Nanotechnology Now

Our NanoNews Digest Sponsors
Heifer International



Home > Press > Exploring quantum electron highways with laser light: Spiraling laser light reveals how topological insulators lose their ability to conduct electric current on their surfaces.

Diagram of an experimental setup at SLAC’s high-power laser lab where scientists used circularly polarized laser light to probe a topological insulator – a type of quantum material that conducts electric current on its surfaces but not through its interior. A process called high harmonic generation shifts the laser light to higher energies and frequencies, or harmonics, as it passes through a TI. The harmonics allow scientists to clearly distinguish what electrons are doing in the material’s conductive surface and its insulating interior.
CREDIT
Shambhu Ghimire/Stanford PULSE Institute
Diagram of an experimental setup at SLAC’s high-power laser lab where scientists used circularly polarized laser light to probe a topological insulator – a type of quantum material that conducts electric current on its surfaces but not through its interior. A process called high harmonic generation shifts the laser light to higher energies and frequencies, or harmonics, as it passes through a TI. The harmonics allow scientists to clearly distinguish what electrons are doing in the material’s conductive surface and its insulating interior. CREDIT Shambhu Ghimire/Stanford PULSE Institute

Abstract:
Topological insulators, or TIs, have two faces: Electrons flow freely along their surface edges, like cars on a superhighway, but can’t flow through the interior of the material at all. It takes a special set of conditions to create this unique quantum state – part electrical conductor, part insulator – which researchers hope to someday exploit for things like spintronics, quantum computing and quantum sensing. For now, they’re just trying to understand what makes TIs tick.

Exploring quantum electron highways with laser light: Spiraling laser light reveals how topological insulators lose their ability to conduct electric current on their surfaces.

Menlo Park, CA | Posted on August 19th, 2022

In the latest advance along those lines, researchers at the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University systematically probed the “phase transition” in which a TI loses its quantum properties and becomes just another ordinary insulator.

They did this by using spiraling beams of laser light to generate harmonics – much like the vibrations of a plucked guitar string – from the material they were examining. Those harmonics make it easy to distinguish what’s happening in the superhighway layer from what’s happening in the interior and see how one state gives way to the other, they reported in Nature Photonics today.

“The harmonics generated by the material amplify the effects we want to measure, making this a very sensitive way to see what’s going on in a TI,” said Christian Heide, a postdoctoral researcher with the Stanford PULSE Institute at SLAC, who led the experiments.

“And since this light-based approach can be done in a lab with tabletop equipment, it makes exploring these materials easier and more accessible than some previous methods.”

These results are exciting, added PULSE principal investigator Shambhu Ghimire, because they show the new method has potential for watching TIs flip back and forth between superhighway and insulating states as it happens and in fine detail – much like a using camera with a very fast shutter speed.

A long harmonics journey

This was the latest in a series of studies led by Ghimire and PULSE Director David Reis on high harmonic generation, or HHG, a phenomenon that shifts laser light to higher energies and frequencies by shining it through a material. The frequencies are shifted in distinct steps, like notes made by pressing on a guitar string.

Over the past dozen years, their research team has managed to do this in a number of materials that were thought to be unlikely or even impossible candidates for HHG, including a crystal, frozen argon gas and an atomically thin semiconductor material. They were even able to produce attosecond laser pulses – which are just a billionth of a billionth of a second long and can be used to observe and control the movements of electrons – by shining a laser through ordinary glass.

Four years ago, postdoctoral researcher Denitsa Baykusheva joined the PULSE group with the aim of seeing if it was possible to generate HHG in topological insulators – a feat that had never been achieved in any quantum material. Over several years of work the team discovered that yes, it could be done, but only if the laser light was circularly polarized.

And this spiraling laser light had a bonus: By varying its polarization, they were able to get strong, separate signals from the TI’s superhighway surface and its roadblocked interior. This allowed them to easily distinguish what was going on in those two contrasting parts of the material.

In the current study, they set out to demonstrate what the new method could do by varying the composition of their TI material, bismuth selenide, and the properties of the ultrashort pulses of laser light they hit it with to see how each combination affected the harmonics the material generated.

