6,182 research outputs found
Superfluid Optomechanics: Coupling of a Superfluid to a Superconducting Condensate
We investigate the low loss acoustic motion of superfluid He
parametrically coupled to a very low loss, superconducting Nb, TE
microwave resonator, forming a gram-scale, sideband resolved, optomechanical
system. We demonstrate the detection of a series of acoustic modes with quality
factors as high as . At higher temperatures, the lowest
dissipation modes are limited by an intrinsic three phonon process. Acoustic
quality factors approaching may be possible in isotopically purified
samples at temperatures below 10 mK. A system of this type may be utilized to
study macroscopic quantized motion and as an ultra-sensitive sensor of
extremely weak displacements and forces, such as continuous gravity wave
sources
Ultra-high Q Acoustic Resonance in Superfluid 4He
We report the measurement of the acoustic quality factor of a gram-scale,
kilo-hertz frequency superfluid resonator, detected through the parametric
coupling to a superconducting niobium microwave cavity. For temperature between
400mK and 50mK, we observe a temperature dependence of the quality
factor, consistent with a 3-phonon dissipation mechanism. We observe Q factors
up to , consistent with the dissipation due to dilute He
impurities, and expect that significant further improvements are possible.
These experiments are relevant to exploring quantum behavior and decoherence of
massive macroscopic objects, the laboratory detection of continuous wave
gravitational waves from pulsars, and the probing of possible limits to
physical length scales.Comment: 5 pages, 2 figure
Results from new fungus-tolerant grapevine varieties for Organic Viticulture
Two red and three white new fungus-tolerant grape varieties were tested within a period of five years. REGENT, RONDO, JOHANNITER and Gf 48-12 show a better wine quality than PINOT NOIR or SILVANER and can be recommended for Organic Viticulture as well as for the conventional viticulture to reduce copper and fungicide applications
Anisotropic conductivity of disordered 2DEGs due to spin-orbit interactions
We show that the conductivity tensor of a disordered two-dimensional electron
gas becomes anisotropic in the presence of both Rashba and Dresselhaus
spin-orbit interactions (SOI). This anisotropy is a mesoscopic effect and
vanishes with vanishing charge dephasing time. Using a diagrammatic approach
including zero, one, and two-loop diagrams, we show that a consistent
calculation needs to go beyond a Boltzmann equation approach. In the absence of
charge dephasing and for zero frequency, a finite anisotropy \sigma_{xy}
e^2/lhpf arises even for infinitesimal SOI.Comment: 6+ page
Sum rules for spin-Hall conductivity cancelation
It has been shown recently that the universal dc spin conductivity of
two-dimensional electrons with a Rashba spin-orbit interaction is canceled by
vertex corrections in a weak scattering regime. We prove that the zero bulk
spin conductivity is an intrinsic property of the free-electron Hamiltonian and
scattering is merely a tool to reveal this property in terms of the
diagrammatic technique. When Zeeman energy is neglected, the zero dc
conductivity persists in a magnetic field. Spin conductivity increases
resonantly at the cyclotron frequency and then decays towards the universal
value.Comment: 4 pages, 1 figur
Bat Activity Patterns and Roost Selection in Managed Forests
The recent introduction and subsequent westward spread of white-nose syndrome (WNS) has decimated hibernating bat populations in eastern North America and created an urgent need for scientists to understand basic information about bat ecology, especially during the winter season. White-nose syndrome has killed between 5 and 7 million bats and continues to spread westward from the eastern U.S. and southern Canada, primarily affecting bats during hibernation. Acoustic monitoring has been suggested as a potential surveillance tool for detecting WNS; however, baseline information must first be collected to test this technique. We initiated a pilot project in June 2014 by deploying 2 remote acoustic monitoring stations in western Montana’s managed forests collecting baseline acoustic information. We also conducted radio telemetry to determine characteristics of roosts used by bats during the fall season. Thus far we have recorded 11 of Montana’s 15 bat species, and observed extremely high activity levels during the summer. We radio-tagged 5 bats of 3 different species (California myotis, Western small-footed myotis, Silver-haired bat) and tracked them in late October and early November. Identifying the characteristics of roost sites used during the pre-hibernation period, and the annual activity patterns determined from acoustic monitoring, begin to form the foundation for understanding basic aspects of bat ecology during the season when Montana bats will be most susceptible to WNS
Bat Activity Patterns and Roost Selection in Managed Forests
The recent introduction and subsequent westward spread of white-nose syndrome (WNS) has decimated hibernating bat populations in eastern North America and created an urgent need for scientists to understand basic information about bat ecology, especially during the winter season. White-nose syndrome has killed between 5 and 7 million bats and continues to spread westward from the eastern U.S. and southern Canada, primarily affecting bats during hibernation. Acoustic monitoring has been suggested as a potential surveillance tool for detecting WNS; however, baseline information must first be collected to test this technique. Recent interests in habitat for resident bats has focused on managed forests, particularly in western Montana, where caves used as communal winter hibernacula are not abundant. We initiated a pilot project in June 2014 deploying 2 remote acoustic monitoring stations on Plum Creek property in Flathead County and adding an additional 2 stations in forests owned by Stoltze Land and Lumber and Stimson Lumber Company in May 2015 to collect baseline acoustic information. We also conducted radio telemetry to determine characteristics of roosts used by bats during the fall season in 2014 and 2015. Thus far we have acoustically detected 11 of Montana’s 15 bat species, observed extremely high activity levels during the summer, and detected bat activity during every month of the year. We radio-tagged 14 bats of 4 different species; California myotis (Myotis californicus), Western small-footed myotis (Myotis ciliolabrum), Silver-haired bat (Lasionycteris noctivagans), Little brown bat (Myotis lucifugus) and tracked them in late October and early November. Identifying the characteristics of roost sites used during the pre-hibernation period, and the annual activity patterns determined from acoustic monitoring, begin to form the foundation for understanding basic aspects of bat ecology during the season when Montana bats will be most susceptible to WNS
Stochastic heating of a molecular nanomagnet
We study the excitation dynamics of a single molecular nanomagnet by static
and pulsed magnetic fields. Based on a stability analysis of the classical
magnetization dynamics we identify analytically the fields parameters for which
the energy is stochastically pumped into the system in which case the
magnetization undergoes diffusively and irreversibly a large angle deflection.
An approximate analytical expression for the diffusion constant in terms of the
fields parameters is given and assessed by full numerical calculations.Comment: 5 pages, 4 figures, to appear in Phys. Rev.
Momentum-resolved evolution of the Kondo lattice into 'hidden-order' in URu2Si2
We study, using high-resolution angle-resolved photoemission spectroscopy,
the evolution of the electronic structure in URu2Si2 at the Gamma, Z and X
high-symmetry points from the high-temperature Kondo-screened regime to the
low-temperature `hidden-order' (HO) state. At all temperatures and symmetry
points, we find structures resulting from the interaction between heavy and
light bands, related to the Kondo lattice formation. At the X point, we
directly measure a hybridization gap of 11 meV already open at temperatures
above the ordered phase. Strikingly, we find that while the HO induces
pronounced changes at Gamma and Z, the hybridization gap at X does not change,
indicating that the hidden-order parameter is anisotropic. Furthermore, at the
Gamma and Z points, we observe the opening of a gap in momentum in the HO
state, and show that the associated electronic structure results from the
hybridization of a light electron band with the Kondo-lattice bands
characterizing the paramagnetic state.Comment: Updated published version. Mansucript + Supplemental Material (8
pages, 9 figures). Submitted 16 September 201
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