26 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
Chern-Simons theory on L(p,q) lens spaces and Gopakumar-Vafa duality
We consider aspects of Chern-Simons theory on L(p,q) lens spaces and its
relation with matrix models and topological string theory on Calabi-Yau
threefolds, searching for possible new large N dualities via geometric
transition for non-SU(2) cyclic quotients of the conifold. To this aim we find,
on one hand, some novel matrix integral representations of the SU(N) CS
partition function in a generic flat background for the whole L(p,q) family and
provide a solution for its large N dynamics; on the other, we perform in full
detail the construction of a family of would-be dual closed string backgrounds
via conifold geometric transition from T^*L(p,q). We can then explicitly prove
that Gopakumar-Vafa duality in a fixed vacuum fails in the case q>1, and
briefly discuss how it could be restored in a non-perturbative setting.Comment: 17 pages, 6 figures; references adde
Breaking the superfluid speed limit in a fermionic condensate
Coherent condensates appear as emergent phenomena in many systems. They share the characteristic feature of an energy gap separating the lowest excitations from the condensate ground state. This implies that a scattering object, moving through the system with high enough velocity for the excitation spectrum in the scatterer frame to become gapless, can create excitations at no energy cost, initiating the breakdown of the condensate—the well-known Landau velocity. Whereas, for the neutral fermionic superfluid 3He-B in the T = 0 limit, flow around an oscillating body displays a very clear critical velocity for the onset of dissipation, here we show that for uniform linear motion there is no discontinuity whatsoever in the dissipation as the Landau critical velocity is passed and exceeded. Given the importance of the Landau velocity for our understanding of superfluidity, this result is unexpected, with implications for dissipative effects of moving objects in all coherent condensate systems
p-Wave Superconductivity in UBe13
The specific heat in the superconducting state of UBe13 shows marked deviations from BCS theory and obeys a T3 rather than an exponential law at low temperatures. A good description is obtained by the assumption of an Anderson-Brinkman-Morel p-wave superconducting state at all temperatures. The value of the spin-fluctuation parameter deduced is large and consistent with the stability of such a state. © 1984 The American Physical Society