A. N. Yudin

Polar Phase of Superfluid (3)He in Anisotropic Aerogel.

We report the first observation of the polar phase of superfluid (3)He. This phase appears in (3)He confined in a new type of aerogel with a nearly parallel arrangement of strands which play the role of ordered impurities. Our experiments qualitatively agree with theoretical predictions and suggest that in other systems with unconventional Cooper pairing (e.g., in unconventional superconductors) similar phenomena may be found in the presence of anisotropic impurities.

Orbital glass and spin glass states of 3He-A in aerogel

AbstractGlass states of superfluid A-like phase of 3He in aerogel induced by random orientations of aerogel strands are investigated theoretically and experimentally. In anisotropic aerogel with stretching deformation two glass phases are observed. Both phases represent the anisotropic glass of the orbital ferromagnetic vector Ηthe orbital glass (OG). The phases differ by the spin structure: the spin nematic vector

Observation of Half-Quantum Vortices in Topological Superfluid 3He

\hat d

B phase with polar distortion in superfluid 3He in “ordered” aerogel

can be either in the ordered spin nematic (SN) state or in the disordered spin-glass (SG) state. The first phase (OG-SN) is formed under conventional cooling from normal 3He. The second phase (OG-SG) is metastable, being obtained by cooling through the superfluid transition temperature, when large enough resonant continuous radio-frequency excitation is applied. NMR signature of different phases allows us to measure the parameter of the global anisotropy of the orbital glass induced by deformation.

Anisotropic 2D Larkin-Imry-Ma state in the polar distorted ABM phase of 3He in a “nematically ordered” aerogel

Results of experiments with liquid 3He immersed in a new type of aerogel are described. This aerogel consists of Al2O3 · H2O strands which are nearly parallel to each other, so we call it as a “nematically ordered” aerogel. At all used pressures a superfluid transition was observed and a superfluid phase diagram was measured. Possible structures of the observed superfluid phases are discussed.

Anisotropic spin diffusion in liquid 3He confined in nafen

One of the most sought-after objects in topological quantum-matter systems is a vortex carrying half a quantum of circulation. They were originally predicted to exist in superfluid ^{3}He-A but have never been resolved there. Here we report an observation of half-quantum vortices (HQVs) in the polar phase of superfluid ^{3}He. The vortices are created with rotation or by the Kibble-Zurek mechanism and identified based on their nuclear magnetic resonance signature. This discovery provides a pathway for studies of unpaired Majorana modes bound to the HQV cores in the polar-distorted A phase.

Interaction of two magnetic resonance modes in the polar phase of superfluid 3He

The microstructure, specific area, and mechanical properties of various samples of “nematically ordered” aerogels whose strands are almost parallel to each other at macroscopic distances have been studied. The strong anisotropy of such aerogels distinguishes them from standard aerogels, which are synthesized by solgel technology, and opens new possibilities for physical experiments.

Measurements of spin diffusion in liquid 3He in “ordered” aerogel

The properties of the low-temperature superfluid phase of 3He in “nematically ordered” aerogel in which strands are almost parallel to one another are investigated by nuclear magnetic resonance methods. Such a strong anisotropy of the aerogel affects the phase diagram of 3He and the structure of superfluid phases. A theoretical model of the B phase with polar distortion is developed. It is shown that this model successfully describes the observed properties of the low-temperature phase.