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Expanding the Use of Silicon in Batteries, By Preventing Electrodes From Expanding

Posted By Graphene Council, The Graphene Council, Tuesday, March 26, 2019
The latest lithium-ion batteries on the market are likely to extend the charge-to-charge life of phones and electric cars by as much as 40 percent. This leap forward, which comes after more than a decade of incremental improvements, is happening because developers replaced the battery’s graphite anode with one made from silicon. Research from Drexel University and Trinity College in Ireland now suggests that an even greater improvement could be in line if the silicon is fortified with a special type of material called MXene.

This adjustment could extend the life of Li-ion batteries as much as five times, the group recently reported in Nature Communications. It’s possible because of the two-dimensional MXene material’s ability to prevent the silicon anode from expanding to its breaking point during charging — a problem that’s prevented its use for some time.

Silicon anodes are projected to replace graphite anodes in Li-ion batteries with a huge impact on the amount of energy stored,” said Yury Gogotsi, PhD, Distinguished University and Bach Professor in Drexel’s College of Engineering and director of the A.J. Drexel Nanomaterials Institute in the Department of Materials Science and Engineering, who was a co-author of the research. “We’ve discovered adding MXene materials to the silicon anodes can stabilize them enough to actually be used in batteries.”

In batteries, charge is held in electrodes — the cathode and anode — and delivered to our devices as ions travel from anode to cathode. The ions return to the anode when the battery is recharged. Battery life has steadily been increased by finding ways to improve the electrodes’ ability to send and receive more ions. Substituting silicon for graphite as the primary material in the Li-ion anode would improve its capacity for taking in ions because each silicon atom can accept up to four lithium ions, while in graphite anodes, six carbon atoms take in just one lithium. But as it charges, silicon also expands — as much as 300 percent — which can cause it to break and the battery to malfunction.

Most solutions to this problem have involved adding carbon materials and polymer binders to create a framework to contain the silicon. The process for doing it, according to Gogotsi, is complex and carbon contributes little to charge storage by the battery.

By contrast, the Drexel and Trinity group’s method mixes silicon powder into a MXene solution to create a hybrid silicon-MXene anode. MXene nanosheets distribute randomly and form a continuous network while wrapping around the silicon particles, thus acting as conductive additive and binder at the same time. It’s the MXene framework that also imposes order on ions as they arrive and prevents the anode from expanding.

“MXenes are the key to helping silicon reach its potential in batteries,” Gogotsi said. “Because MXenes are two-dimensional materials, there is more room for the ions in the anode and they can move more quickly into it — thus improving both capacity and conductivity of the electrode. They also have excellent mechanical strength, so silicon-MXene anodes are also quite durable up to 450 microns thickness.”

MXenes, which were first discovered at Drexel in 2011, are made by chemically etching a layered ceramic material called a MAX phase, to remove a set of chemically-related layers, leaving a stack of two-dimensional flakes. Researchers have produced more than 30 types of MXene to date, each with a slightly different set of properties. The group selected two of them to make the silicon-MXene anodes tested for the paper: titanium carbide and titanium carbonitride. They also tested battery anodes made from graphene-wrapped silicon nanoparticles.

All three anode samples showed higher lithium-ion capacity than current graphite or silicon-carbon anodes used in Li-ion batteries and superior conductivity — on the order of 100 to 1,000 times higher than conventional silicon anodes, when MXene is added.

“The continuous network of MXene nanosheets not only provides sufficient electrical conductivity and free space for accommodating the volume change but also well resolves the mechanical instability of Si,” they write.  “Therefore, the combination of viscous MXene ink and high-capacity Si demonstrated here offers a powerful technique to construct advanced nanostructures with exceptional performance.”

Chuanfang Zhang, PhD, a post-doctoral researcher at Trinity and lead author of the study, also notes that the production of the MXene anodes, by slurry-casting, is easily scalable for mass production of anodes of any size, which means they could make their way into batteries that power just about any of our devices.

“Considering that more than 30 MXenes are already reported, with more predicted to exist, there is certainly much room for further improving the electrochemical performance of battery electrodes by utilizing other materials from the large MXene family,” he said.

