Science AMA Series: The discovery of a new particle called Weyl
challenged our understanding of quantum field theory and was one of the
Physics World’s 2015 Breakthroughs of the year. Mazhar Ali is her
Abstract
My name is Mazhar Ali and I am a researcher with the Max PIank Institute
for Microstructure Physics in Halle, Germany and also at IBM in San
Jose, California. Before that I was at Princeton where many of us worked
on and discovered some of the first Dirac and Weyl materials, including
the first “type II” Weyl semimetal, WTe2, which was on the frontpage
of r/science last week. Dirac and Weyl materials are a super hot topic
in condensed matter physics right now, but has branched out and captured
the attention of chemists, particle physicists, materials scientists,
electrical engineers and more! These materials host massless dirac
electrons (similar to graphene) and so can have “light-like” electrons
moving at extremeley high mobilities! Recently, people have been able to
use the intracies of the electronic structure of a material to massage
these massless dirac electrons into becoming Weyl electrons; still
massless, but with the added bonus of having spin up and spin down be
energetically different! We will see in the near future what we can do
with these new particles, but first we need to understand everything
better. Out of the 3 camps of Fermions (Weyl, Dirac, and Majorana) we
had previously only realized Dirac fermions in real life. Now we have
realized the 2nd camp, Weyl! Majorana might be just around the corner
too! It is a very exciting time to be involved! I am here to answer any
questions you all might have about Dirac and Weyl materials, physics,
chemistry, etc! Or, if you just want to know about solid state and
materials chemistry, AMA! A few links to a few of the relevant papers
(obviously there are loads more): Titanic Magnetoresistance in WTe2:
http://www.nature.com/nature/journal/v514/n7521/full/nature13763.html
Type II Weyl Semimetals:
http://www.nature.com/nature/journal/v527/n7579/full/nature15768.html
Cd3As2, a Dirac Semimetal:
http://www.nature.com/nmat/journal/v13/n7/full/nmat3990.html Ultrahigh
electron mobility in Cd3As2:
http://www.nature.com/nmat/journal/v14/n3/full/nmat4143.html Type I Weyl
Semimetal (open access):
http://journals.aps.org/prx/abstract/10.1103/PhysRevX.5.031013 A very
nice viewpoint on Weyl electrons by Leon Balents (professor at UCSB):
http://physics.aps.org/articles/v4/36 open access, arXiv versions of
most of the above articles can be found through google fairly easily as
well. I will be back at 2 pm EST (11 am PST, 7 pm UTC) to answer your
questions, ask me anything! EDIT: I am back! May go for lunch in about
an hour, but then will be back again after! EDIT 2: Hey all! Gonna take
a lunch break, be back in about an hour or so! (Currently 12:20 PST)
EDIT 3: Back again!