Nanotechnology Now

Our NanoNews Digest Sponsors
Heifer International



Home > Press > Channeling valleytronics in graphene: Berkeley Lab researchers discover 1-D conducting channels in bilayer graphene

In this near-field infrared nanoscopy image of bilayer graphene, domain walls are revealed by bright lines that arise because of the walls' local electronic structures and IR responses.
CREDIT: Image courtesy of Feng Wang, Berkeley Lab
In this near-field infrared nanoscopy image of bilayer graphene, domain walls are revealed by bright lines that arise because of the walls' local electronic structures and IR responses.

CREDIT: Image courtesy of Feng Wang, Berkeley Lab

Abstract:
To the list of potential applications of graphene - a two-dimensional semiconductor of pure carbon that is stronger and much faster than silicon - we can now add valleytronics, the coding of data in the wavelike motion of electrons as they speed through a conductor. Berkeley Lab researchers have discovered topologically protected one-dimensional electron conducting channels at the domain walls of bilayer graphene. These conducting channels are "valley polarized," which means they can serve as filters for electron valley polarization in future devices such as quantum computers.

Channeling valleytronics in graphene: Berkeley Lab researchers discover 1-D conducting channels in bilayer graphene

Berkeley, CA | Posted on May 6th, 2015

"Combining near-field infrared nanometer-scale microscopy and low-temperature electrical transport measurements, we have recorded the first experimental observations of 1D ballistic electron conducting channels at bilayer graphene domain walls," says Feng Wang, a condensed matter physicist with Berkeley Lab's Materials Sciences Division, who led this work. "These 1D valley-polarized conducting channels featured a ballistic length of about 400 nanometers at 4 kelvin. Their existence opens up opportunities for exploring unique topological phases and valley physics in graphene."

Wang, who also holds an appointment with the University of California (UC) Berkeley Physics Department and is a member of the Kavli Energy NanoScience Institute (Kavli-ENSI), is the corresponding author of a paper describing this research in the journal Nature. The lead authors of the paper are Long Ju and Zhiwen Shi, members of Wang's research group. (See here for full list of authors.)

Valleytronics is generating a lot of excitement in the high-tech industry as a potential avenue to quantum computing. Like spintronics, valleytronics offers a tremendous advantage in data processing speeds over the electrical charge used in classical electronics.

"In valleytronics, electrons move through the lattice of a 2D semiconductor as a wave with two energy valleys, each valley being characterized by a distinct momentum and quantum valley number," Wang says. "This quantum valley number can be used to encode information when the electrons are in a minimum energy valley."

Recent theoretical work suggested that domain walls between AB- and BA-stacked bilayer graphene could provide an attractive place to realize one-dimensional electron conducting channels for valleytronics because the smoothness of the domain walls preserves electron valleys, unlike the atomic defects at graphene edges that result in valley-mixing. Until now, however, there has been no experimental evidence of these channels.

Working at Berkeley Lab's Advanced Light Source (ALS), a DOE Office of Science User Facility, Wang, Ju, Shi and their colleagues used tightly focused beams of infrared light to image in situ bilayer graphene layer-stacking domain walls on device substrates. Field effect devices fabricated over these domain walls revealed the 1D conducting channels.

In the bilayer graphene imaging work by Feng Wang and his group, IR light (yellow) is focused onto the apex of a metal-coated AFM tip and the backscattered infrared radiation is collected and measured.

"The infrared measurements were carried out at ALS beamline 5.4," says Shi. "The near-field infrared capabilities of this beamline enable optical spectroscopy with spatial resolutions that are way beyond the diffraction limit, allowing us to image the nanometer-wide domain walls in bilayer graphene."

Adds Ju, "That we were able to image the domain walls with a technique that is compatible with device fabrication was key to our work. With near-field IR spectroscopy, we could directly fabricate field effect devices over the domain walls and detect the 1D conducting channels."

To date, most valleytronics research has focused on the 2D semiconductors known as MX2 materials, which consist of a single layer of transition metal atoms, such as molybdenum or tungsten, sandwiched between two layers of chalcogen atoms, such as sulfur. The results of this study demonstrate that protected topological phases can also be realized in bilayer graphene, which is a tunable semiconductor, making the 2D carbon sheets useful for valleytronic applications.

"Our next step is to increase the ballistic length of these 1D channels so we can utilize them as electron valley filters, as well as for other manipulations of electron valleys in graphene," Wang says.

###

This research was primarily funded by the DOE Office of Science.

####

About DOE/Lawrence Berkeley National Laboratory
Lawrence Berkeley National Laboratory addresses the world's most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab's scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy's Office of Science.