Tags:  Batteries  Battery  Chuanfang Zhang  Drexel University  Graphene  Li-ion batteries  Trinity College in Ireland  Yury Gogotsi 

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How is graphene holding up at Warsaw University of Technology?

Posted By Graphene Council, The Graphene Council, Tuesday, March 26, 2019
Updated: Tuesday, March 26, 2019

Warsaw University of Technology (“WUT”), for more than 10 years, has been involved in extensive research into graphene, its applications and production techniques, in both domestic and international projects (it boasts more than 250 scientific publications in international journals and several patents). As the only institution of higher education in Poland, it is a member of the Graphene Flagship programme, the EU’s biggest ever research initiative. The project work is carried out among others in the cutting-edge Center for Advanced Materials and Technologies (CEZAMAT) and is scheduled to continue until at least March 2022.

The University cooperates with scientific and industrial partners from Sweden, the United Kingdom, Austria and China to further advance the technology of epitaxial graphene on silicon carbide for applications such as 5G technologies. WUT’s PhD students engage in joint research at scientific institutions across Europe, including Cambridge and Madrid.

WUT pursues a number of high-end national projects that focus on research into graphene and new two-dimensional materials: Team-Tech (Foundation for Polish Science), Lider and TechmatStrateg (National Centre for Research and Development), Sonata and Preludium (National Science Centre), Diamentowy Grant (Ministry of Science and Higher Education).

The University has established the Graphene Laboratory (Faculty of Chemistry and Process Engineering) dedicated to the carbon nanomaterial production, characterization and exploration of new applications, e.g. hybrid fluorescent materials or infrared radiation absorbers or even some unusual solutions such as the development of new polyester gelcoats to be used in the construction of new generation yachts, Delphia Nano Solution. It is also a promoter of spin-offs aimed at the transfer of graphene technologies and applications to industry and putting them to use for commercial production. Moreover, numerous businesses collaborate with Warsaw University of Technology in application research under joint projects and bilateral agreements.

The work on graphene at Warsaw University of Technology covers two types of this material: graphene flakes and epitaxial graphene (film). “The University has several processing lines producing graphene flakes with the use of both chemical methods of oxidation and reduction of graphene oxide and the so-called liquid-phase direct exfoliation method. Last year, a new method was launched for the production of graphene flakes which is cheap, green and easily scalable for industry. WUT is now in the process of patenting this new technology,” says Prof. Mariusz Zdrojek, head of the graphene research group at  WUT’s Faculty of Physics.

The University has also launched an epitaxial graphene growth (on copper foil) for the purpose of its own application research. Moreover, it has developed and launched the growth technique of new two-dimensional materials in the graphene family, MXenes. The synthesis of other two-dimensional materials, i.e. molybdenum disulfide (MoS2), using the epitaxial growth method has also been elaborated.

Some of the more exciting graphene applications developed by the Warsaw University of Technology in collaboration with the Polish industry include:

- New generation ultrafast infrared photodetector created in 2015 under the Graf-Tech project. The device, in which graphene plays a key role, is in the pre-implementation phase (Faculty of Physics);

- Electronic nanodevices to be used in high-frequency electronics (for fast detectors, sensors or diodes), a product of the Lider project. Currently, work is underway on the patent application (Faculty of Physics);

- New nanocomposites for electromagnetic radiation protection for cybersecurity, electronics, aerospace and 5G technology. The patent application is pending with the European Patent Office (Faculty of Physics);

- Graphene thermal pastes for electronics as novel materials for heat transfer. Conductive graphene inks and pastes suitable for multi-surface printing technologies (e.g. clothes or banknote printing), where they act as transparent electrodes. Patented technology (Faculty of Mechatronics);

- Membrane technologies for mobile drinking water treatment plants, where use of graphene has improved selectivity. (Faculty of - Material Science and Engineering; Faculty of Chemical and Process Engineering);

- Graphene as an anti-corrosion coating, a product of the GrafTech project as part of the joint effort with a research partner (Faculty of Physics);

- other, i.e. flexible displays, pressure sensors, glucose sensors or amino acid biosensors.

For the past few years WUT’s researchers have been also conducting research into the application of other 2D materials. This  has resulted in creation of the materials’ potential new applications eg in the production of composites for the space and aerospace industries or as an innovative platform for drug delivery, new optoelectronic nanodevices or devices for terahertz electronics applications.