Spirals meet impurities

First they took their samples to SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) for examination with an X-ray technique called angle-resolved photoemission spectroscopy, or ARPES. This allowed them to narrow down the general neighborhood where the transition takes place.

Then, back in the lab, they zoomed in to see more detail.

They prepared a series of bismuth selenide samples – some pure and others containing varying levels of a chemical impurity that’s known to affect electron behavior. Some of the samples were topological insulators and others were plain insulators.

Then they hit the samples with laser pulses of different energies and degrees and directions of polarization.

They discovered that circularly polarized pulses, especially the ones that spiraled clockwise, were much more efficient at producing high harmonics from superhighway surfaces than from insulating parts of the material. “The difference between the two was huge,” Heide said, so the team could easily tell the two states apart.

While pure samples were classic TIs, the material began to lose its topological abilities at an impurity level of about 4% and lost them altogether by 20%. At that point the material was an ordinary insulator.

The ultrashort laser pulses used in this study – about 100 femtoseconds, or millionths of a billionth of a second, long – pass right through the sample without damaging it, and can be tuned to probe any spot inside it, Heide said: “That’s a very big benefit.”

And like a camera with a super-fast shutter speed, this relatively small and affordable laser setup should be able to observe the characteristics of the topological transition, as well as other electronic properties and processes, in much finer detail and as they change in real time, Ghimire said.

“That’s one possibility that makes this all-optical method interesting and gives it a wide range of potential applications,” he said, “and it’s something we plan to explore in future experiments.”

Researchers from SSRL, the Stanford Institute for Materials and Energy Sciences (SIMES) and Harvard University also contributed to this work, and a team at Rutgers University prepared the samples used in the experiments. The study was funded primarily by the DOE Office of Science. SSRL is a DOE Office of Science user facility.

####

About DOE/SLAC National Accelerator Laboratory
SLAC is a vibrant multiprogram laboratory that explores how the universe works at the biggest, smallest and fastest scales and invents powerful tools used by scientists around the globe. With research spanning particle physics, astrophysics and cosmology, materials, chemistry, bio- and energy sciences and scientific computing, we help solve real-world problems and advance the interests of the nation.

SLAC is operated by Stanford University for the U.S. Department of Energy’s Office of Science. The 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 click here

Contacts:
Glennda Chui
DOE/SLAC National Accelerator Laboratory

Office: 510-507-2766

Copyright © DOE/SLAC National Accelerator 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 Links

Citation: Christian Heide et al., Nature Photonics, 18 August 2022 (10.1038/s41566-022-01050-7):

Related News Press

News and information

Drawing data in nanometer scale September 30th, 2022

Researchers unveil mystery inside Li- o2 batteries September 30th, 2022

Synthesis of air-stable room-temperature van der Waals magnetic thin flakes September 30th, 2022

ACM Research Launches New Furnace Tool for Thermal Atomic Layer Deposition to Support Advanced Semiconductor Manufacturing Requirements: Ultra Fn A Furnace Tool Shipped to China-Based Foundry Customer September 30th, 2022

Laboratories

Solvent study solves solar cell durability puzzle: Rice-led project could make perovskite cells ready for prime time September 23rd, 2022

New cathode design solves major barrier to better lithium-ion batteries September 9th, 2022

Quantum Physics

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

Lattice distortion of perovskite quantum dots induces coherent quantum beating September 9th, 2022

Bound by light: Glass nanoparticles show unexpected coupling when levitated with laser light August 26th, 2022

Govt.-Legislation/Regulation/Funding/Policy

Drawing data in nanometer scale September 30th, 2022

New technique allows researchers to scrape beyond the surface of nanomaterials: Using a new secondary-ion mass spectrometry technique, research are getting a fresh look at MXenes and MAX phases September 23rd, 2022

Solvent study solves solar cell durability puzzle: Rice-led project could make perovskite cells ready for prime time September 23rd, 2022

Heat-resistant nanophotonic material could help turn heat into electricity: The key to beating the heat is degrading the materials in advance September 23rd, 2022

