Physics Research

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Data and scripts from: Room temperature optically detected magnetic resonance of single spins in GaN
Luo, Jialun; Geng, Yifei; Farhan, Rana; Fuchs, Gregory, D. (2024)
These files contain data and analysis code supporting all results reported in "Room temperature optically detected magnetic resonance of single spins in GaN" by Luo et al. In Luo et al. we found: High contrast optically detected magnetic resonance (ODMR) is a valuable property for reading out the spin of isolated defect color centers at room temperature. Spin-active single defect centers have been studied in wide bandgap materials including diamond, SiC, and hBN; each with associated advantages for applications. We report the discovery of ODMR in two distinct species of bright, isolated defect centers hosted in GaN. In one group, we find negative ODMR of a few percent associated with a metastable electronic state, whereas in the other, we find positive ODMR of up to 30% associated with the ground and optically excited electronic states. We examine the spin symmetry axis of each defect species and we establish coherent control over a single defect’s ground-state spin. Given the maturity of the semiconductor host, these results are promising for scalable and integrated quantum sensing applications
Data from: Observation of suppressed viscosity in the normal state of 3He due to superfluid fluctuations
Baten, Rakin, N.; Tian, Yefan; Smith, Eric N.; Mueller, Erich; Parpia, Jeevak M. (2023-10-05)
These files contain data supporting all results reported in Baten et. al. "Observation of suppressed viscosity in the normal state of 3He due to superfluid fluctuations". In Baten et al., we found that by monitoring the quality factor of a quartz tuning fork oscillator we observed a fluctuation-driven reduction in the viscosity of bulk 3He in the normal state near the superfluid transition temperature, Tc. These fluctuations, which are only found within $100 microK of Tc, play a vital role in the theoretical modeling of ordering; they encode details about the Fermi liquid parameters, pairing symmetry, and scattering phase shifts. They will be of crucial importance for transport probes of the topologically nontrivial features of superfluid 3He under strong confinement. Here we characterize the temperature and pressure dependence of the fluctuation signature, finding data collapse consistent with the predicted theoretical behavior.
Data from: Supercooling of the A phase of 3He
Tian, Yefan; Lotnyk, Dmytro; Eyal, Anna; Zhang, Kuang; Zhelev, Nikolay; Abhilash, T.S.; Chavez, Aldo; Smith, Eric N.; Hindermarsh, Mark; Saunders, John; Mueller, Erich; Parpia, Jeevak M. (2022-12-08)
These files contain data along with associated output from instrumentation supporting all results reported in Tien, et al, 2022, Supercooling of the A phase of 3He. In Tien, et al, 2022 we found: Because of the extreme purity, lack of disorder, and complex order parameter, the first-order superfluid 3He A-B transition is the leading model system for first order transitions in the early universe. Here we report on the path dependence of the supercooling of the A phase over a wide range of pressures below 29.3 bar at nearly zero magnetic field. The A phase can be cooled significantly below the thermodynamic A-B transition temperature. While the extent of supercooling is highly reproducible, it depends strongly upon the cooling trajectory: The metastability of the A phase is enhanced by transiting through regions where the A phase is more stable. We provide evidence that some of the additional supercooling is due to the elimination of B phase nucleation precursors formed upon passage through the superfluid transition. A greater understanding of the physics is essential before 3He can be exploited to model transitions in the early universe.
Data from: STRAINS: A Big Data Method for Classifying Cellular Response to Stimuli at the Tissue Scale
Zheng, Jingyang; Jackson, Thomas Wyse; Fortier, Lisa; Bonassar, Lawrence; Delco, Michelle; Cohen, Itai (2022)
These files contain data supporting all results reported in Zheng et. al., STRAINS: A Big Data Method for Classifying Cellular Response to Stimuli at the Tissue Scale. Cellular response to stimulation governs tissue scale processes ranging from growth and development to maintaining tissue health and initiating disease. To determine how cells coordinate their response to such stimuli, it is necessary to simultaneously track and measure the spatiotemporal distribution of their behaviors throughout the tissue. Here, we report on a novel SpatioTemporal Response Analysis IN Situ (STRAINS) tool that uses fluorescent micrographs, cell tracking, and machine learning to measure such behavioral distributions. STRAINS is broadly applicable to any tissue where fluorescence can be used to indicate changes in cell behavior. For illustration, we use STRAINS to simultaneously analyze the mechanotransduction response of 5000 chondrocytes---over 20 million data points---in cartilage during the 50 ms to 4 hours after the tissue was subjected to local mechanical injury, known to initiate osteoarthritis. We find that chondrocytes exhibit a range of mechanobiological responses indicating activation of distinct biochemical pathways with clear spatial patterns related to the induced local strains during impact. These results illustrate the power of this approach.