With the appropriate know-how, materials and infrastructure and access to the country’s best specialists,  Warsaw University of Technology remains at the leading edge of the development of technologies and applications for other two-dimensional materials, considered to be of strategic importance to advanced industry sectors.

Tags:  2D materials  Graphene  Graphene Flagship  Mariusz Zdrojek  Warsaw University of Technology 

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Graphene and silk make self-healable electronic tattoos

Posted By Graphene Council, The Graphene Council, Tuesday, March 26, 2019
Updated: Tuesday, March 26, 2019
Researchers have designed graphene-based e-tattoos designed to act as biosensors. The sensors can collect data relate to human health, such as skin reactions to medication or to assess the degree of exposure to ultraviolet light.

Considerable research has gone into electronic tattoos (or e-tattoos), as part of the emerging field of or epidermal electronics. These are a thin form of wearable electronics, designed to be fitted to the skin. The aim of these lightweight sensors is to collect physiological data through sensors.

The types of applications of the sensors, from Tsinghua University, include assessing exposure to ultraviolet light to the skin (where the e-tattoos function as dosimeters) and for the collection of ‘vital signs’ to assess overall health or reaction to a particular medication (biosensors).

The use of graphene aids the collection of electric signals and it also imparts material properties to the sensors, allowing them to be bent, pressed, and twisted without any loss to sensors functionality.

The new sensors, developed in China, have shown – via as series of tests – good sensitivity to external stimuli like strain, humidity, and temperature. The basis of the sensor is a material matrix composed of a graphene and silk fibroin combination.

The highly flexible e‐tattoos are manufactured by printing a suspension of graphene, calcium ions and silk fibroin. Through this process the graphene flakes distributed in the matrix form an electrically conductive path. The path is highly responsive to environmental changes and it can detect multi-stimuli.

The e‐tattoo is also capable of self-healing. The tests showed how the tattoo heals after damage by water. This occurs due to the reformation of hydrogen and coordination bonds at the point of any fracture. The healing efficiency was demonstrated to be 100 percent and it take place in less than one second.

The researchers are of the view that the e-tattoos can be used as electrocardiograms, for assessing breathing, and for monitoring temperature changes. This means that the e‐tattoo model could be the basis for a new generation of epidermal electronics.

Commenting on the research, chief scientist Yingying Zhang said: “Based on the superior capabilities of our e-tattoos, we believe that such skin-like devices hold great promise for manufacturing cost-effective artificial skins and wearable electronics.”

Tags:  biosensors  Electronics  Graphene  Healthcare  Tsinghua University  Yingying Zhang 

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Andrey Turchanin Elected Partnering Division Leader

Posted By Graphene Council, The Graphene Council, Monday, March 25, 2019
Updated: Thursday, March 21, 2019
Andrey Turchanin from Friedrich Schiller University Jena (Germany) and Yuri Svirko from University of Eastern Finland have been appointed by the Graphene Flagship Executive Board as the new leader and deputy, respectively, of the Graphene Flagship Partnering Division. The vote took place in November and, altogether, 39 Associated Members' representatives voted (43.6%). Andrey Turchanin received 21 votes (53.85%) and Yuri Svirko received 18 votes (46.15%). 

The primary responsibilities of the Graphene Flagship Partnering Division are to improve cooperation through the identification of opportunities for various types of synergies between Core partners, Partnering Projects (PPs) and Associated Members (AMs), and to provide recommendations on the partnering mechanism to the Graphene Flagship management and other relevant stakeholders based on the feedback and direct interactions with the Partnering Division members. They will gather feedback from Partnering Division members on a regular basis on their needs and challenges in engaging in collaborations with the Graphene Flagship. 

Andrey Turchanin is Head of the Laboratory of Applied Physical Chemistry & Molecular Nanotechnology at the Friedrich Schiller University Jena. With broad and long-term experience of more than ten years in graphene and related 2D materials for academic research and industrial applications, he was coordinator of the project "Graphene Nanomembranes from Molecular Monolayers" at the Graphene Flagship Open Call from 2014 to 2016. He was also a member of Work Package Enabling Materials and Work Package Flexible Electronics in the Graphene Flagship Core 1 Project from 2016 to 2018. In the FLAG-ERA Joint Transnational Call 2017, he is coordinator of the H2O ("Heterostructures of 2D Materials and Organic Semiconductor Nanolayers") Partnering Project. 

