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Paper   IPM / P / 17145
School of Physics
  Title:   Symmetry breaking induced bandgap opening in epitaxial germanene on WSe$_2$
1.  Q. Wu
2.  M. Bagheri Tagani
3.  Q. Tian
4.  S. Izadi Vishkayi
5.  L. Zhang
6.  L. Jing Yin
7.  Y. Tian
8.  L. Zhang
9.  Zh. Qin
  Status:   Published
  Journal: Appl.Phys.Lett
  Vol.:  121
  Year:  2023
  Pages:   051901
  Supported by:  IPM
Germanene has attracted much attention because the material was predicted to host Dirac fermions. However, the synthesis of germanene is still in its infancy; moreover, the predicted tiny bandgap induced by the spinâ??orbit coupling is far from practical applications for nanoelectronic devices. Herein, quasi-freestanding germanene with linear dispersion relation of the band structure is well grown on a WSe$_2$/Au(100) substrate. Band structure calculations reveal that the interaction of germanene with the substrate destroys the sublattice symmetry. The energy-dependent contribution of $\sigma$ orbitals responsible for band crossing at the Fermi level around the $\Gamma$ point induces asymmetric density of states at the Dirac point. Upon annealing in ultra-high vacuum, we observe a bandgap opening in germanene of about $\sim$0.17 eV, which is attributed to a sublattice symmetry breaking in germanene and the emergence of a net electric field. This work provides an effective method to tune or tailor the electronic properties of germanene, paving the way to germanene-based field-effect applications.

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