A central part of the story of the discovery of superfluid 3He is the cooling technique used for the experiments, the Pomeranchuk effect. Although it is not an especially useful technique for obtaining low temperatures today, it contains my favorite example of the use of the Clausius-Clapeyron equation. The cooling technique is fun to describe in undergraduate physics classes on thermodynamics....

The superfluid phases of 3He provide a unique physical system to study the dynamical effects of spontaneous symmetry breaking in condensed matter. The theory of superfluid 3He is grounded in what are arguably two of the most successful theories of strongly interacting matter, Landau’s Fermi-liquid theory and the BCS pairing theory of superconductivity. These two theories were placed into a comm...

The physics of graphene and of the superfluid phases of 3He have many common features. Both systems are topological materials where quasiparticles behave as relativistic massless (Weyl, Majorana or Dirac) fermions. We formulate the points where these features are overlapping. This will allow us to use graphene to study the properties of superfluid 3He, to use superfluid 3He to study the propert...

We treat in detail positron production from the decay of radioactive nuclei produced in nuclear reactions of accelerated 3He. Because of their large cross sections and low threshold energies, these reactions can significantly contribute to positron production in solar flares with accelerated-particle compositions enriched in 3He. The addition of these 3He reactions extends earlier calculations ...

The ratio 3He/4He (R) plays a central role in models of mantle evolution that propose an undegassed lower mantle, rich in the primordial isotope 3He. A large primordial volatile-rich reservoir, a feature of recent models, is inconsistent with high-temperature accretion and with estimates of crustal and bulk Earth chemistry. High R can alternatively reflect high integrated 3He/(U+Th) ratios or l...

We have examined the superfluidity of 3He in 98.2% porous silica aerogel with up to 34% 4He at 21.6 bars. The mixture is phase separated for 4He fractions between ,11% and 34%, and the 4Herich phase preferentially occupies the regions of highest silica density in the aerogel, thus modifying the distribution of the correlated disorder seen by superfluid 3He. The 3He Tc increases slightly with 4H...

A Hubbard-like Hamiltonian is used to study exchange-effects in solid 3He when a few 4He atoms are present as impurities. A canonical transformation has been performed to arrive at a Hamiltonian with terms that describe exchange between two 3He atoms, and a 3He atom and a 4He atom. In an attempt to see to what extent the magnetic properties of pure solid 3He remain unaltered, an analog of the L...

Anodic bonding was used to fabricate a 10 mm diameter × 640 nm tall annular geometry suitable for torsion pendulum studies of confined 3He. For pure 3He at saturated vapor pressure the inertia of the confined fluid was seen to be only partially coupled to the pendulum at 160 mK. Below 100 mK the liquid’s inertial contribution was negligible, indicating a complete decoupling of the 3He from the ...

When immersed in liquid 3He, the nanometer strands of aerogel are coated with a thin layer of solid 3He, forming a network of irregular nanotubes. Owing to its high purity and weak interactions, this system is ideal for studying fundamental processes. We report the first experiments on solid 3He in aerogel at ultralow temperatures, cooled by direct adiabatic demagnetization. Simultaneous nuclea...

We report the first observation of longitudinal sound propagation in three dimensionally distributed Bose and Fermi superfluids in an acoustic investigation of phase separated 3He-4He mixtures confined to aerogel. At mK temperatures, this inhomogeneous system exhibits simultaneous 3He and 4He superfluidity leading to two "slow modes" along with the conventional sound mode. We also infer the sup...