Observation of Multiple Charge Density Wave Phases in Epitaxial Monolayer 1T-VSe2 Film

2021 ◽  
Author(s):  
Junyu Zong ◽  
Yang Xie ◽  
Qinghao Meng ◽  
Qichao Tian ◽  
Wang Chen ◽  
...  
Keyword(s):  
Charge Density ◽  
Charge Density Wave ◽  
Density Wave ◽  
Deep Understanding ◽  
Spatial Modulation ◽  
Scanning Tunneling ◽  
Momentum Dependence ◽  
Significant Information ◽  
Step Transition ◽  
Gap Structure

Abstract As a special order of electronic correlation induced by spatial modulation, the charge density wave (CDW) phenomena in condensed matters attract enormous research interests. Here, using scanning-tunneling microscopy in various temperatures, we observe a new (2×1) CDW phase besides the (√7×√3) CDW phase in epitaxial monolayer 1T-VSe2 film. Combining the variable-temperature angle-resolved photoemission spectroscopic (ARPES) measurements, we discover an anisotropic CDW gap and a two-step transition associated with the different CDW phases, which were observed below 135 K for the (√7×√3) CDW phase and between 135 K to 330 K for the (2×1) CDW phase respectively. The (√7×√3) CDW phase results a full gap, while the (2×1) CDW phase shows highly momentum dependence and results a partial gap structure at the Fermi surface. This two-step transition with anisotropic gap opening and the resulted evolution in ARPES spectra are corroborated by our theoretical calculation based on a phenomenological form for the self-energy containing a two-gap structure. Our findings provide significant information and deep understanding on the CDW phases in monolayer 1T-VSe2 film as a 2D material.

scholarly journals A full gap above the Fermi level: the charge density wave of monolayer VS2

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Camiel van Efferen ◽  
Jan Berges ◽  
Joshua Hall ◽  
Erik van Loon ◽  
Stefan Kraus ◽  
...  
Keyword(s):  
Standard Model ◽  
Fermi Level ◽  
Charge Density ◽  
Charge Density Wave ◽  
Magnetic Circular Dichroism ◽  
Density Wave ◽  
Electronic Energy ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Metal Metal

AbstractIn the standard model of charge density wave (CDW) transitions, the displacement along a single phonon mode lowers the total electronic energy by creating a gap at the Fermi level, making the CDW a metal–insulator transition. Here, using scanning tunneling microscopy and spectroscopy and ab initio calculations, we show that VS2 realizes a CDW which stands out of this standard model. There is a full CDW gap residing in the unoccupied states of monolayer VS2. At the Fermi level, the CDW induces a topological metal-metal (Lifshitz) transition. Non-linear coupling of transverse and longitudinal phonons is essential for the formation of the CDW and the full gap above the Fermi level. Additionally, x-ray magnetic circular dichroism reveals the absence of net magnetization in this phase, pointing to coexisting charge and spin density waves in the ground state.

scholarly journals Unique Gap Structure and Symmetry of the Charge Density Wave in Single-Layer VSe2

2018 ◽  
Vol 121 (19) ◽  
Author(s):  
P. Chen ◽  
Woei Wu Pai ◽  
Y.-H. Chan ◽  
V. Madhavan ◽  
M. Y. Chou ◽  
...  
Keyword(s):  
Charge Density ◽  
Charge Density Wave ◽  
Density Wave ◽  
Single Layer ◽  
Gap Structure
Sign in / Sign up

Export Citation Format

Share Document