Possible Futures

Researchers unveil mystery inside Li- o2 batteries September 30th, 2022

Synthesis of air-stable room-temperature van der Waals magnetic thin flakes September 30th, 2022

Layer Hall effect and hidden Berry curvature in antiferromagnetic insulators September 30th, 2022

ACM Research Launches New Furnace Tool for Thermal Atomic Layer Deposition to Support Advanced Semiconductor Manufacturing Requirements: Ultra Fn A Furnace Tool Shipped to China-Based Foundry Customer September 30th, 2022

Spintronics

Synthesis of air-stable room-temperature van der Waals magnetic thin flakes September 30th, 2022

New road towards spin-polarised currents September 9th, 2022

Scientists take control of magnetism at the microscopic level: Neutrons reveal remarkable atomic behavior in thermoelectric materials for more efficient conversion of heat into electricity August 26th, 2022

Rensselaer researchers learn to control electron spin at room temperature to make devices more efficient and faster: Electron spin, rather than charge, holds the key July 15th, 2022

Quantum Computing

Synthesis of air-stable room-temperature van der Waals magnetic thin flakes September 30th, 2022

Chicago Quantum Exchange welcomes six new partners highlighting quantum technology solutions, from Chicago and beyond September 23rd, 2022

Upgrading your computer to quantum September 23rd, 2022

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

Sensors

Silicon image sensor that computes: Device speeds up, simplifies image processing for autonomous vehicles and other applications August 26th, 2022

Engineers fabricate a chip-free, wireless electronic “skin”: The device senses and wirelessly transmits signals related to pulse, sweat, and ultraviolet exposure, without bulky chips or batteries August 19th, 2022

‘Life-like’ lasers can self-organise, adapt their structure, and cooperate July 15th, 2022

CEA-Leti Barn-Owl Inspired, Object-Localization System Uses Up to ‘5 Orders of Magnitude’ Less Energy than Existing Technology: Paper in Nature Communications Describes Neuromorphic Computing Device With ‘Virtually No Power Consumption’ When Idle, Thanks to On-Chip Non-Volatile M July 8th, 2022

Discoveries

Surface microstructures of lunar soil returned by Chang’e-5 mission reveal an intermediate stage in space weathering process September 30th, 2022

Researchers unveil mystery inside Li- o2 batteries September 30th, 2022

Synthesis of air-stable room-temperature van der Waals magnetic thin flakes September 30th, 2022

Layer Hall effect and hidden Berry curvature in antiferromagnetic insulators September 30th, 2022

Announcements

Researchers unveil mystery inside Li- o2 batteries September 30th, 2022

Synthesis of air-stable room-temperature van der Waals magnetic thin flakes September 30th, 2022

Layer Hall effect and hidden Berry curvature in antiferromagnetic insulators September 30th, 2022

ACM Research Launches New Furnace Tool for Thermal Atomic Layer Deposition to Support Advanced Semiconductor Manufacturing Requirements: Ultra Fn A Furnace Tool Shipped to China-Based Foundry Customer September 30th, 2022

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

Conformal optical black hole for cavity September 30th, 2022

Cleveland researchers reveal new strategy to prevent blood clots without increasing the risk of bleeding: University Hospitals and Case Western Reserve University findings may be especially impactful for cancer patients who experience blood clot complications September 30th, 2022

Ultrasmall VN/Co heterostructure with optimized N active sites anchored in N-doped graphitic nanocarbons for boosting hydrogen evolution September 30th, 2022

Layer Hall effect and hidden Berry curvature in antiferromagnetic insulators September 30th, 2022

Photonics/Optics/Lasers

“Twisty” photons could turbocharge next-gen quantum communication: Team’s on-chip technology uses orbital angular momentum to encode more information into a single photon September 23rd, 2022

Purdue researchers suggest novel way to generate a light source made from entangled photons: This research shows promise in establishing the measurement of entangled photons down to the attosecond, and possibly even zeptosecond September 9th, 2022

Chiral quasi bound states in the continuum for high-purity circularly polarized light source: Researchers demonstrate high-purity, highly directional, and high-Q circularly polarized light source from spontaneous emission to laser September 9th, 2022

New road towards spin-polarised currents September 9th, 2022

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