19 research outputs found
A comparsion of force sensors for atomic force microscopy based on quartz tuning forks and length extensional resonators
The force sensor is key to the performance of atomic force microscopy (AFM).
Nowadays, most AFMs use micro-machined force sensors made from silicon, but
piezoelectric quartz sensors are applied at an increasing rate, mainly in
vacuum. These self sensing force sensors allow a relatively easy upgrade of a
scanning tunneling microscope to a combined scanning tunneling/atomic force
microscope. Two fundamentally different types of quartz sensors have achieved
atomic resolution: the 'needle sensor' that is based on a length extensional
resonator and the 'qPlus sensor' that is based on a tuning fork. Here, we
calculate and measure the noise characteristics of these sensors. We find four
noise sources: deflection detector noise, thermal noise, oscillator noise and
thermal drift noise. We calculate the effect of these noise sources as a factor
of sensor stiffness, bandwidth and oscillation amplitude. We find that for self
sensing quartz sensors, the deflection detector noise is independent of sensor
stiffness, while the remaining three noise sources increase strongly with
sensor stiffness. Deflection detector noise increases with bandwidth to the
power of 1.5, while thermal noise and oscillator noise are proportional to the
square root of the bandwidth. Thermal drift noise, however, is inversely
proportional to bandwidth. The first three noise sources are inversely
proportional to amplitude while thermal drift noise is independent of the
amplitude. Thus, we show that the earlier finding that quoted optimal
signal-to-noise ratio for oscillation amplitudes similar to the range of the
forces is still correct when considering all four frequency noise
contributions. Finally, we suggest how the signal-to-noise ratio of the sensors
can be further improved and briefly discuss the challenges of mounting tips.Comment: 40 pages, 14 figure
Probing thermal magnon current mediated by coherent magnon via nitrogen-vacancy centers in diamond
Currently, thermally excited magnons are being intensively investigated owing
to their potential in computing devices and thermoelectric conversion
technologies. We report the detection of thermal magnon current propagating in
a magnetic insulator yttrium iron garnet under a temperature gradient using a
quantum sensor: electron spins associated with nitrogen-vacancy (NV) centers in
diamond. Thermal magnon current was observed as modified Rabi oscillation
frequencies of NV spins hosted in a beam-shaped bulk diamond that resonantly
coupled with coherent magnon propagating over a long distance. Additionally,
using a nanodiamond, alteration in NV-spin relaxation rates depending on the
applied temperature gradient were observed under a non-resonant NV excitation
condition. The demonstration of probing thermal magnon current mediated by
coherent magnon via NV-spin states serves as a basis for creating a new device
platform hybridizing spin caloritronics and spin qubits.Comment: 43 pages, 4 figure
Continuous Generation of Spinmotive Force in a Patterned Ferromagnetic Film
We study, both experimentally and theoretically, the generation of a dc
spinmotive force. By exciting a ferromagnetic resonance of a comb-shaped
ferromagnetic thin film, a continuous spinmotive force is generated.
Experimental results are well reproduced by theoretical calculations, offering
a quantitative and microscopic understanding of this spinmotive force.Comment: 4 pages, 4 figures, accepted to Physical Review Letter
Quantum-grade nanodiamonds for ultrabright spin detection in live cells
Optically accessible spin-active nanomaterials are promising as quantum
nanosensors for probing biological samples. However, achieving bioimaging-level
brightness and high-quality spin properties for these materials is challenging
and hinders their application in quantum biosensing. Here, we demonstrate
ultrabright fluorescent nanodiamonds (NDs) containing 0.6-1.3-ppm
nitrogen-vacancy (NV) centers by spin-environment engineering via enriching
spin-less 12C-carbon isotopes and reducing substitutional nitrogen spin
impurities. The NDs, readily introduced into cultured cells, exhibited
substantially narrow optically detected magnetic resonance (ODMR) spectra,
requiring 16-times less microwave excitation power to give an ODMR depth
comparable to that of conventional type-Ib NDs. They show average
spin-relaxation times of T1 = 0.68 ms and T_2 = 1.6 us (1.6 ms and 2.7 us
maximum) that were 5- and 11-fold longer than those of type-Ib, respectively.
The bulk-like NV spin properties and bright fluorescence demonstrated in this
study significantly improve the sensitivity of ND-based quantum sensors for
biological applications
Giant nonlinear optical effects induced by nitrogen-vacancy centers in diamond crystals
We investigate the effect of nitrogen-vacancy (NV) centers in single crystal diamond on nonlinear optical effects using 40 fs femtosecond laser pulses. The near-infrared femtosecond pulses allow us to study purely nonlinear optical effects, such as optical Kerr effect (OKE) and two-photon absorption (TPA), related to unique optical transitions by electronic structures with NV centers. It is found that both nonlinear optical effects are enhanced by the introduction of NV centers in the N+ dose levels of 2.0×1011 and 1.0×1012 N+/cm2. In particular, our data demonstrate that the OKE signal is strongly enhanced for the heavily implanted type-IIa diamond. We suggest that the strong enhancement of the OKE is possibly originated from cascading OKE, where the high-density NV centers effectively break the inversion symmetry near the surface region of diamond
Spin dynamics of a solid-state qubit in proximity to a superconductor
A broad effort is underway to understand and harness the interaction between
superconductors and spin-active color centers with an eye on the realization of
hybrid quantum devices and novel imaging modalities of superconducting
materials. Most work, however, overlooks the complex interplay between either
system and the environment created by the color center host. Here we use an
all-diamond scanning probe to investigate the spin dynamics of a single
nitrogen-vacancy (NV) center proximal to a high-critical-temperature
superconducting film in the presence of a weak magnetic field. We find that the
presence of the superconductor increases the NV spin coherence lifetime, a
phenomenon we tentatively rationalize as a change in the electric noise due to
a superconductor-induced redistribution of charge carriers near the NV site. We
build on these findings to demonstrate transverse-relaxation-time-weighted
imaging of the superconductor film. These results shed light on the complex
surface dynamics governing the spin coherence of shallow NVs while
simultaneously paving the route to new forms of noise spectroscopy and imaging
of superconductors