High Coherence Electron Pulses for Ultrafast Transmission Electron Microscopy

TYPE	Special Seminar - Solid State Institute, Technion
Speaker:	Dr. Armin Feist
Affiliation:	IV. Physical Institute – Solids and Nanostructures, University of Göttingen, Göttingen, Germany
Date:	12.12.2019
Time:	10:00 - 11:00
Location:	Solid State Auditorium(Entrance)
Remark:	Host: Dr. Ido Kaminer
Presentation:

Abstract:

Ultrafast transmission electron microscopy (UTEM) combines the versatile nanoscale imaging, diffraction and spectroscopy available in electron microscopes with femtosecond temporal resolution achieved by a laser-pump/electron-probe scheme [1]. However, to make full use of the capabilities of state-of-the-art TEM, highly coherent electron pulses are required, demanding for novel photocathode concepts.

Here, I will describe the implementation of an advanced UTEM instrument utilizing laser-triggered field emitters and present first applications harnessing its superior electron beam coherence.

Specifically, the Göttingen UTEM employs electron pulses of excellent spatio-temporal properties (down to 0.8-nm focal spot size, 200-fs pulse duration and 0.6-eV spectral bandwidth), generated by localized linear photoemission from a Schottky-type field emitter tip [2].

I will give a brief overview of current experiments in ultrafast imaging and local diffractive probing of condensed matter systems. These include the local diffractive probing of strain dynamics in a single crystalline graphite membrane [3], the laser-induced dynamics of nanopatterned magnetic permalloy thin films [4], and the time-resolved mapping of the charge-density wave phase transition in the correlated material 1T-TaS₂.

In a further line of applications, we utilize the interaction of fast electrons with intense optical near-fields to establish quantum coherent control of free electron pulses by light [5]. As a particular example, I will describe the three-dimensional optical phase-shaping of electron beams, with applications for generating atto second electron pulse trains [6] and coherent electron beam splitters.

Reference:

[1] A.H. Zewail, Science 328, 187 (2010).
[2] A. Feist et al., Ultramicroscopy 176, 63 (2017).
[3] A. Feist et al., Struct. Dyn. 5, 14302 (2018).
[4] N. Rubiano da Silva et al., Phys. Rev. X 8, 031052 (2018).
[5] A. Feist et al., Nature 521, 200–203 (2015).
[6] K.E. Priebe et al., Nat. Photonics 11, 793–797 (2017).