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

News and information

Built to last: New copolymer binder to extend the life of lithium ion batteries: Scientists develop a novel binder material that protects the graphite anode of Li-ion batteries from degradation even after 1700 cycles March 5th, 2021

A COSMIC approach to nanoscale science: Instrument at Berkeley Lab's Advanced Light Source achieves world-leading resolution of nanomaterials March 5th, 2021

Light in concert with force reveals how materials become harder when illuminated: When indented by a probe in darkness, wafers of some semiconductors are putty-like. When illuminated by light whose wavelength matches the band gap, they become hard, as electrons and holes freed by March 5th, 2021

Taking 2D materials for a spin: Scientists at the University of Tsukuba and the Institute of High Pressure Physics fabricate a novel molybdenum disulfide transistor and create an image of the spins of the electrons passing through which may open the way for new spintronic compute March 5th, 2021

Graphene/ Graphite

Expanding the freedom of design: powder coating on FRP thanks to conductive gelcoats with graphene nanotubes March 3rd, 2021

Engineering the boundary between 2D and 3D materials: Cutting-edge microscope helps reveal ways to control the electronic properties of atomically thin materials February 26th, 2021

Grapheal raises EUR1.9 million to advance development of embedded biosensing technology and application in digital COVID testing and wound monitoring: Includes seed financing from Novalis Biotech and private investors, support from Bpifrance as well as non-dilutive grants February 10th, 2021

A little soap simplifies making 2D nanoflakes: Rice labís experiments refine processing of hexagonal boron nitride January 27th, 2021

Researchers develop new graphene nanochannel water filters January 22nd, 2021

Physics

Atomic nuclei in the quantum swing: The extremely precise control of nuclear excitations opens up possibilities of ultra-precise atomic clocks and powerful nuclear batteries February 19th, 2021

D-Wave demonstrates performance advantage in quantum simulation of exotic magnetism: Fully-programmable annealing quantum computer demonstrates 3 million times speed-up over classical CPU in a practical application February 19th, 2021

Superconductivity

Nanowire could provide a stable, easy-to-make superconducting transistor: Inspired by decades-old MIT research, the new technology could boost quantum computers and other superconducting electronics February 12th, 2021

Govt.-Legislation/Regulation/Funding/Policy

A COSMIC approach to nanoscale science: Instrument at Berkeley Lab's Advanced Light Source achieves world-leading resolution of nanomaterials March 5th, 2021

Arrowhead Pharmaceuticals Files IND to Begin Phase 2b Study of ARO-APOC3 in Patients with Severe Hypertriglyceridemia March 2nd, 2021

Quantum quirk yields giant magnetic effect, where none should exist: Study opens window into the landscape of extreme topological matter March 1st, 2021

Bioinformatics tool accurately tracks synthetic: DNA Computer scientists show benefits of bioinformatics with PlasmidHawk February 26th, 2021

Possible Futures

Built to last: New copolymer binder to extend the life of lithium ion batteries: Scientists develop a novel binder material that protects the graphite anode of Li-ion batteries from degradation even after 1700 cycles March 5th, 2021

A COSMIC approach to nanoscale science: Instrument at Berkeley Lab's Advanced Light Source achieves world-leading resolution of nanomaterials March 5th, 2021

Light in concert with force reveals how materials become harder when illuminated: When indented by a probe in darkness, wafers of some semiconductors are putty-like. When illuminated by light whose wavelength matches the band gap, they become hard, as electrons and holes freed by March 5th, 2021

Taking 2D materials for a spin: Scientists at the University of Tsukuba and the Institute of High Pressure Physics fabricate a novel molybdenum disulfide transistor and create an image of the spins of the electrons passing through which may open the way for new spintronic compute March 5th, 2021

Discoveries

Built to last: New copolymer binder to extend the life of lithium ion batteries: Scientists develop a novel binder material that protects the graphite anode of Li-ion batteries from degradation even after 1700 cycles March 5th, 2021

A COSMIC approach to nanoscale science: Instrument at Berkeley Lab's Advanced Light Source achieves world-leading resolution of nanomaterials March 5th, 2021

Light in concert with force reveals how materials become harder when illuminated: When indented by a probe in darkness, wafers of some semiconductors are putty-like. When illuminated by light whose wavelength matches the band gap, they become hard, as electrons and holes freed by March 5th, 2021

Taking 2D materials for a spin: Scientists at the University of Tsukuba and the Institute of High Pressure Physics fabricate a novel molybdenum disulfide transistor and create an image of the spins of the electrons passing through which may open the way for new spintronic compute March 5th, 2021

Materials/Metamaterials

Light in concert with force reveals how materials become harder when illuminated: When indented by a probe in darkness, wafers of some semiconductors are putty-like. When illuminated by light whose wavelength matches the band gap, they become hard, as electrons and holes freed by March 5th, 2021

Expanding the freedom of design: powder coating on FRP thanks to conductive gelcoats with graphene nanotubes March 3rd, 2021

Quantum quirk yields giant magnetic effect, where none should exist: Study opens window into the landscape of extreme topological matter March 1st, 2021

Changing the silkworm's diet to spin stronger silk February 26th, 2021

Announcements

Built to last: New copolymer binder to extend the life of lithium ion batteries: Scientists develop a novel binder material that protects the graphite anode of Li-ion batteries from degradation even after 1700 cycles March 5th, 2021

A COSMIC approach to nanoscale science: Instrument at Berkeley Lab's Advanced Light Source achieves world-leading resolution of nanomaterials March 5th, 2021

Light in concert with force reveals how materials become harder when illuminated: When indented by a probe in darkness, wafers of some semiconductors are putty-like. When illuminated by light whose wavelength matches the band gap, they become hard, as electrons and holes freed by March 5th, 2021

Taking 2D materials for a spin: Scientists at the University of Tsukuba and the Institute of High Pressure Physics fabricate a novel molybdenum disulfide transistor and create an image of the spins of the electrons passing through which may open the way for new spintronic compute March 5th, 2021

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

Built to last: New copolymer binder to extend the life of lithium ion batteries: Scientists develop a novel binder material that protects the graphite anode of Li-ion batteries from degradation even after 1700 cycles March 5th, 2021

A COSMIC approach to nanoscale science: Instrument at Berkeley Lab's Advanced Light Source achieves world-leading resolution of nanomaterials March 5th, 2021

Light in concert with force reveals how materials become harder when illuminated: When indented by a probe in darkness, wafers of some semiconductors are putty-like. When illuminated by light whose wavelength matches the band gap, they become hard, as electrons and holes freed by March 5th, 2021

Taking 2D materials for a spin: Scientists at the University of Tsukuba and the Institute of High Pressure Physics fabricate a novel molybdenum disulfide transistor and create an image of the spins of the electrons passing through which may open the way for new spintronic compute March 5th, 2021

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

Quantum quirk yields giant magnetic effect, where none should exist: Study opens window into the landscape of extreme topological matter March 1st, 2021

Bioinformatics tool accurately tracks synthetic: DNA Computer scientists show benefits of bioinformatics with PlasmidHawk February 26th, 2021

Researchers improve efficiency of next-generation solar cell material: Reducing internal losses could pave the way to low-cost perovskite-based photovoltaics that match silicon cellsí output February 26th, 2021

Pore-like proteins designed from scratch: By creating barrel-shaped proteins that embed into lipid membranes, biochemist have expanded the bioengineering toolkit February 19th, 2021

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