1T-TaS2 charge density wave under the microscope of MeV ultrafast electron diffraction

Date

Feb 23, 2017

Time

1:30 PM - 2:30 PM

Speaker

Dr. Loic Le Guyader

Affiliation

Spectroscopy & Coherent Scattering European XFEL GmbH

Language

en

Main Topic

Materialien

Other Topics

Materialien, Physik

Host

Description

Abstract Recent developments in the control of charge density wave (CDW), i.e. a combined periodic modulation of the electron density and a periodic lattice distortion, with either current or fs laser pulses could open the door for novel electronic devices. [1-4] The 1T polytype of TaS2 displays a rich phase diagram, with metallic phases characterized by various degrees of commensurability above 180 K and an insulating commensurate CDW phase below. Fs laser excitation can induce a metallic metastable hidden phase. [3,4] While CDW systems are essentially thought of as 2-dimensional systems, it is speculated that the insulating and conducting phase properties are driven by the layer stacking order in the 3rd dimension. [5] How and on which time scale does the stacking order evolves upon femtosecond laser excitation? Using the 3 MeV electron diffraction setup at SLAC, [6] we investigated the ultrafast dynamics of the commensurate to incommensurate phase transition upon excitation by a femtosecond 800 nm wavelength laser pulse. Taking advantage of the nearly flat Ewald sphere displayed by 3 MeV electrons, we measured simultaneously a complete set of CDW satellites reflections, evidencing an unexpected different behavior between the layer stacking order and partial disorder.

Links

• Seminars at the IFW

Last modified: Feb 23, 2017, 8:49:42 AM