17 research outputs found
Spatiotemporal Mapping of Photocurrent in a Monolayer Semiconductor Using a Diamond Quantum Sensor
The detection of photocurrents is central to understanding and harnessing the
interaction of light with matter. Although widely used, transport-based
detection averages over spatial distributions and can suffer from low
photocarrier collection efficiency. Here, we introduce a contact-free method to
spatially resolve local photocurrent densities using a proximal quantum
magnetometer. We interface monolayer MoS2 with a near-surface ensemble of
nitrogen-vacancy centers in diamond and map the generated photothermal current
distribution through its magnetic field profile. By synchronizing the
photoexcitation with dynamical decoupling of the sensor spin, we extend the
sensor's quantum coherence and achieve sensitivities to alternating current
densities as small as 20 nA per micron. Our spatiotemporal measurements reveal
that the photocurrent circulates as vortices, manifesting the Nernst effect,
and rises with a timescale indicative of the system's thermal properties. Our
method establishes an unprecedented probe for optoelectronic phenomena, ideally
suited to the emerging class of two-dimensional materials, and stimulates
applications towards large-area photodetectors and stick-on sources of magnetic
fields for quantum control.Comment: 19 pages, 4 figure
Heritability of non-speech auditory processing skills
Recent insight into the genetic bases for autism spectrum disorder, dyslexia, stuttering, and language disorders suggest that neurogenetic approaches may also reveal at least one etiology of auditory processing disorder (APD). A person with an APD typically has difficulty understanding speech in background noise despite having normal pure-tone hearing sensitivity. The estimated prevalence of APD may be as high as 10% in the pediatric population, yet the causes are unknown and have not been explored by molecular or genetic approaches. The aim of our study was to determine the heritability of frequency and temporal resolution for auditory signals and speech recognition in noise in 96 identical or fraternal twin pairs, aged 6–11 years. Measures of auditory processing (AP) of non-speech sounds included backward masking (temporal resolution), notched noise masking (spectral resolution), pure-tone frequency discrimination (temporal fine structure sensitivity), and nonsense syllable recognition in noise. We provide evidence of significant heritability, ranging from 0.32 to 0.74, for individual measures of these non-speech-based AP skills that are crucial for understanding spoken language. Identification of specific heritable AP traits such as these serve as a basis to pursue the genetic underpinnings of APD by identifying genetic variants associated with common AP disorders in children and adults
Recommended from our members
Spatiotemporal Mapping of a Photocurrent Vortex in Monolayer MoS<sub>2</sub> Using Diamond Quantum Sensors
Photocurrents are central to understanding and harnessing the interaction of light with matter. Here, we introduce a contact-free method to spatially resolve photocurrent distributions using proximal quantum magnetometers. We interface monolayer MoS2 with a near-surface ensemble of nitrogen-vacancy centers in diamond and map the generated photothermal current distribution through its magnetic-field profile. By synchronizing pulsed photoexcitation with dynamical decoupling of the sensor spin, we extend the sensor’s quantum coherence and resolve time-dependent, two-dimensional current densities as small as 20 nA / μm , with a projected sensitivity of 200 nA / (μm ) . Our spatially resolved measurements reveal that optical excitation can generate micron-sized photocurrent vortices in MoS2 , manifesting a photo-Nernst effect exceeding that of gate-tuned graphene at comparable magnetic fields. We further probe the rise time of the photocurrents and show that thermal diffusion determines its spatial variation. These spatiotemporal capabilities establish an optically accessed, local probe for optoelectronic phenomena, ideally suited to the emerging class of two-dimensional materials, for which making contacts is challenging and can alter the intrinsic material properties
Recommended from our members
Detecting Spin-Bath Polarization with Quantum Quench Phase Shifts of Single Spins in Diamond
Single-qubit sensing protocols can be used to measure qubit-bath coupling parameters. However, for sufficiently large coupling, the sensing protocol itself perturbs the bath, which is predicted to result in a characteristic response in the sensing measurements. Here, we observe this bath perturbation, also known as a quantum quench, by preparing the nuclear spin bath of a nitrogen-vacancy (NV) center in polarized initial states and performing phase-resolved spin-echo measurements on the NV electron spin. These measurements reveal a time-dependent phase determined by the initial state of the bath. We derive the relationship between the sensor phase and the Gaussian spin-bath polarization and apply it to reconstruct both the axial and transverse polarization components. Using this insight, we optimize the transfer efficiency of our dynamic nuclear polarization sequence. This technique for directly measuring bath polarization may assist in preparing high-fidelity quantum memory states, improving nanoscale NMR methods, and investigating non-Gaussian quantum baths
Assessment of auditory processing in 6-year-old language-impaired children.
Contains fulltext :
63068.pdf (publisher's version ) (Closed access)The performance of a group of twenty 6-year-old children with specific language impairment (SLI) on several behavioural auditory tests was compared to that of a group of twenty age-matched control children. The auditory test battery used in this study consisted of the following tests: a speech-in-noise test, a filtered speech test, a binaural fusion test, a frequency pattern test, a duration pattern test, a temporal integration test, an auditory word discrimination test, an auditory synthesis test, an auditory closure test and a number recall test. Our results show that the SLI children obtained scores on almost all tests that were significantly lower than those of the control group. Many of the basic auditory processing measures in our test battery correlated significantly with receptive and language scores, suggesting a (causal) relationship between auditory processing and language proficiency. Results from discriminant function analyses do not warrant deleting one or more tests from the test battery yet (with the exception of the auditory synthesis test and the temporal integration test, for which we did not find significant group effects). At present, we are conducting experiments with older (SLI and control) children and adults to find whether the significant performance deficits of the SLI children are also found in older SLI children, and to determine the influence of maturational effects on these auditory tests