PhD and (master) internship
proposal on the strontium
Quantum magnetism of
ultracold fermions in optical lattices
We offer an experimental internship in the field of
ultracold atoms. Our research theme is quantum magnetism, i.e.,
the collective behavior of ensembles of interacting
spin-carrying particles. Our
experiment produces degenerate gases of fermionic strontium 87
atoms, that are then arranged on a periodic structure created by
interfering laser beams: an optical lattice potential. Our
system realizes the antiferromagnetic Heisenberg Hamiltonian.
Our aim is to study the conditions for the
emergence of antiferromagnetic ordering. We can realize
situations analogous to those encountered by electrons (of spin
˝) in crystalline materials, but also situations that strongly
contrast with those, as a consequence of the spin 9/2 of our
atomic species. These systems appear promising to create novel
magnetic phases, such as spin liquids, with connections with
topological materials and exotic forms of superfluidity.
Presently, we are implementing protocols that exploit the narrow
lines of strontium (of use e.g. to atomic clocks) to
deterministically prepare low-energy spin textures and study
their dynamics and correlations.
The work plan is as follows:
- The intern will be responsible for characterizing
on the atoms a high-resolution imaging system (~1.2 µm),
projecting onto a high-end, ultra-low-noise S-CMOS camera. The
optical system has been built and characterized on an optical
bench last year, and must now be moved on top of the vacuum
cell. Figures of merit are optical resolution on the actual
atomic cloud on the one hand, and detectivity on the other one –
our expectation being close to single atom detectivity.
- Depending on progresses, the intern will
participate in our protocols for preparing and evolving
low-energy spin textures. The response of the sample to these
manipulations, e.g. their degree of reversibility, will provide
insight into the low-energy magnetic properties of the system.
In the context of our collaboration with the team of T.
Roscilde, ENS Lyon, we are developing observables for evidencing
The project is built in strong connection with a
second experiment in our group (quantum magnetism with dipolar
chromium atoms), and theory activities in our group (P. Pedri)
and at ENS Lyon (T. Roscilde). The internship will provide an
introduction to the essential experimental tools of cold atom
experiments (lasers, optics, optomechanics, electronics), and
will include a large part of team work on the ultracold atom
This work may act as an introduction to a PhD
thesis on the Sr experiment. As of October 2021, this project
involves two PhD students (1st-year and 3rd
year), and two permanent CNRS researchers.
Contact: Martin Robert de Saint Vincent, Bruno
PhD and Internship proposal on the Superradiant laser experiment
offer an experimental internship in the field of atomic physics.
Our proposal is in the context of a new experiment under
development in our group, that aims at harvesting the phenomenon
of superradiance to produce a new kind of coherent light source.
Remarkably, the frequency stability and narrow linewidth of this
light source, named “super-radiant laser”, makes it a candidate to
serve as a new kind of optical clock, that relies on many-body
entanglement between the emitters.
Our new experimental device will consist of an effusive beam of
strontium atoms, in high vacuum. This atomic beam will first be
slowed down by a laser beam; the atoms will then be excited into a
metastable electronic state, before entering between two mirrors,
within the mode of a high-finesse Fabry-Perot cavity. When the
density of the atoms passing through the cavity is high enough, a
cooperative effect known as super-radiance should occur, which
increases the spontaneous emission rate and ensures that it will
take place preferentially towards the fundamental mode of the
Fabry-Perot cavity. Some original characteristics of this light
source are an emission frequency mostly set by the atoms and thus
robust with respect to perturbations of the system, and a
linewidth that, thanks to the quantum correlations between
emitters, can be even below that of individual emitters.
The internship will be of a purely experimental nature. It will
consist on the one hand in setting up the lasers that will allow
to manipulate the strontium atoms, in order to create a
monokinetic jet, colimated, and directed towards the Fabry-Perot
cavity under vacuum. A first laser is an extended cavity laser
operating at 461 nm. The laser will first be characterized. An
acousto-optic optical setup will be used to create all the laser
beams allowing: the transverse cooling of the atoms' motion; the
longitudinal slowing down of the atoms; the deflection of the
atoms thus slowed down by a well controlled angle, so that they
propagate towards the Fabry-Perot cavity. A second laser will also
be set up. It is an extended cavity laser, which operates at 689
nm. Here again, a complex optical system will be set up. The
purpose of this system is to target the atoms using a highly
divergent beam, in order to achieve the necessary population
inversion to produce the desired laser effect.
Our team is composed of three professors, two CNRS researchers,
three PhD students and one post-doc. We currently have two running
experiments to study the collective properties of spinful
ultracold gases, marked by quantum physics. We welcome (almost)
every year one or more trainees on one of our experiments. Each
time, we proposed an individualized work subject to the trainee,
work that he/she could develop in autonomy while being put in
connection with the rest of the team and its scientific projects.
Martin Robert de Saint Vincent, Bruno Laburthe-Tolra