Nanotechnology Now

Our NanoNews Digest Sponsors
Heifer International



Home > Press > New advance in superconductors with 'twist' in rhombohedral graphite

Electronic phase separation in multilayer rhombohedral graphite

CREDIT
The University of Manchester
Electronic phase separation in multilayer rhombohedral graphite CREDIT The University of Manchester

Abstract:
An international research team led by The University of Manchester has revealed a nanomaterial that mirrors the "magic angle" effect originally found in a complex man-made structure known as twisted bilayer graphene - a key area of study in physics in recent years.

New advance in superconductors with 'twist' in rhombohedral graphite

Manchester, UK | Posted on August 14th, 2020

The new research shows that the special topology of rhombohedral graphite effectively provides an inbuilt "twist" and therefore offers an alternative medium to study potentially game-changing effects like superconductivity. "It is an interesting alternative to highly popular studies of magic-angle graphene" said graphene pioneer Professor Sir Andre Geim, a co-author of the study.

The team, led by Artem Mishchenko, Professor of Condensed Matter Physics at The University of Manchester published its findings in the journal Nature on 12 August 2020.

"Rhombohedral graphite can help to better understand materials in which strong electronic correlations are important - such as heavy-fermion compounds and high-temperature superconductors", said Professor Mishchenko.

A previous step-forward in two-dimensional materials research was the curious behaviour that stacking one sheet of graphene atop one another and twisting it to a 'magic angle' changed the bilayer's properties, turning it into a superconductor.

Professor Mishchenko and his colleagues have now observed the emergence of strong electron-electron interactions in a weakly stable rhombohedral form of graphite - the form in which graphene layers stack slightly differently compared to stable hexagonal form.

Interactions in twisted bilayer graphene are exceptionally sensitive to the twist angle. Tiny deviations of about 0.1 degree from the exact magic angle strongly supress interactions. It is extremely difficult to make devices with the required accuracy and, especially, find sufficiently uniform ones to study the exciting physics involved. The newly published findings on rhombohedral graphite has now opened an alternative route to accurately making superconductor devices.

Graphite, a carbon material made up of stacked graphene layers, has two stable forms: hexagonal and rhombohedral. The former is more stable, and has thus been extensively studied, while the latter is less so.

To better understand the new result, it is important to remember that the graphene layers are stacked in different ways in these two forms of graphite. Hexagonal graphite (the form of carbon found in pencil lead) is composed of graphene layers orderly stacked on top of each other. The metastable rhombohedral form has a slightly different stacking order, and this slight difference leads to a drastic change in its electronic spectrum.

Previous theoretical studies have pointed to the existence of all kinds of many-body physics in the surface states of rhombohedral graphite - including high-temperature magnetic ordering and superconductivity. These predictions could not be verified, however, since electron transport measurements on the material were completely lacking until now.

The Manchester team has been studying hexagonal graphite films for several years and have developed advanced technologies to produce high-quality samples. One of their techniques involves encapsulating the films with an atomically-flat insulator, hexagonal boron nitride (hBN), which serves to preserve the high electronic quality in the resulting hBN/hexagonal graphite/hBN heterostructures. In their new experiments on rhombohedral graphite, the researchers modified their technology to preserve the fragile stacking order of this less stable form of graphite.

The researchers imaged their samples, which contained up to 50 layers of graphene, using Raman spectroscopy to confirm that the stacking order in the material remained intact and that it was of high quality. They then measured electronic transport properties of their samples in the traditional way - by recording the resistance of the material as they changed the temperature and the strength of a magnetic field applied to it.

The energy gap can also be opened in the surface states of rhombohedral graphite by applying an electric field explains Professor Mishchenko: "The surface-state gap opening, which was predicted theoretically, is also an independent confirmation of the rhombohedral nature of the samples, since such a phenomenon is forbidden in hexagonal graphite."

In rhombohedral graphite thinner than 4nm, a band gap is present even without applying an external electric field. The researchers say they are as yet unsure of the exact nature of this spontaneous gap opening (which occurs at the "charge neutrality"- the point at which densities of electrons and holes are balanced), but they are busy working on answering this question.

"From our experiments in the quantum Hall regime, we see that the gap is of a quantum spin Hall nature, but we do not know whether the spontaneous gap opening at the charge neutrality is of the same origin," adds Professor Mishchenko. "In our case, this gap opening was accompanied by hysteretic behaviour of the material's resistance as a function of applied electric or magnetic fields. This hysteresis (in which the resistance change lags behind the applied fields) implies that there are different electronic gapped phases separated into domains - and these are typical of strongly correlated materials."

Further investigation of rhombohedral graphite could shed more light on the origin of many-body phenomena in strongly correlated materials such as heavy-fermion compounds and high-temperature superconductors, to name but two examples.

