scholarly journals 1D charge density wave in the hidden order state of URu2Si2

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Edwin Herrera ◽  
Víctor Barrena ◽  
Isabel Guillamón ◽  
José Augusto Galvis ◽  
William J. Herrera ◽  
...  
Keyword(s):  
Charge Density ◽  
Single Crystals ◽  
Charge Density Wave ◽  
Density Wave ◽  
Scanning Tunneling ◽  
Temperature Phase ◽  
Tunneling Microscopy ◽  
Flat Surfaces ◽  
Fracture Dynamics ◽  
Hidden Order

AbstractSingle crystals of URu2Si2 show below 17.5 K a transition into an ordered state with a significantly reduced entropy. The low temperature phase is called the hidden order (HO) state, because its microscopic origin is still unknown—there are no charge, structural or magnetic transitions associated to HO. Here we report a one-dimensional (1D) charge modulation within the HO state of URu2Si2. We perform detailed Scanning Tunneling Microscopy (STM) experiments with high resolution on many atomically flat surfaces of URu2Si2 obtained by fracturing single crystals at cryogenic temperatures and find a 1D charge density wave with a large wavevector. We show that the 1D modulation is connected to the dynamical magnetic excitations of the HO through a moiré construction and appears as a consequence of excitations quenched through the interaction between the travelling fracture front and the dynamic modes of the crystal. The combination of fracture dynamics and the dynamics of the solid provides a method to create ground states and shows that charge interactions are among the most relevant features competing with HO in URu2Si2.

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.

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