Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 85: Ultrafast Electron Dynamics at Surfaces and Interfaces II: New Methods and Developments

O 85.6: Vortrag

Donnerstag, 4. April 2019, 16:15–16:30, H16

Time resolved momentum microscopy on FeRh thin films, revealing ultrafast time scales for antiferro- to ferromagnetic phase transition. — •Steinn Ymir Agustsson¹, Federico Pressacco², Michael Heber³, Dmytro Kutnyakhov³, Dmitry Vasilyev¹, Jon Ander Arregi⁴, Vojtech Uhlir⁴, Guenter Brenner³, Davide Curcio⁵, Yves Acremann⁶, Fausto Sirotti⁷, Gerd Schoenhense¹, Hans-Joachim Elmers¹, Jure Demsar¹, and Wilfried Wurth^2,3 — ¹Institute of Physics, Uni. Mainz, Germany — ²CFEL, Hamburg, Germany — ³DESY, Hamburg, Germany — ⁴CEITEC BUT, Czech Republic — ⁵Aarhus University, Denmark — ⁶ETH Zurich, Switzerland — ⁷École Polytechnique, CNRS, France

The development of a momentum microscope for parallel electron detection, coupled to ultrafast extreme ultraviolet laser sources allows simultaneous observation of time, momentum and energy resolved photo-electrons excited by femtosecond laser pulses. In such experiments performed at the Free Electron Laser FLASH (DESY, Hamburg) we studied the electron redistribution upon laser induced phase transition between anti-ferromagnetic and ferromagnetic phases of FeRh. By optimizing the microscope and changing the settings of the electron optics, we could strongly reduce the effect of space charge with no loss of energy or time resolution. Such experimental conditions are the key to measuring the ultrafast response of excited carriers in complex quantum materials as well as in simple metals, where photo-excited electron-electron and electron-phonon thermalization dynamics are still not fully understood.