"The Partnering Projects, with their complementary expertise, bring great added value to the Graphene Flagship´s scientific community enabling new possibilities both in research and in industrial implementation of graphene and related 2D materials," says Turchanin 

Yuri Svirko is a physics prrofessor at the Department of Physics and Mathematics at the University of Eastern Finland (UEF). He was the principal investigator on the UEF team, which was involved in the Graphene Flagship ramp up phase and Core 1, therefore he has experience working both as a partner and as an Associate Member of the Flagship. He is an internationally recognized expert in the field of graphene science, with wide experience in EU and national projects focused on the fabrication of micro and nanoscale optical components, among others. Yuri Svirko is also the principal investigator of the CoExAN Partnering Project "Collective Excitations in Advanced Nanostructures".

The Support of the SCOPE Project to the GF Partnering Division

The SCOPE project, funded by the European Commission, provides support to institutions and researchers involved in Graphene Flagship Partnering Projects (PPs) and Associated Members (AMs) by granting several types of grants to help them integrate with the Graphene Flagship Core projects. Communication of research results is also offered via news articles and dissemination in social media. 

The Graphene Flagship Partnering Division is also supported by the SCOPE travel grants that make the attendance of their members to the governance meetings of the Graphene Flagship posible. Andrey Turchanin is also a member of the SCOPE  Advisory Committee.  

Tags:  2D materials  Andrey Turchanin  Friedrich Schiller University Jena  Graphene  The Graphene Flagship  University of Eastern Finland  Yuri Svirko 

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Graphene@Manchester at The University of Manchester

Posted By Graphene Council, The Graphene Council, Monday, March 25, 2019
Updated: Thursday, March 21, 2019

Graphene@Manchester at The University of Manchester is an on-going programme of activity to ensure that Manchester and the UK play a leading international role in developing the revolutionary potential of graphene.

Graphene@Manchester is creating a critical mass of graphene and 2D materials expertise made up of scientists, manufacturers, engineers, innovators, investors and industrialists to build a thriving knowledge-based economy.   

At the heart the vision is the National Graphene Institute and the Graphene Engineering Innovation Centre (GEIC), multi-million pound facilities with a commitment fostering strong industry-academic collaborations.   

The Graphene Council is a proud founding Affiliate Member of the GEIC, providing access to a word class facility and the graphene experts at the University of Manchester. 

Graphene@Manchester is home to an unrivalled breadth of expertise across 30 academic groups. This expertise gives us the ability to take graphene applications from basic research to finished product.   

Graphene is a disruptive technology; one that could open up new markets and even replace existing technologies or materials. From transport, medicine, electronics, energy, and water filtration, the range of industries where graphene research is making an impact is substantial.   

Graphene has the potential to create the next-generation of electronics currently limited to science fiction. Our facilities provide dedicated equipment to develop and produce inks and formulations for printed and flexible electronics, wearables and coatings.

Tags:  2D materials  coatings  Graphene  University of Manchester 

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Strategic Insight Paper Explores Graphene's Impact

Posted By Graphene Council, The Graphene Council, Monday, March 25, 2019
Updated: Thursday, March 21, 2019
The International Sign Association (ISA)  is marking its 75th anniversary by giving back to the sign, graphics and visual communications industry. A series of white papers will explore future technologies expected to impact the industry.

The first Strategic Insight paper, Nanomaterials: Giant Changes Coming from the Tiniest of Materials, was written by Dexter Johnson, senior science editor/analyst for the Graphene Council. It explores nanomaterials and their potential uses in protective applications, thin-film electronics (i.e. flexible displays and electronics), digital displays, pigments for inks and paper.

"ISA was founded in 1944 by visionaries who wanted to see how they could grow the industry and their businesses," said Lori Anderson, ISA president and CEO. "As we mark the 75th anniversary, it only seems fitting that we honor their legacy by looking forward as well. These Strategic Insight papers, written by leading thinkers from inside and outside our industry, will help companies explore the next iteration of the sign, graphics and visual communications industry in a way that honors our founders."

