Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

When semiconductors stick together, materials go quantum

08.03.2019

A new study led by Berkeley Lab reveals how aligned layers of atomically thin semiconductors can yield an exotic new quantum material

A team of researchers led by the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) has developed a simple method that could turn ordinary semiconducting materials into quantum machines - superthin devices marked by extraordinary electronic behavior.


The twist angle formed between atomically thin layers of tungsten disulfide and tungsten diselenide acts as a "tuning knob," turning ordinary semiconductors into an exotic quantum material.

Credit: Berkeley Lab

Such an advancement could help to revolutionize a number of industries aiming for energy-efficient electronic systems - and provide a platform for exotic new physics.

The study describing the method, which stacks together 2D layers of tungsten disulfide and tungsten diselenide to create an intricately patterned material, or superlattice, was published online recently in the journal Nature.

"This is an amazing discovery because we didn't think of these semiconducting materials as strongly interacting," said Feng Wang, a condensed matter physicist with Berkeley Lab's Materials Sciences Division and professor of physics at UC Berkeley. "Now this work has brought these seemingly ordinary semiconductors into the quantum materials space."

Two-dimensional (2D) materials, which are just one atom thick, are like nanosized building blocks that can be stacked arbitrarily to form tiny devices. When the lattices of two 2D materials are similar and well-aligned, a repeating pattern called a moiré superlattice can form.

For the past decade, researchers have been studying ways to combine different 2D materials, often starting with graphene - a material known for its ability to efficiently conduct heat and electricity. Out of this body of work, other researchers had discovered that moiré superlattices formed with graphene exhibit exotic physics such as superconductivity when the layers are aligned at just the right angle.

The new study, led by Wang, used 2D samples of semiconducting materials - tungsten disulfide and tungsten diselenide - to show that the twist angle between layers provides a "tuning knob" to turn a 2D semiconducting system into an exotic quantum material with highly interacting electrons.

Entering a new realm of physics

Co-lead authors Chenhao Jin, a postdoctoral scholar, and Emma Regan, a graduate student researcher, both of whom work under Wang in the Ultrafast Nano-Optics Group at UC Berkeley, fabricated the tungsten disulfide and tungsten diselenide samples using a polymer-based technique to pick up and transfer flakes of the materials, each measuring just tens of microns in diameter, into a stack.

They had fabricated similar samples of the materials for a previous study, but with the two layers stacked at no particular angle. When they measured the optical absorption of a new tungsten disulfide and tungsten diselenide sample for the current study, they were taken completely by surprise.

The absorption of visible light in a tungsten disulfide/tungsten diselenide device is largest when the light has the same energy as the system's exciton, a quasiparticle that consists of an electron bound to a hole that is common in 2D semiconductors. (In physics, a hole is a currently vacant state that an electron could occupy.)

For light in the energy range that the researchers were considering, they expected to see one peak in the signal that corresponded to the energy of an exciton.

Instead, they found that the original peak that they expected to see had split into three different peaks representing three distinct exciton states.

What could have increased the number of exciton states in the tungsten disulfide/tungsten device from one to three? Was it the addition of a moiré superlattice?

To find out, their collaborators Aiming Yan and Alex Zettl used a transmission electron microscope (TEM) at Berkeley Lab's Molecular Foundry, a nanoscale science research facility, to take atomic-resolution images of the tungsten disulfide/tungsten diselenide device to check how the materials' lattices were aligned.

The TEM images confirmed what they had suspected all along: the materials had indeed formed a moiré superlattice. "We saw beautiful, repeating patterns over the entire sample," said Regan. "After comparing this experimental observation with a theoretical model, we found that the moiré pattern introduces a large potential energy periodically over the device and could therefore introduce exotic quantum phenomena."

The researchers next plan to measure how this new quantum system could be applied to optoelectronics, which relates to the use of light in electronics; valleytronics, a field that could extend the limits of Moore's law by miniaturizing electronic components; and superconductivity, which would allow electrons to flow in devices with virtually no resistance.