Code from: STRAINS: A Big Data Method for Classifying Cellular Response to Stimuli at the Tissue Scale
Zheng, Jingyang; Wyse Jackson, Thomas; Fortier, Lisa; Bonassar, Lawrence; Delco, Michelle; Cohen, Itai (2022-08-06)
These files contain data supporting all results reported in Zheng et. al., STRAINS: A Big Data Method for Classifying Cellular Response to Stimuli at the Tissue Scale. Cellular response to stimulation governs tissue scale processes ranging from growth and development to maintaining tissue health and initiating disease. To determine how cells coordinate their response to such stimuli, it is necessary to simultaneously track and measure the spatiotemporal distribution of their behaviors throughout the tissue. Here, we report on a novel SpatioTemporal Response Analysis IN Situ (STRAINS) tool that uses fluorescent micrographs, cell tracking, and machine learning to measure such behavioral distributions. STRAINS is broadly applicable to any tissue where fluorescence can be used to indicate changes in cell behavior. For illustration, we use STRAINS to simultaneously analyze the mechanotransduction response of 5000 chondrocytes---over 20 million data points---in cartilage during the 50 ms to 4 hours after the tissue was subjected to local mechanical injury, known to initiate osteoarthritis. We find that chondrocytes exhibit a range of mechanobiological responses indicating activation of distinct biochemical pathways with clear spatial patterns related to the induced local strains during impact. These results illustrate the power of this approach.
Data for: Neuromuscular embodiment of feedback control elements in Drosophila flight
Whitehead, Samuel C.; Leone, Sofia; Lindsay, Theodore; Meiselman, Matthew R.; Cowan, Noah; Dickinson, Michael; Yapici, Nilay; Stern, David L.; Shirangi, Troy; Cohen, Itai (2022)
These files contain data and code supporting all results reported in "Neuromuscular embodiment of feedback control elements in Drosophila flight" by Whitehead, et al. The abstract for that article is as follows: While insects like Drosophila are flying, aerodynamic instabilities require that they make millisecond-timescale adjustments to their wing motion to stay aloft and on course. These stabilization reflexes can be modeled as a proportional-integral (PI) controller; however, it is unclear how such control might be instantiated in insects at the level of muscles and neurons. Here, we show that the b1 and b2 motor units—prominent components of the fly’s steering muscles system—modulate specific elements of the PI controller: the angular displacement (integral, I) and angular velocity (proportional, P), respectively. Moreover, these effects are observed only during the stabilization of pitch. Our results provide evidence for an organizational principle in which each muscle contributes to a specific functional role in flight control, a finding that highlights the power of using top-down behavioral modeling to guide bottom-up cellular manipulation studies.
Data from: Structural Origins of Cartilage Shear Mechanics
Wyse Jackson, Thomas; Michel, Jonathan; Lwin, Pancy; Fortier, Lisa A.; Das, Moumita; Bonassar, Lawrence J.; Cohen, Itai (2022-02-22)
These files contain data supporting all results reported in Wyse Jackson et. al. . In Wyse Jackson et al., we found: Articular cartilage is a remarkable material able to sustain millions of loading cycles over decades of use outperforming any synthetic substitute. Crucially, how extracellular matrix constituents alter mechanical performance, particularly in shear, remains poorly understood. Here, we present experiments and theory in support of a rigidity percolation framework that quantitatively describes the structural origins of cartilage’s shear properties and how they arise from the mechanical interdependence of the collagen and aggrecan networks making up its extracellular matrix. This framework explains that near the cartilage surface, where the collagen network is sparse and close to the rigidity threshold, slight changes in either collagen or aggrecan concentrations, common in early stages of cartilage disease, create a marked weakening in modulus that can lead to tissue collapse. More broadly, this framework provides a map for understanding how changes in composition throughout the tissue alter its shear properties and ultimate in vivo function.
