic, magnetic and magneto-optic applications. Here, we explore intrinsic magnetic ordering in two dimensional monolayers of transition metal tri-halides (MX 3 , M = V, Cr, Mn, Fe and Ni, and X = F, Cl, Br and I), using density functional theory. We find that other than FeX 3 family which has an anti-ferromagnetic ground state, rest of the trihalides are ferromagnetic. Amongst these the VX 3 and NiX 3 family are found to have the highest magnetic transition temperature, beyond the room temperature. In terms of electronic properties, the tri-halides of Mn and Ni are either half metals or Dirac half metals, while the tri-halides of V, Fe and Cr are insulators. Among all the trihalides studied in this paper, we find the existence of very clean spin polarized Dirac half metallic state in MnF 3 , MnCl 3 , MnBr 3 , NiF 3 and NiCl 3 . These spin polarized Dirac half metals will be immensely useful for spin-current generation and other spintronic applications. arXiv:1905.13677v1 [cond-mat.mtrl-sci]

We study the effect of surface adsorption of 27 different adatoms on the electronic and magnetic properties of monolayer black phosphorus using density functional theory. Choosing a few representative elements from each group, ranging from alkali metals (group I) to halogens (group VII), we calculate the band structure, density of states, magnetic moment and effective mass for the energetically most stable location of the adatom on monolayer phosphorene. We predict that group I metals (Li, Na, K), and group III adatoms (Al, Ga, In) are effective in enhancing the n-type mobile carrier density, with group III adatoms resulting in lower effective mass of the electrons, and thus higher mobilities. Furthermore we find that the adatoms of transition metals Ti and Fe, produce a finite magnetic moment (1.87 and 2.31 µB) in monolayer phosphorene, with different band gap and electronic effective masses (and thus mobilities), which approximately differ by a factor of 10 for spin up and spin down electrons opening up the possibility for exploring spintronic applications. arXiv:1503.04296v2 [cond-mat.mes-hall]

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We explore the impact of a vertical electric field on the electronic properties of rippled monolayer blue phosphorus (blue-P). On the basis of density functional theory calculations, we demonstrate electric field-induced splitting and shifting of the energy levels of rippled blue-P, similar to the Stark effect in atomic energy levels. The band gap of rippled blue-P is found to decrease linearly either with increasing electric field strength for a fixed ripple height or with increasing ripple height for a fixed electric field strength. The application of a transverse electric field also leads to a spatial separation of the conduction and valence band states near the bottom and the top of the ripple, respectively. The demonstrated Stark effect in rippled blue-P offers a potent band gap engineering tool, and it may open a gateway for possible electronic and optoelectronic applications.