Feb 2, 2018–Feb 2, 2018
from 11:00am–12:00pm
Seminar: THz Spintronics in Magnetic Heterostructures: The Role of Interfaces
The Center for Memory and Recording Research is hosting Guanqiao Li to speak on the topic of “THz Spintronics in Magnetic Heterostructures: The Role of Interfaces”.
11:00 AM Lecture
12:00 PM Pizza Lunch
Abstract: THz spectroscopy provides a convenient way to directly probe the dynamics of photocurrents and spins on the picosecond and sub-picosecond timescale. Recently it was shown that circularly polarized femtosecond laser excitation in a Co/Pt bilayer can effectively generate an ultrafast photocurrent pulse at the interface [1]. The direction of this photocurrent is parallel to the in-plane magnetization of the Co layer and can be controlled by both the magnetic polarity of Co and the chirality of the circularly polarized light. Simultaneously, an ultrafast spin current pulse is generated in the Co layer, which is converted to a charge current in the Pt layer via the inverse Spin-Hall effect [2]. This charge current is in-plane and perpendicular to the magnetization of Co. Moreover, its direction can be controlled by the net spin orientation of the ultrafast spin current by switching the magnetization orientation of Co. A convenient way to probe these ultrafast phenomena is to employ THz time-domain emission spectroscopy. The basic principle of this method is that the (sub)picosecond currents will generate electric radiation in the THz frequency that can be probed via a technique called electro-optical sampling. Since the polarization of THz radiation generated by the two charge currents are perpendicular with respect to each other, one can study each phenomenon separately using wire-grid polarizers. The role of the interfaces between magnetic and non-magnetic layers will be discussed, in particular the generation of the ultrafast photocurrents in Co/ZnO/Pt, Co/Cu/Pt trilayers. The separation of the Co/Pt interface with interlayers of different characteristics is shown to give a better understanding of the role of the interface on the generation of ultrafast photocurrents.
References: [1] Huisman, T. J., et al. “Femtosecond control of electric currents in metallic ferromagnetic heterostructures.” Nature nanotechnology (2016).
[2] Kampfrath, T., et al. “Terahertz spin current pulses controlled by magnetic heterostructures”, Nature nanotechnology (2013).
Biography: Guanqiao Li was born in Beijing (China) on August 31, 1989. He came to the Netherlands at the age of 3. He obtained his master’s degree Experimental Physics (graduated in 2016) from Utrecht University (the
Netherlands). Currently, he is a PhD student in Prof. Alexey Kimel’s group at Radboud University Nijmegen (the Netherlands). His research focuses on exploring the field of THz spintronics and (sub)picosecond photocurrent phenomena. Specializing in THz spectroscopy, and ultrafast photocurrents and spintronics in magnetic heterostructures.
Event Website
Date and Time
Feb 2, 2018–Feb 2, 2018
from 11:00am–12:00pm
Location
Jack Keil Wolf Auditorium, Center for Memory and Recording Research (CMRR)
Event Registration
Registration is not required for this event.
Event Fee
Free
Contact
Iris Villanueva • ivilla@ucsd.edu • 8585346196
Audience
Faculty, Staff, Students, The General Public
Event Host
Eric Fullerton
Event Category
Talks and Lectures