Tags:  Graphene  International Sign Association  nanomaterials  The Graphene Council 

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Micro and nano materials, including clothing for Olympic athletes

Posted By Graphene Council, The Graphene Council, Monday, March 25, 2019
Updated: Monday, March 25, 2019
A research team of materials engineers and performance scientists at Swansea University has been awarded £1.8 million to develop new products - in areas from the motor industry to packaging and sport - that make use of micro and nano materials based on specialist inks.

One application already being developed is specialist clothing that will be worn by elite British athletes in training and at the 2020 Olympic and Paralympic Games.

The researchers will be incorporating advanced materials such as graphene into flexible coatings which will be printed and embedded into bespoke garments to enhance the performance of elite athletes.

The purpose of the project is to serve as a pipeline for new ideas, testing to see which of them can work in practice and on a large scale, and then turning them into actual products.

The gap between initial concept and final product is known in manufacturing as the "valley of death" as so many good ideas simply fail to make it. The pipeline will help ensure more of them make it across the valley: off the drawing board and into production.

This project is unique in that it is driven by market requirements. As well as the wearable technology, identified by the English Institute of Sport (EIS), two other areas will be amongst the first to use the pipeline: SMART packaging, with the company Tectonic, and the car industry, with GTS Flexible Materials

The project is a collaboration between two teams in Swansea University's College of Engineering: the Welsh Centre for Printing and Coating (WCPC) led by Professor Tim Claypole and Professor David Gethin, and the Elite and Professional Sport (EPS) research group, namely Dr Neil Bezodis, Professor Liam Kilduff and Dr Camilla Knight.

The WCPC is pioneering ways of using printing with specialist inks as an advanced manufacturing process. Their expertise will be central to the project.

Professor Tim Claypole, Director of the Wales Centre for Printing and Coating, said:

"The WCPC expertise in ink formulation and printing is enabling the creation of a range of advanced products for a wide range of applications that utilise innovative materials".

Sport, which is one of the areas the project covers, has been a test bed for technology before. For example, heart rate monitors and exercise bikes have now become mainstream.

EPS project lead Dr Neil Bezodis underlined the importance of links with partners within the overall project:

"Collaborations between industrial partners which are driven by end users in elite sport are key to ensuring our research has a real impact".

Tags:  Camilla Knight  coatings  David Gethin  Graphene  Liam Kilduff  nanomaterials  Neil Bezodis  sporting goods  Swansea University  Tim Claypole  Welsh Centre for Printing and Coating 

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Talga Anode Achieves Outstanding Freezing Temperature Performance

Posted By Graphene Council, The Graphene Council, Saturday, March 23, 2019
Talga Resources , ispleased to announce outstanding low temperature test results from its engineered graphite anode product for lithium-ion batteries, Talnode™-C.

Development of Talnode-C is accelerating through rigorous commercial validation processes at multiple commercial partner facilities and independent battery institutes in Asia, USA and Europe. In new tests conducted at a leading Japanese battery institute, Li-ion batteries using Talnode-C were subjected to performance tests under a range of temperatures including freezing conditions. Highlights of the test results include:
• Retention of 100% capacity and 100% cycle efficiency at freezing temperature (0°C)
• Out-performance of market leading commercial anode products

In freezing conditions Li-ion batteries usually suffer lower capacity retention and cycling efficiency, causing shorter run time of devices such as laptop computers and mobile phones, or shorter driving range of electric vehicles. Cold temperatures can also cause deposits of lithium metal to form in the battery, causing internal short circuits that can lead to fire in the cell, making low temperature performance a critical technical deliverable for Li-ion batteries1.

Talga Managing Director, Mr Mark Thompson: “These results show Talnode-C has the potential to solve problems that have long challenged Li-ion batteries in cold weather applications, where conventional graphite anodes struggle or fail to perform. This is a further demonstration that Talga’s anode products made from our high grade graphite deposit in Sweden, using wholly owned process and refining technology, have exciting potential in the fast growing Li-ion battery market.”

Moving Forward
Market validation of the TalnodeTM product range, and in particular the flagship Li-ion anode product Talnode-C, continues as Talga works to incorporate the development of its new class of high-performance graphitic carbon anode products into its long-term business strategy.

