21 research outputs found
Spin Vortex in Magnon BEC of Superfluid 3He-B
The phenomenon of the spontaneous phase-coherent precession of magnetization
in superfluid 3He and the related effects of spin superfluidity are based on
the true Bose-Einstein condensation of magnons. Several different magnon BEC
states have been observed: homogeneously precessing domain (HPD); BEC
condensation in the spin-orbit potential trap (Q-balls); coherent precession
with fractional magnetization; and two modes of the coherent precession in
squeezed aerogel. The spin superfluidity effects, like spin Josephson
phenomena, spin current vortices, spin phase slippage, long distance
magnetization transport by spin supercurrents have been observed.Comment: 4 pages, 2 figures for proceedings of VORTEX V conferenc
NMR in Superfluid A-like Phase of He Confined in Globally Deformed Aerogel in Tilted Magnetic Field
NMR spectra in superfluid A-like phases confined in axially deformed aerogel
in presence of a magnetic field inclined with respect to deformation axis is
considered. The characteristic features of dipole frequency shift in axially
compressed and axially stretched cases are compared. In particular, it is shown
that in axially stretched aerogel environment the stability region of
coherently spin precessing mode is rather narrow due to the U(1)LIM effect.Comment: 8 pages, 2 figure
Low energy conversion electron detection in superfluid He3 at ultra-low temperature
We report on the first results of the MACHe3 (MAtrix of Cells of Helium 3)
prototype experiment concerning the measurement of low energy conversion
electrons at ultra-low temperature. For the first time, the feasibility of the
detection of low energy electrons is demonstrated in superfluid He3-B cooled
down to 100 microK. Low energy electrons at 7.3 keV coming from the K shell
conversion of the 14.4 keV nuclear transition of a low activity Co57 source are
detected, opening the possibility to use a He3-based detector for the detection
of Weakly Interacting Massive Particles (WIMPs) which are expected to release
an amount of energy higher-bounded by 5.6 keV.Comment: 8 pages, 3 figures, to appear in NIM
Vortex core contribution to textural energy in 3He-B below 0.4Tc
Vortex lines affect the spatial order-parameter distribution in superfluid
3He-B owing to superflow circulating around vortex cores and due to the
interaction of the order parameter in the core and in the bulk as a result of
superfluid coherence over the whole volume. The step-like change of the latter
contribution at 0.6Tc (at a pressure of 29bar) signifies the transition from
axisymmetric cores at higher temperatures to broken-symmetry cores at lower
temperatures. We extended earlier measurements of the core contribution to
temperatures below 0.2Tc, in particular searching for a possible new core
transition to lower symmetries. As a measuring tool we track the energy levels
of magnon condensate states in a trap formed by the order-parameter texture.Comment: 13 pages, 10 figures, submitted to proceedings of the QFS2010
conferenc
Electron - nuclear recoil discrimination by pulse shape analysis
In the framework of the ``ULTIMA'' project, we use ultra cold superfluid 3He
bolometers for the direct detection of single particle events, aimed for a
future use as a dark matter detector. One parameter of the pulse shape observed
after such an event is the thermalization time constant. Until now it was
believed that this parameter only depends on geometrical factors and superfluid
3He properties, and that it is independent of the nature of the incident
particles. In this report we show new results which demonstrate that a
difference for muon- and neutron events, as well as events simulated by heater
pulses exist. The possibility to use this difference for event discrimination
in a future dark matter detector will be discussed.Comment: Proseedings of QFS 2007, Kazan, Russia; 8 pages, 4 figures. Submited
to J. Low Temp. Phy
Search for Supersymmetric Dark Matter with Superfluid He3 (MACHe3)
MACHe3 (MAtrix of Cells of superfluid He3) is a project of a new detector for
direct Dark Matter search, using superfluid He3 as a sensitive medium. This
paper presents a phenomenological study done with the DarkSUSY code, in order
to investigate the discovery potential of this project of detector, as well as
its complementarity with existing and planned devices.Comment: 15 pages, 5 figures, submitted to Phys. Letters B, minor changes in
the tex
Magnon Condensation into a Q Ball in 3He−B
The theoretical prediction of Q balls in relativistic quantum fields is realized here experimentally in superfluid 3He−B. The condensed-matter analogs of relativistic Q balls are responsible for an extremely long-lived signal of magnetic induction observed in NMR at the lowest temperatures. This Q ball is another representative of a state with phase coherent precession of nuclear spins in 3He−B, similar to the well-known homogeneously precessing domain, which we interpret as Bose-Einstein condensation of spin waves—magnons. At large charge Q, the effect of self-localization is observed. In the language of relativistic quantum fields it is caused by interaction between the charged and neutral fields, where the neutral field provides the potential for the charged one. In the process of self-localization the charged field modifies locally the neutral field so that the potential well is formed in which the charge Q is condensed.Peer reviewe
Texture dependence of the persistent NMR signal in superfluid3He-B.
We have studied coherent magnetization precession in superfluid3He with pulsed NMR to temperatures of ≈0.1T c. Persistent signals were observed with lifetimes up to 60s at a frequency of 0.8MHz. We have found that the behaviour is reproducible for small levels of NMR excitation, whilst becoming irreproducible for higher excitations. We infer from this that textures play an essential role in the formation of persistent signals