[Lex Computer & Tech Group/LCTG] Graphene

[Ted Kochanski]

No offense t the journalist -- but the person we want is a Prof in EECS
today he just got a major promotion at MIT

Tomás Palacios named new director of the Microsystems Technology
Laboratories
Palacios has served as director of the 6-A MEng Thesis Program, industry
officer, and professor of electrical engineering.
Jane Halpern | Meghan Melvin | Department of Electrical Engineering and
Computer Science | Microsystems Technology Laboratories
Publication Date:
December 15, 2022

here's the announcement for a talk he gave a couple of years ago in Germany
13. JANUARY 2020
<http://www.graphene.ac/index.php/2020/01/13/the-graphene-revolution-from-transistors-to-synthetic-cells-a-talk-by-prof-tomas-palacios-mit/>
 BY FEDERICA HAUPT <http://www.graphene.ac/index.php/author/haupt/>
The Graphene Revolution: From Transistors to Synthetic Cells – A talk by
Prof. Tomás Palacios (MIT)

On January 16, 2020, the Aachen Graphene & 2D Materials center will host a
seminar by Prof. Tomás Palacios, with the title “The Graphene Revolution:
>From Transistors to Synthetic Cells”.

Palacios is Professor of Electrical Engineering and Computer Science at the
Massachusetts Institute of Technology (MIT), as well as the founder and
director of the MIT MTL Center for Graphene Devices and 2D Systems, and
Chief Advisor and co-founder of Cambridge Electronics, Inc. His research
interests include the design, processing and characterization of new
electronic devices based on wide bandgap semiconductors and on
two-dimensional materials such as graphene, molybdenum disulfide (MoS2) and
tungsten diselenide (WSe2).  His work has been recognized with multiple
awards, including the Presidential Early Career Award for Scientists and
Engineers, the IEEE George Smith Award, and the NSF, ONR, and the DARPA
Young Faculty Awards.

In his talk, Palacios will review some of the recent progress on the use of
graphene and other two-dimensional materials for ultra-low power CMOS
circuits, sensors and large area devices for energy harvesting.  He will
also present a new generation of micro-systems that probe the limits of
electronics.
The other Prof deeply involved in Graphene particularly the so-called
"Magic Angle" layering of two Graphene Sheets is another young Spaniard at
MIT, Pablo Jarillo-Herrero, Cecil and Ida Green Professor of Physics
Best known for his groundbreaking research on twistronics.
and leader of the Jarillo-Herrero Group and Quantum Nanoelectronics @ MIT

recently Pablo Jarillo-Herrero received the Wolf Prize Laureate in Physics
2020 along with two of his "partners in the field"

The 2020 wolf prize in Physics is awarded to:  Pablo Jarillo-Herrero, Allan
H. MacDonald and Rafi Bistritzer.

Prof. Pablo Jarillo-Herrero
Massachusetts Institute of Technology – USA
“For pioneering theoretical and experimental work on twisted bilayer
graphene.”

Since the 2004 groundbreaking experiments regarding the two-dimensional
material -graphene, several research groups were soon studying the
properties of twisted bilayer graphene. Graphene is a significant
foundation for an entirely new generation of technologies. The hope is that
graphene-based applications will benefit the environment and reduce costs.
Electronic and computer industry requires materials whose conductance can
be controlled.

The work of Jarillo-Herrero, MacDonald and Bistrizer has shown that the
conductance properties of graphene interfaces can be controlled via the
spatial misfit angle between the layers and then at certain angles the
electrons exhibit surprising physical behavior. This physical discovery has
the potential of leading to an energy revolution.

In 2011, a group led by Allan Macdonald, a theoretical physicist from the
University of Texas, researched an intriguing behavior of twisted bilayer
graphene, where the atomic lattices of two stacked graphene layers are
laterally rotated with respect to each other by a small misfit angle.
According to the calculations of MacDonald and Bistrizer (who did his
post-doctoral thesis under the supervision of MacDonald at that time), the
tunneling velocity of electrons between the layers depends on the misfit
angle and completely vanishes at the “magic angle” of 1.1 degrees. It was
hoped that this discovery would lead to the creation of a new type of
super-conductor, namely a material that allows electrical current to pass
with no impedance and with no energy loss.

The original paper by MacDonald and Bistrizer, which describes their
discovery, was not received with enthusiasm by the scientific community and
was even forgotten for several years.

At the same time, Jarillo-Herrero was working on twisted bilayer graphene
in his lab at MIT. He became convinced that the ideas expressed by
Macdonald and Bistrizer had substance.
His research team  therefore invested considerable efforts in creating and
measuring twisted bilayer graphene of various twist angles. The experiments
proved successful in 2017 when it was found that positioning the layers at
an angle of 1.1 degrees relative to one another (“the magic angle”)
resulted in unusual electrical properties, precisely as MacDonald and
Bistrizer have suggested. In this position, at sufficiently low
temperatures, the electrons move from one layer to the other, creating a
lattice with unusual qualities. The paper that described the phenomenon,
which was published in Nature in 2018, revolutionized physics and triggered
a flood of additional papers.

The discovery opens the door to building a super-conductor from bilayer
graphene, in which electron movement is completely controlled by external
electrical current.

