Scientists Discover New Magnet with Nearly Massless Charge Carriers
07/28/2017
The magnetic and electronic states of newly discovered Sr1-yMn1-zSb2 are depicted
by spheres representing the positions of the atoms in the crystal structure of this
material with strontium (Sr) depicted by the small violet spheres; antimony (Sb) by
the large blue spheres; and manganese (Mn) by the purple spheres. The arrows attached
to the Mn atoms represent the magnetic moments of these atoms which align in the orientation
shown to give the magnetic properties of Sr1-yMn1-zSb2. Also depicted are the energy
and momentum states of the conducting electrons, or charge carriers, which have a
Dirac-like dispersion relation shown in gold.Photo Credit: Oak Ridge National Laboratory
BATON ROUGE – Advances in modern electronics has demanded the requisite hardware,
transistors, to be smaller in each new iteration. Recent progress in nanotechnology
has reduced the size of silicon transistors down to the order of 10 nanometers. However,
for such small transistors, other physical effects set in, which limit their functionality.
For example, the power consumption and heat production in these devices is creating
significant problems for device design. Therefore, novel quantum materials and device
concepts are required to develop a new generation of energy-saving information technology.
The recent discoveries of topological materials — a new class of relativistic quantum
materials — hold great promise for use in energy saving electronics.
Researchers in the Louisiana Consortium for Neutron Scattering, or LaCNS, led by LSU
Department of Physics & Astronomy Chair and Professor John F. DiTusa and Tulane University
Professor Zhiqiang Mao, with collaborators at Oak Ridge National Lab, the National
High Magnetic Field Laboratory, Florida State University, and the University of New
Orleans, recently reported the first observation of this topological behavior in a
magnet, Sr1-yMn1-zSb2 (y, z < 0.1). These results were published this week in Nature
Materials (doi:10.1038/nmat4953).
“This first observation is a significant milestone in the advancement of novel quantum
materials and this discovery opens the opportunity to explore its consequences. The
nearly massless behavior of the charge carriers offers possibilities for novel device
concepts taking advantage of the extremely low power dissipation,” DiTusa said.
The phrase “topological materials” refers to materials where the current carrying
electrons act as if they have no mass similar to the properties of photons, the particles
that make up light. Amazingly, these electronic states are robust and immune to defects
and disorder because they are protected from scattering by symmetry. This symmetry
protection results in exceedingly high charge carrier mobility, creating little to
no resistance to current flow. The result is expected to be a substantial reduction
in heat production and energy saving efficiencies in electronic devices.
This new magnet displays electronic charge carriers that have almost no mass. The
magnetism brings with it an important symmetry breaking property – time reversal symmetry,
or TRS, breaking where the ability to run time backward would no longer return the
system back to its starting conditions. The combination of relativistic electron behavior,
which is the cause of much reduced charge carrier mass, and TRS breaking has been
predicted to cause even more unusual behavior, the much sought after magnetic Weyl
semimetal phase. The material discovered by this collaboration is thought to be an
excellent one to investigate for evidence of the Weyl phase and to uncover its consequences.
The researchers involved include J.Y. Liu, J. Hu, Y.L. Zhu, G.F. Cheng, X. Liu, J.
Wei, and Z.Q. Mao (Tulane University, New Orleans); Q. Zhang, W. A. Phelan, and J.
F. DiTusa (Louisiana State University, Baton Rouge); D. Graf, (National High Magnetic
Field Lab, Tallahassee); Q. Zhang, H.B. Cao and D. A. Tennant (Oak Ridge National
Laboratory); S.M.A. Radmanesh, D.J. Adams, and L. Spinu (University of New Orleans);
Marcelo Jaime and Fedor Balakirev (Condensed Matter and Magnet Science, MPA-CMMS);
and I. Chiorescu (NHFML and Florida State University, Tallahassee).
Support for this research was provided by the U.S. Department of Energy Office of
Science, the National Science Foundation and the Louisiana Board of Regents.
Additional Link:
“A magnetic topological semimetal Sr1-yMn1-zSb2 (y, z < 0.1),” Nature Materials (doi:10.1038/nmat4953): http://www.nature.com/nmat/journal/vaop/ncurrent/full/nmat4953.html
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LSU Media Relations
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