Traveling electrons in loosely bound layers

September 25, 2015, Argonne National Laboratory

Extremely large magnetoresistance (XMR) was recently discovered in WTe2, triggering extensive research on this material regarding the XMR origin. Since WTe2 is a layered compound with metal layers sandwiched between adjacent insulating chalcogenide layers, this material has been considered to be electronically two-dimensional. Here a team of users from Argonne's Materials Science Division and Northern Illinois University, working collaboratively with researchers at Argonne's Center for Nanoscale Materials, report two new findings on WTe2: (1) WTe2 is electronically three-dimensional with a mass anisotropy as low as 2, and (2) the mass anisotropy varies with temperature and follows the magnetoresistance behavior of the Fermi liquid state.

The results not only provide a general scaling approach for the anisotropic magnetoresistance but also are crucial for correctly understanding the electronic properties of WTe2, including the origin of the remarkable "turn-on" behavior in the resistance versus temperature curve, which has been widely observed in many and assumed to be a metal-insulator transition.

It remains to be seen whether this unique electronic behavior is the origin of WTe2's magnetoresistance—a property of interest for designing magnetic hard drives and sensors – but the result shows that the mechanical and electrical properties of a material are not always as closely linked as commonly assumed.

CNM facilities provided photolithographic patterning and deposition and morphological analysis via SEM. 4-probe resistivity measurements via PPMS and quantum oscillations of resistivity were performed in MSD.

Explore further: Unstoppable magnetoresistance

More information: "Temperature-Dependent Three-Dimensional Anisotropy of the Magnetoresistance in WTe2" arxiv.org/pdf/1506.02214.pdf

"Electrons Travel Between Loosely Bound Layers," Viewpoint in Physics 8, 71 (2015)

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