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Spontaneous Symmetry Breaking and Dynamic Phase Transition in Monolayer Silicene

2013; American Physical Society; Volume: 110; Issue: 8 Linguagem: Inglês

10.1103/physrevlett.110.085504

1092-0145

Lan Chen, Hui Li, Baojie Feng, Zijing Ding, Jinglan Qiu, Peng Cheng, Kehui Wu, Sheng Meng,

Molecular Junctions and Nanostructures

The (sqrt[3]×sqrt[3])R30° honeycomb of silicene monolayer on Ag(111) was found to undergo a phase transition to two types of mirror-symmetric boundary-separated rhombic phases at temperatures below 40 K by scanning tunneling microscopy. The first-principles calculations reveal that weak interactions between silicene and Ag(111) drive the spontaneous unusual buckling in the monolayer silicene, forming two energy-degenerate and mirror-symmetric (sqrt[3]×sqrt[3])R30° rhombic phases, in which the linear band dispersion near the Dirac point and a significant gap opening (150 meV) at the Dirac point were induced. The low transition barrier between these two phases enables them to be interchangeable through dynamic flip-flop motion, resulting in the (sqrt[3]×sqrt[3])R30° honeycomb structure observed at high temperature.