Abstract
Graphene, despite its many unique properties, is neither intrinsically polar due to inversion symmetry nor magnetic. However, based on density functional theory, we find that Mn, one of transition metals, embedded in single or double vacancy (Mn@SV and Mn@DV) in a graphene monolayer induces a dipole moment perpendicular to the sheet, which can be switched from up to down by Mn penetration through the graphene. Such switching could be realized by an external stimuli introduced through the tip of a scanning probe microscope, as already utilized in the studies of molecular switches. We estimate the energy barriers for dipole switching, which are found to be 2.60 eV and 0.28 eV for Mn@SV and Mn@DV, respectively. However, by applying biaxial tensile strain, we propose a mechanism for tuning the barrier. We find that 10% biaxial tensile strain, which is already experimentally achievable in graphene-like two-dimensional materials, can significantly reduce the barrier to 0.16 eV in Mn@SV. Moreover, in agreement with previous studies, we find a high magnetic moment of 3 μB for both Mn@SV and Mn@DV, promising the potential of these structures in spintronics as well as in nanoscale electro-mechanical or memory devices.
Highlights
Graphene—one atomic layer of C atoms arranged in a hexagonal lattice with many unique and extraordinary properties—has been an object of intense research activities that might revolutionize generation nano scale devices[1,2,3]
Experimental observation of piezoelectricity in MoS2 membranes with the odd number of layers has already been reported for nano-electro-mechanical systems (NEMS)[14,15]
A considerable body of theoretical as well as experimental works has been devoted on an isolated transition metal (TM) atom in a graphene sheet, which is considered as an ideal situation because of non-magnetic graphene[17,18,19,21]
Summary
Despite its many unique properties, is neither intrinsically polar due to inversion symmetry nor magnetic. We show that 10% biaxial tensile strain, which could be experimentally achievable for graphene like 2D materials[28,29], can significantly reduce the barrier indicating a way to switch the dipole moment as such structures are already experimentally available[17]. We emphasize that such dipole switching could be considered as analogous to the molecular switching[16] where a molecular state can be switched from one to another under an external stimuli usually
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