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

Nanomaterials enable dual-mode heating and cooling device: Device could cut HVAC energy use by nearly 20% in the US December 2nd, 2020

Having it Both Ways: A Combined Strategy in Catalyst Design for Suzuki Cross-Couplings December 2nd, 2020

The National Space Society Remembers Ben Bova : NSS Mourns the Loss of a Visionary NSS Leader December 2nd, 2020

Arrowhead Pharmaceuticals to Participate in Upcoming Conferences December 2nd, 2020

New platform generates hybrid light-matter excitations in highly charged graphene December 2nd, 2020

Graphene/ Graphite

New platform generates hybrid light-matter excitations in highly charged graphene December 2nd, 2020

New insights into memristive devices by combining incipient ferroelectrics and graphene November 27th, 2020

Staying ahead of the curve with 3D curved graphene November 20th, 2020

Manchester group discover new family of quasiparticles in graphene-based materials: Findings to help achieve Holy Grail of 2D materials - superfast electronic devices November 13th, 2020

Flash graphene rocks strategy for plastic waste: Rice University lab detours potential environmental hazard into useful material October 30th, 2020

Physics

Pitt researchers create nanoscale slalom course for electrons: Professors from the Department of Physics and Astronomy have created a serpentine path for electrons November 27th, 2020

A new spin on atoms gives scientists a closer look at quantum weirdness October 30th, 2020

Superconductivity

A new candidate material for quantum spin liquids November 12th, 2020

New kind of superconductivity discovered: Researchers demonstrate a superconductor previously thought impossible November 6th, 2020

Govt.-Legislation/Regulation/Funding/Policy

New platform generates hybrid light-matter excitations in highly charged graphene December 2nd, 2020

CsPbBrI2 perovskites with low energy loss for high-performance indoor and outdoor photovoltaics December 1st, 2020

NIST sensor experts invent supercool mini thermometer November 17th, 2020

Arrowhead Interim Clinical Data Demonstrate ARO-AAT Treatment Improved Multiple Biomarkers of Alpha-1 Liver Disease November 13th, 2020

Possible Futures

Nanomaterials enable dual-mode heating and cooling device: Device could cut HVAC energy use by nearly 20% in the US December 2nd, 2020

Having it Both Ways: A Combined Strategy in Catalyst Design for Suzuki Cross-Couplings December 2nd, 2020

New platform generates hybrid light-matter excitations in highly charged graphene December 2nd, 2020

CsPbBrI2 perovskites with low energy loss for high-performance indoor and outdoor photovoltaics December 1st, 2020

Discoveries

No nanoparticle risks to humans found in field tests of spray sunscreens December 2nd, 2020

Nanomaterials enable dual-mode heating and cooling device: Device could cut HVAC energy use by nearly 20% in the US December 2nd, 2020

Having it Both Ways: A Combined Strategy in Catalyst Design for Suzuki Cross-Couplings December 2nd, 2020

New platform generates hybrid light-matter excitations in highly charged graphene December 2nd, 2020

Materials/Metamaterials

Quantum nanodiamonds may help detect disease earlier: The quantum sensing abilities of nanodiamonds can be used to improve the sensitivity of paper-based diagnostic tests, potentially allowing for earlier detection of diseases such as HIV, according to a study led by UCL research November 27th, 2020

One-way street for electrons: Scientists observe directed energy transport between neighbouring molecules in a nanomaterial November 27th, 2020

Staying ahead of the curve with 3D curved graphene November 20th, 2020

Manchester group discover new family of quasiparticles in graphene-based materials: Findings to help achieve Holy Grail of 2D materials - superfast electronic devices November 13th, 2020

Announcements

Nanomaterials enable dual-mode heating and cooling device: Device could cut HVAC energy use by nearly 20% in the US December 2nd, 2020

Having it Both Ways: A Combined Strategy in Catalyst Design for Suzuki Cross-Couplings December 2nd, 2020

The National Space Society Remembers Ben Bova : NSS Mourns the Loss of a Visionary NSS Leader December 2nd, 2020

Arrowhead Pharmaceuticals to Participate in Upcoming Conferences December 2nd, 2020

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

No nanoparticle risks to humans found in field tests of spray sunscreens December 2nd, 2020

Nanomaterials enable dual-mode heating and cooling device: Device could cut HVAC energy use by nearly 20% in the US December 2nd, 2020

Having it Both Ways: A Combined Strategy in Catalyst Design for Suzuki Cross-Couplings December 2nd, 2020

New platform generates hybrid light-matter excitations in highly charged graphene December 2nd, 2020

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

New platform generates hybrid light-matter excitations in highly charged graphene December 2nd, 2020

Graphenea awarded “Best Graphene Firm” prize October 20th, 2020

Revealing the reason behind jet formation at the tip of laser optical fiber October 16th, 2020

NSF renews Rice-based NEWT Center for water treatment: Partnership primed to introduce game-changing technologies to address global needs October 15th, 2020

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