15 research outputs found
New Chiral Phases of Superfluid 3He Stabilized by Anisotropic Silica Aerogel
A rich variety of Fermi systems condense by forming bound pairs, including
high temperature [1] and heavy fermion [2] superconductors, Sr2RuO4 [3], cold
atomic gases [4], and superfluid 3He [5]. Some of these form exotic quantum
states having non-zero orbital angular momentum. We have discovered, in the
case of 3He, that anisotropic disorder, engineered from highly porous silica
aerogel, stabilizes a chiral superfluid state that otherwise would not exist.
Additionally, we find that the chiral axis of this state can be uniquely
oriented with the application of a magnetic field perpendicular to the aerogel
anisotropy axis. At suffciently low temperature we observe a sharp transition
from a uniformly oriented chiral state to a disordered structure consistent
with locally ordered domains, contrary to expectations for a superfluid glass
phase [6].Comment: 6 pages, 4 figure, and Supplementary Informatio
Bose-Einstein Condensation in Magnetic Insulators
The elementary excitations in antiferromagnets are magnons, quasiparticles
with integer spin and Bose statistics. In an experiment their density is
controlled efficiently by an applied magnetic field and can be made finite to
cause the formation of a Bose-Einstein condensate (BEC). Studies of magnon
condensation in a growing number of magnetic materials provide a unique window
into an exciting world of quantum phase transitions (QPT) and exotic quantum
states.Comment: 17 pages, 3 figure
Superfluid He-3 simulation of cosmic string creation in the early universe
We discuss the first experimental observations of a deficit in the thermal energy released after the exothermic neutron-He-3 nuclear reaction in superfluid He-3 at temperatures approaching 100 mu K. We propose that this deficit is associated with the creation of a vortex tangle as the liquid He-3 recrosses the superfluid transition. This process has many similarities with the theory of cosmic string creation during the GUT and electro weak transitions shortly after the Big Bang. Our measurements constitute the first quantitative test of defect creation via the cosmological Kibble mechanism for gauge symmetry breaking phase transitions and agree very well with the predictions of Zurek's scenario
Potential dark matter detector?:the detection of low energy neutrons by superfluid 3He
Using an existing experiment we have demonstrated in a pilot study that superfluid He-3 at 100 mu K can be used as a nuclear recoil detector sensitive to neutron and gamma interactions depositing energies down to a few hundred eV. The deposited energy is converted to He-3 quasiparticles which are detected by their damping effect on a vibrating wire resonator in the liquid. The system can be calibrated independently but a convenient fixed point is provided by the exothermic reaction n + He-3(2) = p + H-3(1) + 764 keV. Given the great potential for improvement we propose that the system might make a sensitive weakly interacting massive particle detector