three dimensional topological insulator is a fundamentally new phase electronic matter that is captured a
lot of interest and the condensed matter physics community over the past two or three
years
fundamental interest and three topological slayers
lies in the fact that exhibit a rare type behaviour called topological order
which describes organized movement of electrons the crystal
a consequence of this is that their surface electronics spectrums qualitatively distinct from any ordinary
material
in such a way is to allow us to select constant flow would not be
tracked by impurities
first experimental discovery but really talk much translator was making apply this that in and
money i think he has sounds group of princeton university falling really prediction by charles
cans collaborators at the university of pennsylvania
the prediction was based on the idea that pure and the money which is a
metal would become a topological insulator taken this newly formed into an insulator
outgoing edge when you would there's no
was predicted to perform this the defamation
to test for the topological slater phase the has a group search for the distinguishing
features of the serb select runs is a window into the box topological properties
in a general insulated with been or be coupling there can be seen or insert
states that standard log energy get is shown in this diagram
for an ordinary insulator these of the state always discourse such that they form even
number for me services
topological insulator however the number of surface form is services are
if even right count
is a topological distinction and it is clear that this method can only relies on
the material in a console
in this paper we address the question of whether they're experimental signatures the topological order
even in pure and to money
because it's money metallic surface take only relies on being able to separate surface reebok
states that the from the energy
the technique we need to do this is an angle result photo emission spectroscopy
the basic principles that photons intentional crystal bands money and excite electrons into the backing
by measuring the energy momentum these further we electrons the energy momentum dispersion inside the
crystal can be deduced
two measures then these energy and momentum analyzed electrons an accelerated towards the heavy scattering
target
where they will be preferential e scattered left to right based on there's interaction going
to standard scattering
the distinguishing properties of statistics are that there's and colourised and have no dispersion one
a direction normal to the surface
a typical for emission spectrum of an someone you shown here along momentum cut denoted
by the red line
if we look at how the state that for me energy change against bearing on
another one surface normal direction we find it only for right branches around zero momentum
show no dispersion
also find that these four ranges are still polarised proving that there indeed surfaced
there are two possible ways these service states comes first which reflect whether enter non-use
topological or not
if the word topological and the surface states as first in the sense shown in
the upper panel informant had a like for me services it on the right
if you were not topological the surface data disposition below and instead form a concentric
circular from is this
the dispersion certain states overall momentum space
we experimentally find that the from step is exhibited had a light all g which
confirms that and twenty the d topological
our here shows that even in metal there can be signatures a topological order
it also confirmed that topological properties of is intentionally three topological and sliders the right
from the electronic structure event
in future this procedure can be generally applied to search for her materials a topological
insulator