####

For more information, please click here

Contacts:
Ben Robinson


@UoMNews

Copyright © University of Manchester

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

RELATED JOURNAL ARTICLE:

Related News Press

Physics

Unlocking quantum potential: Harnessing high-dimensional quantum states with QDs and OAM: Generation of nearly deterministic OAM-based entangled states offers a bridge between photonic technologies for quantum advancements September 8th, 2023

Researchers discover a potential application of unwanted electronic noise in semiconductors: Random telegraph noises in vanadium-doped tungsten diselenide can be tuned with voltage polarity August 11th, 2023

Unveiling the quantum dance: Experiments reveal nexus of vibrational and electronic dynamics: Coupling of electronic and nuclear dynamics revealed in molecules with ultrafast lasers and X-rays July 21st, 2023

News and information

Chung-Ang University researchers develop novel DNA biosensor for early diagnosis of cervical cancer: The electrochemical sensor, made of a graphitic nano-onion/molybdenum disulfide nanosheet composite, detects human papillomavirus (HPV)-16 and HPV-18, with high specificity September 8th, 2023

New compound unleashes the immune system on metastases September 8th, 2023

Machine learning contributes to better quantum error correction September 8th, 2023

Tests find no free-standing nanotubes released from tire tread wear September 8th, 2023

Graphene/ Graphite

Ribbons of graphene push the material’s potential: A new technique developed at Columbia offers a systematic evaluation of twist angle and strain in layered 2D materials August 11th, 2023

Two types of ultrafast mode-locking operations generation from an Er-doped fiber laser based on germanene nanosheets July 21st, 2023

Graphene-based Carbocatalysts: Synthesis, Properties, and Applications—Beyond Boundaries June 9th, 2023

With new experimental method, researchers probe spin structure in 2D materials for first time: By observing spin structure in “magic-angle” graphene, a team of scientists led by Brown University researchers have found a workaround for a long-standing roadblock in the field of two May 12th, 2023

Superconductivity

Research breakthrough could be significant for quantum computing future: Irish-based scientists confirm crucial characteristic of new superconductor material June 30th, 2023

Researchers at Purdue discover superconductive images are actually 3D and disorder-driven fractals May 12th, 2023

Govt.-Legislation/Regulation/Funding/Policy

Previously unknown pathway to batteries with high energy, low cost and long life: Newly discovered reaction mechanism overcomes rapid performance decline in lithium-sulfur batteries September 8th, 2023

Quantum powers researchers to see the unseen September 8th, 2023

Chloride ions from seawater eyed as possible lithium replacement in batteries of the future August 11th, 2023

Tattoo technique transfers gold nanopatterns onto live cells August 11th, 2023

Possible Futures

Chung-Ang University researchers develop novel DNA biosensor for early diagnosis of cervical cancer: The electrochemical sensor, made of a graphitic nano-onion/molybdenum disulfide nanosheet composite, detects human papillomavirus (HPV)-16 and HPV-18, with high specificity September 8th, 2023

New compound unleashes the immune system on metastases September 8th, 2023

Machine learning contributes to better quantum error correction September 8th, 2023

Tests find no free-standing nanotubes released from tire tread wear September 8th, 2023

Discoveries

Electronic detection of DNA nanoballs enables simple pathogen detection Peer-Reviewed Publication September 8th, 2023

Training quantum computers: physicists win prestigious IBM Award September 8th, 2023

Unlocking quantum potential: Harnessing high-dimensional quantum states with QDs and OAM: Generation of nearly deterministic OAM-based entangled states offers a bridge between photonic technologies for quantum advancements September 8th, 2023

Tests find no free-standing nanotubes released from tire tread wear September 8th, 2023

Materials/Metamaterials/Magnetoresistance

Ultrafast lasers for materials processing August 11th, 2023

Ribbons of graphene push the material’s potential: A new technique developed at Columbia offers a systematic evaluation of twist angle and strain in layered 2D materials August 11th, 2023

Understanding the diverse industrial applications of materials science: Materials Science A Field of Diverse Industrial Applications July 21st, 2023

A non-covalent bonding experience: Scientists discover new structures for unique hybrid materials by altering their chemical bonds July 21st, 2023

Announcements

Electronic detection of DNA nanoballs enables simple pathogen detection Peer-Reviewed Publication September 8th, 2023

Training quantum computers: physicists win prestigious IBM Award September 8th, 2023

Machine learning contributes to better quantum error correction September 8th, 2023

Tests find no free-standing nanotubes released from tire tread wear September 8th, 2023

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

Electronic detection of DNA nanoballs enables simple pathogen detection Peer-Reviewed Publication September 8th, 2023

Unlocking quantum potential: Harnessing high-dimensional quantum states with QDs and OAM: Generation of nearly deterministic OAM-based entangled states offers a bridge between photonic technologies for quantum advancements September 8th, 2023

Chung-Ang University researchers develop novel DNA biosensor for early diagnosis of cervical cancer: The electrochemical sensor, made of a graphitic nano-onion/molybdenum disulfide nanosheet composite, detects human papillomavirus (HPV)-16 and HPV-18, with high specificity September 8th, 2023

New compound unleashes the immune system on metastases September 8th, 2023

Grants/Sponsored Research/Awards/Scholarships/Gifts/Contests/Honors/Records

Training quantum computers: physicists win prestigious IBM Award September 8th, 2023

The present and future of computing get a boost from new research July 21st, 2023

Manchester graphene spin-out signs $1billion game-changing deal to help tackle global sustainability challenges: Landmark deal for the commercialisation of graphene April 14th, 2023

Optical switching at record speeds opens door for ultrafast, light-based electronics and computers: March 24th, 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