University of Minnesota
School of Physics & Astronomy
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Justin Watts

AMUNDH 40 (office), 612-625-1018
watts @ physics.umn.edu

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Summary of Interests
Experimental Condensed Matter Physics [Research Web Page]

About My Work

My current research in the Crowell and Leighton groups is focused on understanding spin transport in nanoscopic metallic devices. Using a device known as a nonlocal spin valve (NLSV) we are able to separate the electron's charge and spin degrees of freedom to generate a pure spin current that is not accompanied by a charge current. These devices allow us to probe the most fundamental aspects of spin transport without the need to decouple charge-based effects from our measurements. By studying both the materials properties of the metals used in the devices and the interactions of those materials with pure spin currents we can improve our understanding of the mechanisms responsible for the decay of spin polarization in non-magnetic metals and in doing so we can improve the outlook of applications utilizing spintronic devices.

My past work in the Crowell Group was focused on investigating the magnetic properties and spin dynamics of various magnetic materials such as Heusler alloys. This work is accomplished with the help of optical tools such as a near-infrared Titanium:Sapphire laser in a time-domain setup with the ability to measure the Magneto-Optic Kerr Effect (MOKE) of the material under study.

This type of setup is known as Time Resolved Kerr Microscopy and functions by measuring the change in polarization of the laser's probe beam after reflection from the sample. This rotation in the probe beam is caused by electron spin polarization in the material which we can excite by using a microwave frequency pump to generate magnetic fields which will cause a precession of the sample's magnetization and thus a precession of the polarization of the reflected probe beam. By directing the probe beam along a time-delay optical line we gain the ability to resolve the dynamics of the sample's magnetic response on picosecond (10^-12) time scales.

Clean room fabrication is often required to produce our own magnetic and electronic material samples with sub-micron (10^-6 meters) features capable of creating interesting phenomenon. These samples contain significant potential for applications in future spintronic devices.

Selected Publications

B. L. Le, J. Park, J. Sklenar, G.-W. Chern, C. Nisoli, J. D. Watts, M. Manno, D. W. Rench, N. Samarth, C. Leighton, and P. Schiffer, Understanding magnetotransport signatures in networks of connected permalloy nanowires, Phys. Rev. B 95, 060405(R) (2017)

Ian Gilbert, Yuyang Lao, Isaac Carrasquillo, Liam O’Brien, Justin D. Watts, Michael Manno, Chris Leighton, Andreas Scholl, Cristiano Nisoli and Peter Schiffer, Emergent reduced dimensionality by vertex frustration in artificial spin ice, Nat. Phys. 12, 162 (2015)

Hong Lu, Daniel G. Ouellette, Sascha Preu, Justin D. Watts, Benjamin Zaks, Peter G. Burke, Mark S. Sherwin,and Arthur C. Gossard, Self-assembled ErSb nanostructures with optical applications in Infrared and Terahertz, Nano Lett. 14, 1107 (2014)

Education

B.S. with honors in Physics: University of California, Santa Barbara - 2013