Nanoscale Magnetization and Current Imaging Using Time-Resolved Scanning-Probe Magnetothermal Microscopy
Zhang, Chi; Bartell, Jason M.; Karsch, Jonathan C.; Gray, Isaiah; Fuchs, Gregory D. (Nano Letters, 2021-06-08)
Magnetic microscopy that combines nanoscale spatial resolution with picosecond scale temporal resolution uniquely enables direct observation of the spatiotemporal magnetic phenomena that are relevant to future high-speed, high-density magnetic storage and logic technologies. Magnetic microscopes that combine these metrics has been limited to facility-level instruments. To address this gap in lab-accessible spatiotemporal imaging, we develop a time-resolved near-field magnetic microscope based on magnetothermal interactions. We demonstrate both magnetization and current density imaging modalities, each with spatial resolution that far surpasses the optical diffraction limit. In addition, we study the near-field and time-resolved characteristics of our signal and find that our instrument possesses a spatial resolution on the scale of 100 nm and a temporal resolution below 100 ps. Our results demonstrate an accessible and comparatively low-cost approach to nanoscale spatiotemporal magnetic microscopy in a table-top form to aid the science and technology of dynamic magnetic devices with complex spin textures.
Data from: Thermal transport of helium-3 in a strongly confining channel
Lotnyk, Dmytro; Eyal, Anna; Zhelev, Nikolay; Sebastian, Abhilash; Smith, Eric; Terilli, Michael; Wilson, John; Mueller, Erich; Einzel, Dietrich; Saunders, John; Parpia, Jeevak (2020-09-24)
The investigation of transport properties in normal liquid helium-3 and its topological superfluid phases provides insights into related phenomena in electron fluids, topological materials, and putative topological superconductors. It relies on the measurement of mass, heat, and spin currents, due to system neutrality. Of particular interest is transport in strongly confining channels of height approaching the superfluid coherence length, to enhance the relative contribution of surface excitations, and suppress hydrodynamic counter-flow. Here we report on the thermal conduction of helium-3 in a 1.1 um high channel. The experiment was carried out by locally heating one chamber and by measuring the flow of energy out of that chamber. Figure 2) In the normal state (Figures 3, 4 and Supplemental Figures 6, 7) we observe a diffusive thermal conductivity that is approximately temperature independent, consistent with interference of bulk and boundary scattering. In the superfluid, the thermal conductivity is only weakly temperature dependent (Figure 5), requiring detailed theoretical analysis. An anomalous thermal response is detected in the superfluid (Figures 6, 7 and Supplemental Figures 2, 3, 4) which we propose arises from the emission of a flux of surface excitations from the channel. Supplemental Figure 1 summarizes calculations that show that the anomalous heat transport cannot arise from normal-superfluid counterflow. In this package we provide the data set was used to plot the figures so that digitization is not needed and the data may be used for comparison in future works.
The A-B transition in superfluid 3He under confinement in a thin slab geometry
Zhelev, Nikolay; Abhilash, Thanniyil Sebastian; Smith, Eric; Bennett, Robert; Rojas, Xavier; Levitin, Lev; Saunders, John; Parpia, Jeevak (2017)
The influence of confinement on the topological phases of superfluid 3He is studied using the torsional pendulum method. We focus on the phase transition between the chiral A-phase and the time-reversal-invariant B-phase, motivated by the prediction of a spatially-modulated (stripe) phase at the A-B phase boundary. We confine superfluid 3He to a single 1.08 μm thick nanofluidic cavity incorporated into a high-precision torsion pendulum, and study the pressure dependence of the phase diagram between 0.1 and 5.6 bar. We observe only small supercooling of the A-phase, in comparison to bulk or when confined in aerogel. This has a non-monotonic pressure dependence, suggesting that a new intrinsic B-phase nucleation mechanism operates under confinement, mediated by the putative stripe phase. Both the pressure dependence of the phase diagram and the relative superfluid fraction of the A and B phases, show that strong coupling is present at all pressures, with implications for the stability of the stripe phase.

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