Advanced testing and validation, including the surface treatment and coating of Talnode-C, progresses across multiple commercial partner facilities and independent battery institutes in Asia, USA and Europe. It is expected that Talnode-C, a fully engineered and formulated active anodeready product to be marketed directly towards Li-ion battery manufacturers, will form the
foundation of a near-term commercialisation opportunity for the Company’s larger scale development of the Vittangi graphite project in Sweden.

Low Temperature Technical Background
Li-ion batteries are widely used at room temperature because of their high specific energy and energy density, long cycle life, low self-discharge, and long shelf life2. When charging a Li-ion battery, the lithium ions inside the battery are soaked up (as in a sponge) by the porous negative electrode (anode), made of graphite.

Under temperatures approaching freezing (0°C) however, the lithium ions aren’t efficiently captured by the anode. Instead, many lithium ions are reduced to lithium metal and coat the surface of the anode, a process called lithium plating, resulting in less lithium available to carry the flow of electricity. Consequently, the battery’s capacity and cycle efficiency drops and this translates to poorer performance3.

In cooler countries of the northern hemisphere, it has been measured that the driving range of electric vehicles can be reduced by 41% in real world sub-zero conditions4. The most significant negative effect of low temperature on Li-ion batteries is the generation of lithium metal growths called dendrites, which can perforate the separator and cause a short circuit or fire in the lithium-ion cells. A highly visible example of this was in the 2013 grounding of Boeing 787 Dreamliner aircraft following a spate of electrical system failures, including fires. Investigation found that cold winter overnight temperatures fostered lithium plating within the battery cells and caused the short circuits5.

Tags:  Graphene  Li-ion batteries  Mark Thompson  Talga Resources 

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Versarien PLC - USA Update

Posted By Graphene Council, The Graphene Council, Saturday, March 23, 2019
Versarien plc, is pleased to provide an update on the Company's activities in the United States of America. Versarien has recently established a new US corporate entity, Versarien Graphene Inc, to facilitate the Company's graphene and other 2D materials activities in the USA.  The Company is additionally in the process of establishing a new office, laboratory facility and applications centre in Houston, Texas that will act as a hub for the Company's activities in North America.

Patrick Abbott has been appointed as Versarien's Vice President North American Operations to oversee these activities and he will be based at the Company's Houston facility once established.  Patrick is an experienced speciality materials professional with over 20 years' experience in the sector.  

He is a former US Marine Corps Officer who spent over 16 years in a variety of global business development and marketing roles at BASF. In 2015 and 2016, Patrick was part of the team transitioning specific product lines to Huntsman Corporation. Subsequently he established Global Marketing Empire Solutions, a disruptive technology consulting company and joined XG Sciences, a company focussed on graphene nano technology, as their global sales manager.  At XG Sciences he was tasked with assisting the executive team in transitioning the company from an academic company to full commercialisation.

The establishment of this US presence follows on from collaboration with partners in the region.  Further North American potential collaboration partners and customers have been identified, both through inbound enquires and proactive approaches, and it is intended that the Houston facility and additional resource will enable these to be more efficiently progressed.

The Company is pleased to be participating in the UK Government organised "UK Technology and Capability Showcase" being held at Collins Aerospace in Charlotte, North Carolina, on 25 March 2019 where the Company will be presenting its 2D materials technology to Collins Aerospace representatives.

Neill Ricketts, CEO of Versarien, commented: "We are very pleased to be moving to the next stage of our development in the US with the establishment of Versarien Graphene Inc and a dedicated facility in Houston. 

"We are already pursuing a number of substantial opportunities in the US and I expect our level of activity to significantly increase in the coming months, particularly given the high number of enquires we have had for the supply of our graphene and other 2D materials from leading US companies."

"I am also particularly pleased we have secured the services of Patrick Abbott and I would like to formally welcome him to the Versarien team.  His skills and experience will be invaluable as we look to build more relationships and commercialise graphene enhanced products with US companies."

"Coupled with the recent progress we have made in China and elsewhere we remain confident that we can make further rapid progress this year.  I look forward to providing further updates on our US and other activities in due course."

