Direct observation of Majorana in 3He. – MajoranaPRO

Investigations at the lowest temperature are one of the frontiers of science. Today, our laboratory at the Institut Néel and the Low Temperature laboratory at Lancaster University keep the world record of matter cooling, which is 0.085 mK. This very low temperature limit is important for the physics of 3He, which undergoes a phase transition to the superfluid state at about 1 mK. At ultralow temperatures, superfluid 3He exhibits the properties of a quantum vacuum, with a very low density of thermal excitations.

Since we are only single group, working in France at so low temperatures, it is essential for us to have an international collaboration. We are involved in the European project “MicroKelvin” where we are collaborates with Lancaster University group and the Helsinki Aalto University group. This collaboration considers our group as one of international facility for the investigations at the frontier of Low Temperature Physics. Indeed, it does not supply money for support of our current investigations and for upgrade the facility and it will be finished in September 2013. After this date we will continue our collaboration on a non-formal ground.

In the current project we are planning to make an ambiguous search of majorana fermions in superfluid 3He by its heat capacity. The superfluid 3He B phase are receiving renewed attention as ‘‘edge states’’ of a three-dimensional (3D) time reversal invariant topological superfluid. Topological superfluids and superconductors are characterized by a non-trivial topological number in the gapped bulk state and a gapless edge state on their edges or surfaces. SABS of the superfluid 3He B phase can be regarded as Majorana fermions as they satisfy the Majorana condition, i.e., a particle and its antiparticle are equivalent, because the degrees of freedom of the bound states are halved. Apparently, we have developed a very sensitive bolometer for Dark Matter searching on a basis of superfluid 3He at the temperature 100 microK. As we will show in scientific part of the proposal, we are able to get conditions, when the heat capacity of bulk 3He will be so small, so we are able to measure directly the heat capacity of majorano fermions. In our previous experiments we have observed the increasing of heat capacity due to Majorana. In experiments, we propose, we will be able to get the conditions, when the heat capacity of Majorana will be 10 times bigger than the bulk quasiparticles. Be made, this experiment will be the first direct proof of the existence of majorano fermions since the other types of edge particles has a very different temperature dependence of heat capacity.

The second method of majorana observation is the NMR of so named Q-ball, a self-localized state of coherent spin waves. This original method was developed by our group. The density of majorana states can be measured by relaxation rate of Q-ball. The similar experiment with the electron ball in superfluid 3He is under progress in RIKEN Institute, Japan. We are in good non-formal collaboration with this group.