arXiv subjects

Brian D'Urso

Publications and source records attributed to Brian D'Urso.

16 recordsLinked to original sources

arXiv2026

Ultra-low damping of the translational motion of a composite graphite rod in a magneto-gravitational trap

We demonstrate an ultra-low dissipation, one-dimensional mechanical oscillator formed by levitating a millimeter-scale composite graphite rod in a room-temperature magneto-gravitational trap. The trap's magnetic field geometry, based on a linear quadrupole, eliminates first-order field gradients in the axial direction, yielding a low oscillation frequency with ultra-low eddy-current losses. Direct ring-down measurements under vacuum compare the damping of the vertical and axial motion; while the vertical motion damps in seconds, the axial motion damps with a time constant of over 5 days. Analysis reveals that this dramatic difference in damping is a result of the symmetry of the magnetic field and the anisotropy of the trap strength. The results are remarkably robust, demonstrating a potential platform for inertial and gravitational sensing.

physics.app-ph↗

arXiv2024

Cross-correlation image analysis for real-time particle tracking

Accurately measuring the translations of objects between images is essential in many fields, including biology, medicine, chemistry, and physics. One important application is tracking one or more particles by measuring their apparent displacements in a series of images. Popular methods, such as the center-of-mass, often require idealized scenarios to reach the shot-noise limit of particle tracking and are, therefore, not generally applicable to multiple image types. More general methods, like maximum likelihood estimation, reliably approach the shot-noise limit, but are too computationally intense for use in real-time applications. These limitations are significant, as real-time, shot-noise-limited particle tracking is of paramount importance for feedback control systems. To fill this gap, we introduce a new cross-correlation-based algorithm that approaches shot-noise-limited displacement detection and a GPU-based implementation for real-time image analysis of a single particle.

physics.optics↗

arXiv2024

Selective Loading of a Micrometer-Scale Particle into a Magneto-Gravitational Trap by Sublimation-Activated Release

In this paper we discuss a technique for selectively loading a particle into a magneto-gravitational trap using the sublimation of camphor to release particles from a tungsten probe tip directly into the trapping region. This sublimation-activated release (SAR) loading technique makes use of micropositioners with tungsten probe tips, as well as the relatively fast rate of sublimation of camphor at room temperature, to selectively load particles having diameters ranging from $\SI{8}{\micro \meter}$ to $\SI{100}{\micro \meter}$ or more. The advantages of this method include its ability to selectively load unique particles or particles in limited supply, its low loss compared to alternative techniques, the low speed of the particle when released, and the versatility of its design which allows for loading into traps with complex geometries. SAR is demonstrated here by loading a particle into a magneto-gravitational trap, but the technique could also be applicable to other levitated optomechanical systems.

physics.app-ph↗

arXiv2024

Lessons from Transforming Second-Year Honors Physics Lab

New technology like the Arduino microcontroller platform presents an opportunity to transform Beyond the First Year (BFY) physics labs to better prepare physics students for work in research labs and beyond. The flexibility, low cost, and power of these devices provides an attractive way for students to learn to use and master research-grade instrumentation. Therefore, we introduced new technology, including Arduino Due microcontroller boards, to a second-year honors physics lab in order to provide improved learning experiences for students. This transformation was implemented in three lab modules and focused on diminishing the black box nature of the traditional labs while encouraging students to engage in troubleshooting. The importance of troubleshooting was made evident to students by the instructor emphasizing it as an inevitable and central part of experimentation. This lab transformation also required that students perform work that was `above and beyond' the scope of the assigned experimental work for part of the course credit. While the technological aspects of the transformation were received well by a majority of students, our observations during the initial implementation suggested a need for some modifications to instructional practices in order to improve the learning and experiences for all students. In particular, we find that many students can benefit from additional scaffolding in order to complete `above and beyond' work. Similarly, we find that students in general, and underrepresented students such as women in particular, may need thoughtful intervention from the instructor, e.g., in order to avoid becoming isolated when the lab work is designed for pair work. Otherwise, some students may be left to work alone with a disproportionate work-load if students choose their own partners.

physics.ed-ph↗

arXiv2020

Active Optical Table Tilt Stabilization

We show that a simple modification to an optical table with pneumatic vibration isolation can be used to actively reduce the long term drift in the tilt of the table by nearly a factor of 1000. Without active stabilization, we measure a root-mean-square (RMS) tilt variation of \SI{270}{\upmu rad} over three days. The active stabilization can be used to limit the tilt to \SI{0.35}{\upmu rad} RMS over the same time period. This technique can be used to minimize drift in tilt-sensitive experiments.

physics.ins-det↗

arXiv2020

High sensitivity accelerometry with a feedback-cooled magnetically levitated microsphere

We show that a magnetically levitated microsphere in high vacuum can be used as an accelerometer by comparing its response to that of a commercially available geophone. This system shows great promise for ultrahigh acceleration sensitivities without the need for large masses or cryogenics. With feedback cooling, the transient decay time is reduced and the center-of-mass motion is cooled to \SI{9}{K} or less. Remarkably, the levitated particle accelerometer has a sensitivity down to \SI{3.6e-8}{\mathit{g}/\sqrt{Hz}} and gives measurements similar to those of the commercial geophone at frequencies up to \SI{14}{Hz} despite a test mass that is four billion times smaller. With no free parameters in the calibration, the responses of the accelerometers match within \num{3}\% at \SI{5}{Hz}. The system reaches this sensitivity due to a relatively large particle mass of \SI{0.25}{\upmu g}, a low center of mass oscillation frequency of \SI{1.75}{Hz}, and a novel image analysis method that can measure the displacement with an uncertainty of \SI{1.6}{nm} in a single image.

