A team of
researchers from Argonne’s Materials Science Division and Northern Illinois
University,
working with
researchers at Argonne’s Center for Nanoscale Materials, report two new
findings
on tungsten
ditelluride: (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 materials and assumed to be a metal-insulator
transition.
(October 20, 2015) Scientists recently discovered that
tungsten ditelluride (WTe2) is electronically three-dimensional with a low
anisotropy. Anisotropy reflects the change in properties of a material when the
direction of the current or the applied magnetic field is varied.
Similar to graphite consisting of weakly bound graphene
layers, WTe2 is a layered material that could be reduced to few layers in
thickness or a monolayer and be used in making nanoscale transistors in other
electronics. The material was originally thought to be two-dimensional in
nature because of the ease with which its layers could be separated.
WTe2 has been the subject of increased scientific interest
since a 2014 research study outlined its unusual magnetoresistance, which is
the ability of a material to change the value of its electrical resistance when
subjected to an external magnetic field.
This particular finding "is interesting in its own
right because it shows that the mechanical and electrical properties of a
material are not always as closely linked as we may assume," wrote Kamran
Behnia, director of quantum matter research at Le Centre National de la
Recherche Scientifique in Paris, in an opinion piece on the latest research
discovery about WTe2 published in journal Physics, which provides news and
commentary on select papers from American Physical Society journals.
Researchers also discovered that the anisotropy of WTe2
varies and displays the magnetoresistance behavior of the Fermi liquid state,
which is a theoretical model that describes the normal state of most metals at
sufficiently low temperatures.