17 September 2018

Destruction of Weyl nodes and a new state in tantalum arsenide above 80 teslas

Electrical resistivity of TaAs for temperatures from 20K to 0.7K. Electrical resistivity of TaAs for temperatures from 20K to 0.7K.

Weyl metals such as tantalum arsenide (TaAs) are predicted to have novel properties arising from a chirality of their electron spins. Scientists induced an imbalance between the left- and right-handed spin states, resulting in a topologically protected current. This was the first time this phenomenon, known as the chiral anomaly, has been observed.

What did scientists discover?

From 20 to 50 teslas, scientists found the electrical resistivity (for parallel electric and magnetic fields) to be nearly independent of magnetic field. This is highly unusual for a conventional metal, but consistent with the strange behavior of Weyl fermions. Above 50 teslas, scientists observed a two-order-of-magnitude increase in resistivity, indicating the destruction of the Weyl nodes by the opening of an energy gap. Above 80 teslas, they observed strong ultrasonic attenuation at temperatures below 2 Kelvin, suggesting a new, mesoscopically-textured state of matter.

Why is this important?

THE TOOLS THEY USED

This research was conducted in the 65-Tesla Multi-Shot Magnet and the 100 Tesla Multi-Shot Magnet at the Pulsed Field Facility.

Fundamentally, strong spin-orbit coupled metals provide a wealth of new phenomena that are not known to exist outside of materials physics. The topological nature of the resulting states not only makes them robust against perturbation, but provides a possible bridge of the quantum-material to quantum-information chasm.

Who did the research?

B.J. Ramshaw,1, 2 K.A. Modic,3 Arkady Shekhter,4 Yi Zhang,2 Eun-Ah Kim,2 Philip J.W. Moll,3 Maja Bachmann,3 M.K. Chan,1 J.B. Betts,1 F. Balakirev,1 A. Migliori,1 N.J. Ghimire,5, 1 E.D. Bauer,1 F. Ronning,1 and Ross D. McDonald1

1Los Alamos National Laboratory, 2Laboratory of Atomic and Solid State Physics, Cornell University, 3Max-Planck-Institute for Chemical Physics of Solids, 4National MagLab, 5Argonne National Laboratory

Why did they need the MagLab?

Multiple measurements of the conductivity, sound velocity and attenuation above 90 teslas is only possible at the MagLab.

Details for scientists

Funding

This research was funded by the following grants: G.S. Boebinger (NSF DMR-1157490, NSF DMR-1644779); B.J. Ramshaw (LANL LDRD-ECR20160616 “New States of Matter in Weyl Semimetals”); M.K. Chan (DOE-BES “Science at 100 T program”); R.D. McDonald (LANL LDRD-DR20160085 “Topology and Strong Correlations” );


For more information, contact Ross McDonald.

Details

  • Research Area: Topological Matter
  • Research Initiatives: Materials
  • Facility / Program: Pulsed Field
  • Year: 2018
Last modified on 30 September 2018