18 November 2020

Spontaneous "Valley Magnetization" in an Atomically-thin Semiconductor

Left: The tungsten di-selenide (WSe2) monolayer-on-fiber assembly used for optical absorption studies in 60 tesla magnetic fields., Right:  Discrete jumps in the absorption indicate emptying and spontaneous filling of specific quantum states (the “valley”states). Left: The tungsten di-selenide (WSe2) monolayer-on-fiber assembly used for optical absorption studies in 60 tesla magnetic fields., Right: Discrete jumps in the absorption indicate emptying and spontaneous filling of specific quantum states (the “valley”states). Jing Li

Interactions between electrons underpin some of the most interesting – and useful -- effects in materials science and condensed-matter physics. This work demonstrates that, in the new family of so-called "monolayer semiconductors" that are only one atomic layer thick, electron-electron interactions can lead to the sudden and spontaneous formation of a magnetized state, analogous to the appearance of magnetism in conventional materials like iron.

What did scientists discover?

In a single atomically-thin layer of the semiconductor WSe2, optical studies have shown that all of the electrons in the material can spontaneously "polarize" – or suddenly jump to the same quantum state (or "valley") in the material. This a phenomenon is directly analogous to magnetization.

THE TOOLS THEY USED

This research was conducted in the 65T pulsed magnets at the Pulsed Field Facility.

Why is this important?

Interactions between electrons are the root of some of the most interesting effects in condensed-matter physics (including magnetism). In two-dimensional ‘sheets’ of electrons in very high-quality semiconductors, interactions can result in the discovery of important new phenomena, such as the Fractional Quantum Hall Effect (for which a Nobel prize was awarded in 1998). The electron-electron interactions here could yield a new way to use valleytronic controls in magnetic information storage or other exciting applications.

Who did the research?

J. Li1, M. Goryca1, N. P. Wilson2, A. V. Stier1, X. Xu2, S. A. Crooker1

1National MagLab, Los Alamos National Laboratory; 2University of Washington

Why did they need the MagLab?

Large magnetic fields up to 60 T were essential for creating conditions wherein the 'valley magnetization' could spontaneously occur in the WSe2 monolayer semiconductor. Large fields were also needed to separate the different energy levels, so that they could be experimentally distinguished using light.

Details for scientists

Funding

This research was funded by the following grants: G.S. Boebinger (NSF DMR-1644779) S. A. Crooker (DOE BES ‘Science of 100T’, Los Alamos LDRD); X. Xu (DOE DE-SC0018171)


For more information, contact Scott A Crooker.

Details

  • Research Area: 2D,Condensed Matter Technique Development, Semiconductors
  • Research Initiatives: Materials
  • Facility / Program: Pulsed Field
  • Year: 2020
Last modified on 19 November 2020