29 research outputs found
Resolving High Amplitude Surface Motion with Diffusing Light
A new technique has been developed for the purpose of imaging high amplitude surface motion. With this method one can quantitatively measure the transition to ripple wave turbulence. In addition, one can measure the phase of the turbulent state. These experiments reveal strong coherent structures in turbulent range of motion
Pressure- and Field-Tuning the Magnetostructural Phases of Mn3O4: Raman Scattering and X-Ray Diffraction Studies
We present temperature-, magnetic-field-, and pressure-dependent Raman
scattering studies of single crystal Mn3O4, combined with temperature- and
field-dependent x-ray diffraction studies, revealing the novel
magnetostructural phases in Mn3O4. Our temperature-dependent studies showed
that the commensurate magnetic transition at T2=33K in the binary spinel Mn3O4
is associated with a structural transition from tetragonal to orthorhombic
structures. Field-dependent studies showed that the onset and nature of this
structural transition can be controlled with an applied magnetic field, and
revealed evidence for a field-tuned quantum phase transition to a tetragonal
spin-disordered phase for H||[1-10]. Pressure-dependent Raman measurements
showed that the magnetic easy axis direction in Mn3O4 can be controlled---and
the ferrimagnetic transition temperature increased---with applied pressure.
Finally, combined pressure- and magnetic-field-tuned Raman measurements
revealed a rich magnetostructural phase diagram---including a pressure- and
field-induced magnetically frustrated tetragonal phase in the PH phase
diagram---that can be generated in Mn3O4 with applied pressure and magnetic
field.Comment: 12 pages, 13 figures, to be published in Phys. Rev.
Nanomechanical detection of nuclear magnetic resonance using a silicon nanowire oscillator
We report the use of a silicon nanowire mechanical oscillator as a
low-temperature nuclear magnetic resonance force sensor to detect the
statistical polarization of 1H spins in polystyrene. Under operating
conditions, the nanowire experienced negligible surface-induced dissipation and
exhibited a nearly thermally-limited force noise of 1.9 aN^2/Hz in the
measurement quadrature. In order to couple the 1H spins to the nanowire
oscillator, we have developed a new magnetic resonance force detection protocol
which utilizes a nanoscale current-carrying wire to produce large
time-dependent magnetic field gradients as well as the rf magnetic field.Comment: 14 pages, 5 figure
Dynamical Axion Field in Topological Magnetic Insulators
Axions are very light, very weakly interacting particles postulated more than
30 years ago in the context of the Standard Model of particle physics. Their
existence could explain the missing dark matter of the universe. However,
despite intensive searches, they have yet to be detected. In this work, we show
that magnetic fluctuations of topological insulators couple to the
electromagnetic fields exactly like the axions, and propose several experiments
to detect this dynamical axion field. In particular, we show that the axion
coupling enables a nonlinear modulation of the electromagnetic field, leading
to attenuated total reflection. We propose a novel optical modulators device
based on this principle.Comment: 5 pages, 3 figure
Harnessing nuclear spin polarization fluctuations in a semiconductor nanowire
Soon after the first measurements of nuclear magnetic resonance (NMR) in a
condensed matter system, Bloch predicted the presence of statistical
fluctuations proportional to in the polarization of an ensemble of
spins. First observed by Sleator et al., so-called "spin noise" has
recently emerged as a critical ingredient in nanometer-scale magnetic resonance
imaging (nanoMRI). This prominence is a direct result of MRI resolution
improving to better than 100 nm^3, a size-scale in which statistical spin
fluctuations begin to dominate the polarization dynamics. We demonstrate a
technique that creates spin order in nanometer-scale ensembles of nuclear spins
by harnessing these fluctuations to produce polarizations both larger and
narrower than the natural thermal distribution. We focus on ensembles
containing ~10^6 phosphorus and hydrogen spins associated with single InP and
GaP nanowires (NWs) and their hydrogen-containing adsorbate layers. We monitor,
control, and capture fluctuations in the ensemble's spin polarization in
real-time and store them for extended periods. This selective capture of large
polarization fluctuations may provide a route for enhancing the weak magnetic
signals produced by nanometer-scale volumes of nuclear spins. The scheme may
also prove useful for initializing the nuclear hyperfine field of electron spin
qubits in the solid-state.Comment: 18 pages, 5 figure
Hybrid Mechanical Systems
We discuss hybrid systems in which a mechanical oscillator is coupled to
another (microscopic) quantum system, such as trapped atoms or ions,
solid-state spin qubits, or superconducting devices. We summarize and compare
different coupling schemes and describe first experimental implementations.
Hybrid mechanical systems enable new approaches to quantum control of
mechanical objects, precision sensing, and quantum information processing.Comment: To cite this review, please refer to the published book chapter (see
Journal-ref and DOI). This v2 corresponds to the published versio
Magnetic Resonance Force Microscopy of paramagnetic electron spins at millikelvin temperatures
Magnetic Resonance Force Microscopy (MRFM) is a powerful technique to detect
a small number of spins that relies on force-detection by an ultrasoft
magnetically tipped cantilever and selective magnetic resonance manipulation of
the spins. MRFM would greatly benefit from ultralow temperature operation,
because of lower thermomechanical noise and increased thermal spin
polarization. Here, we demonstrate MRFM operation at temperatures as low as 30
mK, thanks to a recently developed SQUID-based cantilever detection technique
which avoids cantilever overheating. In our experiment, we detect dangling bond
paramagnetic centers on a silicon surface down to millikelvin temperatures.
Fluctuations of such kind of defects are supposedly linked to 1/f magnetic
noise and decoherence in SQUIDs as well as in several superconducting and
single spin qubits. We find evidence that spin diffusion plays a key role in
the low temperature spin dynamics.Comment: 7 pages, 5 figure