Tags:  2D materials  Graphene  Neill Ricketts  Patrick Abbott  Versarien 

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A quantum magnet with a topological twist

Posted By Graphene Council, The Graphene Council, Tuesday, March 19, 2019
Updated: Tuesday, March 19, 2019
Taking their name from an intricate Japanese basket pattern, kagome magnets are thought to have electronic properties that could be valuable for future quantum devices and applications. Theories predict that some electrons in these materials have exotic, so-called topological behaviors and others behave somewhat like graphene, another material prized for its potential for new types of electronics.

Now, an international team led by researchers at Princeton University has observed that some of the electrons in these magnets behave collectively, like an almost infinitely massive electron that is strangely magnetic, rather than like individual particles. The study was published in the journal Nature Physics this week.

The team also showed that placing the kagome magnet in a high magnetic field causes the direction of magnetism to reverse. This "negative magnetism" is akin to having a compass that points south instead of north, or a refrigerator magnet that suddenly refuses to stick.

"We have been searching for super-massive 'flat-band' electrons that can still conduct electricity for a long time, and finally we have found them," said M. Zahid Hasan, the Eugene Higgins Professor of Physics at Princeton University, who led the team. "In this system, we also found that due to an internal quantum phase effect, some electrons line up opposite to the magnetic field, producing negative magnetism."

The team explored how atoms arranged in a kagome pattern in a crystal give rise to strange electronic properties that can have real-world benefits, such as superconductivity, which allows electricity to flow without loss as heat, or magnetism that can be controlled at the quantum level for use in future electronics.

The researchers used state-of-the-art scanning tunneling microscopy and spectroscopy (STM/S) to look at the behavior of electrons in a kagome-patterned crystal made from cobalt and tin, sandwiched between two layers of sulfur atoms, which are further sandwiched between two layers of tin.

In the kagome layer, the cobalt atoms form triangles around a hexagon with a tin atom in the center. This geometry forces the electrons into some uncomfortable positions -- leading this type of material to be called a "frustrated magnet."

To explore the electron behavior in this structure, the researchers nicked the top layers to reveal the kagome layer beneath.

They then used the STM/S technique to detect each electron's energy profile, or band structure. The band structure describes the range of energies an electron can have within a crystal, and explains, for example, why some materials conduct electricity and others are insulators. The researchers found that some of electrons in the kagome layer have a band structure that, rather than being curved as in most materials, is flat.

A flat band structure indicates that the electrons have an effective mass that is so large as to be almost infinite. In such a state, the particles act collectively rather than as individual particles.

Theories have long predicted that the kagome pattern would create a flat band structure, but this study is the first experimental detection of a flat band electron in such a system.

One of the general predictions that follows is that a material with a flat band may exhibit negative magnetism.

Indeed, in the current study, when the researchers applied a strong magnetic field, some of the kagome magnet's electrons pointed in the opposite direction.

"Whether the field was applied up or down, the electrons' energy flipped in the same direction, that was the first thing that was strange in terms of the experiments," said Songtian Sonia Zhang, a graduate student in physics and one of three co-first-authors on the paper.

"That puzzled us for about three months," said Jia-Xin Yin, a postdoctoral research associate and another co-first author on the study. "We were searching for the reason, and with our collaborators we realized that this was the first experimental evidence that this flat band peak in the kagome lattice has a negative magnetic moment."

The researchers found that the negative magnetism arises due to the relationship between the kagome flat band, a quantum phenomenon called spin-orbit coupling, magnetism and a quantum factor called the Berry curvature field. Spin-orbit coupling refers to a situation where an electron's spin, which itself is a quantum property of electrons, becomes linked to the electron's orbital rotation. The combination of spin-orbital coupling and the magnetic nature of the material leads all the electrons to behave in lock step, like a giant single particle.

Another intriguing behavior that arises from the tightly coupled spin-orbit interactions is the emergence of topological behaviors. The subject of the 2016 Nobel Prize in Physics, topological materials can have electrons that flow without resistance on their surfaces and are an active area of research. The cobalt-tin-sulfur material is an example of a topological system.

Two-dimensional patterned lattices can have other desirable types of electron conductance. For example, graphene is a pattern of carbon atoms that has generated considerable interest for its electronic applications over the past two decades. The kagome lattice's band structure gives rise to electrons that behave similarly to those in graphene.

Tags:  Graphene  M. Zahid Hasan  Princeton University  Songtian Sonia Zhang 

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