###

Also contributing to the study were researchers from Arizona State University and the National Institute for Materials Science in Japan.

The work was supported by the DOE Office of Science. Additional funding was provided by the National Science Foundation, the Department of Defense, and the Elemental Strategy Initiative conducted by MEXT, Japan, and JSPS KAKENHI. The Molecular Foundry is a DOE Office of Science user facility.

Founded in 1931 on the belief that the biggest scientific challenges are best addressed by teams, Lawrence Berkeley National Laboratory and its scientists have been recognized with 13 Nobel Prizes. Today, Berkeley Lab researchers develop sustainable energy and environmental solutions, create useful new materials, advance the frontiers of computing, and probe the mysteries of life, matter, and the universe. Scientists from around the world rely on the Lab's facilities for their own discovery science. Berkeley Lab is a multiprogram national laboratory, managed by the University of California for the U.S. Department of Energy's Office of Science.

DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

Media Contact

Theresa Duque
tnduque@lbl.gov
510-495-2418

 @BerkeleyLab

http://www.lbl.gov 

Theresa Duque | EurekAlert!
Further information:
https://newscenter.lbl.gov/2019/03/07/semiconductors-go-quantum
http://dx.doi.org/10.1038/s41586-019-0976-y

More articles from Physics and Astronomy:

nachricht Surprising number of exoplanets could host life
31.07.2020 | University of California - Riverside

nachricht Cosmic tango between the very small and the very large
30.07.2020 | Penn State

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: TU Graz Researchers synthesize nanoparticles tailored for special applications

“Core-shell” clusters pave the way for new efficient nanomaterials that make catalysts, magnetic and laser sensors or measuring devices for detecting electromagnetic radiation more efficient.

Whether in innovative high-tech materials, more powerful computer chips, pharmaceuticals or in the field of renewable energies, nanoparticles – smallest...

Im Focus: Tailored light inspired by nature

An international research team with Prof. Cornelia Denz from the Institute of Applied Physics at the University of Münster develop for the first time light fields using caustics that do not change during propagation. With the new method, the physicists cleverly exploit light structures that can be seen in rainbows or when light is transmitted through drinking glasses.

Modern applications as high resolution microsopy or micro- or nanoscale material processing require customized laser beams that do not change during...

Im Focus: NYUAD astrophysicist investigates the possibility of life below the surface of Mars

  • A rover expected to explore below the surface of Mars in 2022 has the potential to provide more insights
  • The findings published in Scientific Reports, Springer Nature suggests the presence of traces of water on Mars, raising the question of the possibility of a life-supporting environment

Although no life has been detected on the Martian surface, a new study from astrophysicist and research scientist at the Center for Space Science at NYU Abu...

Im Focus: Manipulating non-magnetic atoms in a chromium halide enables tuning of magnetic properties

New approach creates synthetic layered magnets with unprecedented level of control over their magnetic properties

The magnetic properties of a chromium halide can be tuned by manipulating the non-magnetic atoms in the material, a team, led by Boston College researchers,...

Im Focus: A new method to significantly increase the range and stability of optical tweezers

Scientists of Tomsk Polytechnic University jointly with a team of the V.E. Zuev Institute of Atmospheric Optics of the Siberian Branch of the Russian Academy of Sciences have discovered a method to increase the operation range of optical traps also known

Optical tweezers are a device which uses a laser beam to move micron-sized objects such as living cells, proteins, and molecules. In 2018, the American...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“Conference on Laser Polishing – LaP 2020”: The final touches for surfaces

23.07.2020 | Event News

Conference radar for cybersecurity

21.07.2020 | Event News

Contact Tracing Apps against COVID-19: German National Academy Leopoldina hosts international virtual panel discussion

07.07.2020 | Event News

 
Latest News

Time To Say Goodbye: The MOSAiC floe’s days are numbered

31.07.2020 | Earth Sciences

Scientists find new way to kill tuberculosis

31.07.2020 | Life Sciences

Spin, spin, spin: researchers enhance electron spin longevity

31.07.2020 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>