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OFFPRINT Strain-induced semimetal-metal transition in silicene G. Liu, M. S. Wu, C. Y. Ouyang and B. Xu EPL, 99 (2012) 17010 Please visit the new website www.epljournal.org A LETTERS JOURNAL EXPLORING THE FRONTIERS OF PHYSICS AN INVITATION TO SUBMIT YOUR WORK www.epljournal.org The Editorial Board invites you to submit your letters to EPL EPL is a leading international journal publishing original, high-quality Letters in all areas of physics, ranging from condensed matter topics and interdisciplinary research to astrophysics, geophysics, plasma and fusion sciences, including those with application potential. The high profile of the journal combined with the excellent scientific quality of the articles continue to ensure EPL is an essential resource for its worldwide audience. EPL offers authors global visibility and a great opportunity to share their work with others across the whole of the physics community. 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Each compilation is led by its own Co-Editor, who is a leading scientist in that field, and who is responsible for overseeing the review process, selecting referees and making publication decisions for every manuscript. • Graphene Biaxial strain on lens-shaped quantum rings of different inner radii, adapted from Zhang et al 2008 EPL 83 67004. • Liquid Crystals • High Transition Temperature Superconductors • Quantum Information Processing & Communication • Biological & Soft Matter Physics • Atomic, Molecular & Optical Physics • Bose–Einstein Condensates & Ultracold Gases • Metamaterials, Nanostructures & Magnetic Materials • Mathematical Methods • Physics of Gases, Plasmas & Electric Fields Artistic impression of electrostatic particle–particle • High Energy Nuclear Physics interactions in dielectrophoresis, adapted from N Aubry and P Singh 2006 EPL 74 623. If you are working on research in any of these areas, the Co-Editors would be delighted to receive your submission. Articles should be submitted via the automated manuscript system at www.epletters.net If you would like further information about our author service or EPL in general, please visit www.epljournal.org or e-mail us at [email protected] Artistic impression of velocity and normal stress profiles around a sphere that moves through a polymer solution, adapted from R Tuinier, J K G Dhont and T-H Fan 2006 EPL 75 929. Image: Ornamental multiplication of space-time figures of temperature transformation rules (adapted from T. S. Bíró and P. Ván 2010 EPL 89 30001; artistic impression by Frédérique Swist). July 2012 EPL, 99 (2012) 17010 www.epljournal.org doi: 10.1209/0295-5075/99/17010 Strain-induced semimetal-metal transition in silicene G. Liu, M. S. Wu, C. Y. Ouyang and B. Xu(a) College of Physics and Communication Electronics, Jiangxi Normal University - Nanchang, Jiangxi, 330022, PRC received 16 April 2012; accepted in final form 19 June 2012 published online 11 July 2012 PACS 73.22.-f – Electronic structure of nanoscale materials and related systems PACS 71.15.Mb – Density functional theory, local density approximation, gradient and other corrections Abstract – The effect of the tensile strain on the electronic structure of the silicene is studied by using first-principles density functional theory. It is found that a semimetal-metal transition occurs when an in-plane strain larger than 7.5% is applied in silicene. The downward movement of the lowest conduction band at Γ-point, which originates from the weakened interaction between neighboring Si atoms, leads to the transition. The proposed mechanical control of the electronic properties will widen the application of the silicene in Si-based nanotechnology. Copyright c EPLA, 2012 Silicene, a two-dimensional (2D) monolayer honeycomb field [21]. If the semimetal-metal transition can be real- structure of silicon atoms, has recently attracted intensive ized, the potential applications of silicene will be wider in attention from the scientific community [1–12]. Compared the future nanotechnology. with graphene, the hottest 2D materials in the past several In this letter, we study the response of silicene under years, silicene could have more potential application in the the biaxial tensile strain. The transition from semimetal future Si-based nanotechnology, because they could enable to metal is predicted in silicene when the strain is beyond the electronics industry to produce fast nanoscale elec- 7.5%. Energy band structures reveal that the transition tronics without retooling to use carbon instead of silicon. results from the downward shift of the lowest conduction Experimentally, Nakano et al. reported the synthesis of band at Γ-point as increasing the strain. Further analysis silicene via the chemical exfoliation of CaSi2 [13]. Recently, of partial charge density shows that the downward shift of the possible growth of silicene nanoribbon on Ag (100) the lowest conduction band is related to the weakening of or Ag (110) substrates has been reported [14–17]. Since the π∗ bond due to the increase of the Si-Si bond length. silicon prefers sp3 hybridization instead of sp2, silicene All calculations were performed using the Vienna ab is energetically favorable as a low-buckled (LB) struc- initio simulation package (VASP) code, and adopting ture [18,19]. More interestingly, theoretical calculations the projector augmented-wave (PAW) potentials [22] on silicene show that the π and π∗ bands linearly cross and Perdew-Burke-Ernzerhof (PBE) generalized gradient at the Fermi level, reflecting the semimetallic or zero- approximation (GGA) exchange correlation functional gap semiconducting character of silicene [18,19]. Similar [23]. The energy cutoff for expansion of wave functions to graphene, therefore, it is important to modify a silicene and potentials is 550 eV. Monkhorst-Pack special k-point sheet in order to tailor its properties. For example, hydro- method [24] was used with a grid of 40 × 40 × 1. The genation of silicene can open a gap [3,7]. By using ab initio entire systems were relaxed by conjugate gradient method calculations, Ni et al. predicted that a vertical electric until the force on each atom is less than 0.001 eV/A.˚ The field is able to open a band gap in semimetallic single- 1 × 1 unit cell was employed in our calculations. We set layer buckled silicene [20]. They also found that the size up a vacuum region of 11.76 A˚ along the direction vertical of the band gap can be linearly tuned by the intensity of to the silicene layer to avoid the interaction between two the electric field. Though many efforts have been focused adjacent images. on the transition from semimetal to semiconductor for The relaxed structure of silicene is shown in fig. 1. The silicene, the study related to its change from semimetal optimized lattice parameter a is 3.86 A,˚ in agreement with to metal is not available in the literature except for the previous results (a =3.86 A)˚ [25]. The Si-Si bond length case subjected to a sufficiently high transverse electric is calculated to be 2.27 A,˚ showing a contraction of the bond compared with bulk Si. The buckling parameter Δ (a)E-mail: [email protected] (as shown in fig. 1(a)) is 0.46 A,˚ also consistent with other 17010-p1 G. Liu et al. without strain present the semimetallic character, with π and π∗ bands both crossing the Fermi level at the K-point, as shown in fig.
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