This electrical behavior resembles the behavior of copper-based
superconductors called Cuprates. Cuprates demonstrate electrical
conductivity with no resistance in relatively high temperatures compared
with other super-conductors. For this reason, Cuprates now form a source of
hope for realizing the dream of electrical conductivity with no energy loss
at temperatures close to room temperature. If this mission is achieved, it
would lead to a far-reaching energy revolution. However, one obstacle that
prevents this revolution is that we do not yet have a theory that explains
the behavior of superconductors at high temperatures. In the absence of a
solid theoretical foundation, it is difficult to develop new, better
materials. This is one of the reasons for the excitement around the
discovery of bilayer graphene and the magic angle, which allows us to
understand better what happens on the microscopic level when transitioning
from a conductor to a superconductor state.

Pablo Jarillo-Herrero (1976, Valencia) is an experimental condensed matter
physicist who works on quantum electronic transport and optoelectronics in
novel two-dimensional materials. His lab investigates their
superconducting, magnetic, and topological properties. Jarillo-Herrero
joined MIT in 2008 and was promoted to full professor in 2018. He received
his ”licenciatura” in physics from the University of Valencia in Spain, in
1999; a master of science degree from the University of California at San
Diego in 2001; and his PhD from the Delft University of Technology in the
Netherlands, in 2005.


Pablo Jarillo-Herrero could be on track for a Nobel Prize based on his work
with multiple layers of Graphene and other 2-D materials
 see for example

https://www.youtube.com/watch?v=O2HVCjhuJlE
Mar 14, 2018
Pablo Jarillo-Herrero (MIT) presents his surprising discovery of an
ultrathin material consisting of two misaligned sheets of graphene that can
be easily converted from being a Mott insulator to a superconductor at the
APS March Meeting 2018 in Los Angeles, CA.
-------------------------------------------------
Magic-Angle Graphene Superlattices: a New Platform for Strongly Correlated
Physics
APS Physics

27,041 views

-------------------------------------------------

In this talk I will discuss a new platform for strongly correlated physics
> based on magic-angle graphene superlattices. In particular, I will show
> that when two graphene sheets are twisted by an angle close to the
> theoretically predicted ‘magic angle’, the resulting flat band structure
> near the Dirac point gives rise to a strongly-correlated electronic system.
> These flat bands exhibit half-filling insulating phases at zero magnetic
> field, which we show to be a Mott-like insulator arising from electrons
> localized in the moiré superlattice. Doping away from the Mott-like state,
> we achieve electrically tunable superconductivity, with many
> characteristics similar to cuprate superconductivity, including
> superconducting domes, small Fermi pockets, and strong coupling.



   - or the Nature
   - NEWS FEATURE
   - 02 January 2019
   *How ‘magic angle’ graphene is stirring up physics*
   Misaligned stacks of the wonder material exhibit superconductivity and
   other curious properties.
   https://www.nature.com/articles/d41586-018-07848-2


   - Elizabeth Gibney
   <https://www.nature.com/articles/d41586-018-07848-2#author-0>

[image: Pablo Jarillo-Herrero, professor of physics, holding materials in
his lab at MIT]Overlapping two sheets of graphene shows a characteristic
pattern.Credit: Juliette Halsey for *Nature*

It was the closest that physicist Pablo Jarillo-Herrero had ever come to
being a rock star. When he stood up in March to give a talk in Los Angeles,
California, he saw scientists packed into every nook of the meeting room.
The organizers of the American Physical Society conference had to stream
the session to a huge adjacent space, where a standing-room-only crowd had
gathered. “I knew we had something very important,” he says, “but that was
pretty crazy.”

The throngs of physicists had come to hear how Jarillo-Herrero’s team at
the Massachusetts Institute of Technology (MIT) in Cambridge had unearthed
exotic behaviour in single-atom-thick layers of carbon, known as graphene.
Researchers already knew that this wonder material can conduct electricity
at ultra-high speed
<https://www.nature.com/news/graphene-conducts-electricity-ten-times-better-than-expected-1.14676>.
But the MIT team had taken a giant leap by turning graphene into a
superconductor: a material that allows electricity to flow without
resistance. They achieved that feat by placing one sheet of graphene over
another, rotating the other sheet to a special orientation, or ‘magic
angle’, and cooling the ensemble to a fraction of a degree above absolute
zero. That twist radically changed the bilayer’s properties — turning it
first into an insulator and then, with the application of a stronger
electric field, into a superconductor.

Ted

On Thu, Dec 15, 2022 at 10:17 PM Charles Holbrow <chholbrow at gmail.com>
wrote:

> Dan Kleppner has spoken with Maia Weinstock who is a science writer and
> Associate Director at MIT News.  She is author of a recent biography of
> Millie Dresselhaus (1930-2017).  Its title *Carbon Queen *recognizes
> Millie's important work on carbon nanotubes.  Ms. Weinstock lives in
> Belmont and says she's willing to talk to us but wants to speak to a live
> audience.
>
> Have any of us read her book?
>
> Can we provide a big enough --- say 20 --- live audience so that LCTG is
> not embarrassed?  The current 5 to 7 live audience would be embarrassingly
> small.
>
> Work on layers of graphene two and three sheets thick and rotated small
> angles with respect to each other has found superconductivity and other
> surprising electronic effects.  The studies of graphene are producing
> exciting discoveries.
>
> --Charlie
>
> On Thu, Dec 15, 2022 at 1:31 PM john rudy <jjrudy1 at comcast.net> wrote:
>
>> Do we have a metallurgist in the group (or one with a contact) who could
>> give us a talk on graphene?
>>
>> John
>>
>>
>>
>> John Rudy
>>
>> 781-861-0402
>>
>> 781-718-8334 (cell)
>>
>> John.rudy at alum.mit.edu
>>
>>
>>
>> 13 Hawthorne Lane
>>
>> Bedford, MA  01730-1047
>>
>>
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