For more information, please click here

Contacts:
Lynn Yarris

510-486-5375

Copyright © DOE/Lawrence Berkeley National Laboratory

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Researchers develop artificial building blocks of life March 8th, 2024

How surface roughness influences the adhesion of soft materials: Research team discovers universal mechanism that leads to adhesion hysteresis in soft materials March 8th, 2024

Two-dimensional bimetallic selenium-containing metal-organic frameworks and their calcinated derivatives as electrocatalysts for overall water splitting March 8th, 2024

Curcumin nanoemulsion is tested for treatment of intestinal inflammation: A formulation developed by Brazilian researchers proved effective in tests involving mice March 8th, 2024

Imaging

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

Physics

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

Optically trapped quantum droplets of light can bind together to form macroscopic complexes March 8th, 2024

Graphene/ Graphite

First human trial shows ‘wonder’ material can be developed safely: A revolutionary nanomaterial with huge potential to tackle multiple global challenges could be developed further without acute risk to human health, research suggests February 16th, 2024

NRL discovers two-dimensional waveguides February 16th, 2024

$900,000 awarded to optimize graphene energy harvesting devices: The WoodNext Foundation's commitment to U of A physicist Paul Thibado will be used to develop sensor systems compatible with six different power sources January 12th, 2024

Laboratories

A battery’s hopping ions remember where they’ve been: Seen in atomic detail, the seemingly smooth flow of ions through a battery’s electrolyte is surprisingly complicated February 16th, 2024

NRL discovers two-dimensional waveguides February 16th, 2024

Govt.-Legislation/Regulation/Funding/Policy

What heat can tell us about battery chemistry: using the Peltier effect to study lithium-ion cells March 8th, 2024

Researchers’ approach may protect quantum computers from attacks March 8th, 2024

The Access to Advanced Health Institute receives up to $12.7 million to develop novel nanoalum adjuvant formulation for better protection against tuberculosis and pandemic influenza March 8th, 2024

Optically trapped quantum droplets of light can bind together to form macroscopic complexes March 8th, 2024

Chip Technology

New chip opens door to AI computing at light speed February 16th, 2024

HKUST researchers develop new integration technique for efficient coupling of III-V and silicon February 16th, 2024

Electrons screen against conductivity-killer in organic semiconductors: The discovery is the first step towards creating effective organic semiconductors, which use significantly less water and energy, and produce far less waste than their inorganic counterparts February 16th, 2024

NRL discovers two-dimensional waveguides February 16th, 2024

Quantum Computing

Researchers’ approach may protect quantum computers from attacks March 8th, 2024

Physicists ‘entangle’ individual molecules for the first time, hastening possibilities for quantum information processing: In work that could lead to more robust quantum computing, Princeton researchers have succeeded in forcing molecules into quantum entanglement December 8th, 2023

World’s first logical quantum processor: Key step toward reliable quantum computing December 8th, 2023

Optical-fiber based single-photon light source at room temperature for next-generation quantum processing: Ytterbium-doped optical fibers are expected to pave the way for cost-effective quantum technologies November 3rd, 2023

Nanoelectronics

Interdisciplinary: Rice team tackles the future of semiconductors Multiferroics could be the key to ultralow-energy computing October 6th, 2023

Key element for a scalable quantum computer: Physicists from Forschungszentrum Jülich and RWTH Aachen University demonstrate electron transport on a quantum chip September 23rd, 2022

Reduced power consumption in semiconductor devices September 23rd, 2022

Atomic level deposition to extend Moore’s law and beyond July 15th, 2022

Discoveries

What heat can tell us about battery chemistry: using the Peltier effect to study lithium-ion cells March 8th, 2024

Researchers’ approach may protect quantum computers from attacks March 8th, 2024

High-tech 'paint' could spare patients repeated surgeries March 8th, 2024

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

Announcements

What heat can tell us about battery chemistry: using the Peltier effect to study lithium-ion cells March 8th, 2024

Curcumin nanoemulsion is tested for treatment of intestinal inflammation: A formulation developed by Brazilian researchers proved effective in tests involving mice March 8th, 2024

The Access to Advanced Health Institute receives up to $12.7 million to develop novel nanoalum adjuvant formulation for better protection against tuberculosis and pandemic influenza March 8th, 2024

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

Interviews/Book Reviews/Essays/Reports/Podcasts/Journals/White papers/Posters

Researchers develop artificial building blocks of life March 8th, 2024

How surface roughness influences the adhesion of soft materials: Research team discovers universal mechanism that leads to adhesion hysteresis in soft materials March 8th, 2024

Curcumin nanoemulsion is tested for treatment of intestinal inflammation: A formulation developed by Brazilian researchers proved effective in tests involving mice March 8th, 2024

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

Tools

First direct imaging of small noble gas clusters at room temperature: Novel opportunities in quantum technology and condensed matter physics opened by noble gas atoms confined between graphene layers January 12th, 2024

New laser setup probes metamaterial structures with ultrafast pulses: The technique could speed up the development of acoustic lenses, impact-resistant films, and other futuristic materials November 17th, 2023

Ferroelectrically modulate the Fermi level of graphene oxide to enhance SERS response November 3rd, 2023

The USTC realizes In situ electron paramagnetic resonance spectroscopy using single nanodiamond sensors November 3rd, 2023

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project