physics.app-ph↗

arXiv2019

Reconfigurable edge-state engineering in graphene using LaAlO$_3$/SrTiO$_3$ nanostructures

The properties of graphene depend sensitively on doping with respect to the charge-neutrality point (CNP). Tuning the CNP usually requires electrical gating or chemical doping. Here, we describe a technique to reversibly control the CNP in graphene with nanoscale precision, utilizing LaAlO$_3$/SrTiO$_3$ (LAO/STO) heterostructures and conductive atomic force microscope (c-AFM) lithography. The local electron density and resulting conductivity of the LAO/STO interface can be patterned with a conductive AFM tip, and placed within two nanometers of an active graphene device. The proximal LAO/STO nanostructures shift the position of graphene CNP by ~ $10^{12}$ cm$^{-2}$, and are also gateable. Here we use this effect to create reconfigurable edge states in graphene, which are probed using the quantum Hall effect. Quantized resistance plateaus at $h/e^2$ and $h/3e^2$ are observed in a split Hall device, demonstrating edge transport along the c-AFM written edge that depends on the polarity of both the magnetic field and direction of currents. This technique can be readily extended to other device geometries.

cond-mat.mes-hall↗

arXiv2018

Cooling the Motion of a Silica Microsphere in a Magneto-Gravitational Trap in Ultra-High Vacuum

Levitated optomechanical systems, and particularly particles trapped in vacuum, provide unique platforms for studying the mechanical behavior of objects well-isolated from their environment. Ultimately, such systems may enable the study of fundamental questions in quantum mechanics, gravity, and other weak forces. While the optical trapping of nanoparticles has emerged as the prototypical levitated optomechanical system, it is not without problems due to the heating from the high optical intensity required, particularly when combined with a high vacuum environment. Here we investigate a magneto-gravitational trap in ultra-high vacuum. In contrast to optical trapping, we create an entirely passive trap for diamagnetic particles by utilizing the magnetic field generated by permanent magnets and the gravitational interaction. We demonstrate cooling the center of mass motion of a trapped silica microsphere from ambient temperature to an effective temperature near or below one milliKelvin in two degrees of freedom by optical feedback damping.

quant-ph↗

arXiv2016

Room-temperature quantum transport signatures in graphene/LaAlO3/SrTiO3 heterostructures

The pseudospin quantum degree of freedom is one of the most remarkable properties of graphene that distinguishes it from ordinary two-dimensional metals and semiconductors. Pseudospin quantum interference leads to weak antilocalization (WAL) and is influenced strongly by point defects and thermal perturbations that break chirality and destroy phase coherence. Preserving and manipulating quantum transport properties up to room temperature is key to realizing practical pseudospin-based graphene devices. Here we report fabrication and transport characterization of graphene field-effect devices on a complex-oxide heterostructure, LaAlO3/SrTiO3. Signatures of WAL, a consequence of pseudospin quantum interference, persist up to room temperature. The LaAlO3/SrTiO3 substrate plays a critical role in suppressing short-range impurity scattering and electron-phonon coupling. The observation of quantum transport signatures at room temperature is unique to this system and presents new opportunities for the development of pseudospin-based devices and novel multifunctional devices that couple to the complex-oxide interface.

cond-mat.mes-hall↗

arXiv2016

Method for Transferring High-Mobility CVD-Grown Graphene with Perfluoropolymers

The transfer of graphene grown by chemical vapor deposition (CVD) using amorphous polymers represents a widely implemented method for graphene-based electronic device fabrication. However, the most commonly used polymer, poly(methyl methacrylate) (PMMA), leaves a residue on the graphene that limits the mobility. Here we report a method for graphene transfer and patterning that employs a perfluoropolymer---Hyflon---as a transfer handle and to protect graphene against contamination from photoresists or other polymers. CVD-grown graphene transferred this way onto LaAlO$_3$/SrTiO$_3$ heterostructures is atomically clean, with high mobility (~30,000 cm$^2$V$^{-1}$s$^{-1}$) near the Dirac point at 2 K and clear, quantized Hall and magneto-resistance. Local control of the LaAlO$_3$/SrTiO$_3$ interfacial metal-insulator transition---through the graphene---is preserved with this transfer method. The use of perfluoropolymers such as Hyflon with CVD-grown graphene and other 2D materials can readily be implemented with other polymers or photoresists.

cond-mat.mtrl-sci↗

arXiv2016

Nitrogen vacancy centers in diamond as angle-squared sensors

Nitrogen-vacancy (NV) centers are defects in diamonds, which, due to their electronic structure, have been extensively studied as magnetic field sensors. Such field detection applications usually employ the NV centers to detect field components aligned with the direction of the internally-defined spin axis of the NV center. In this work we detect magnetic fields which are slightly misaligned with the NV center axis. In particular, we demonstrate that the NV center can measure the square of the angle between the magnetic field and the NV center axis with high sensitivity which diverges as the external field approaches a value pre-defined by NV center's internal parameters, in agreement with predictions. These results show that NV centers could be used as sensitive transducers for making quantum nondemolition (QND) measurements on systems such as nanomechanical oscillators.

quant-ph↗

arXiv2016

Cooling the Motion of Diamond Nanocrystals in a Magneto-Gravitational Trap in High Vacuum

Levitated diamond nanocrystals with nitrogen-vacancy (NV) centres in high vacuum have been proposed as a unique system for experiments in fundamental quantum mechanics, including the generation of large quantum superposition states and tests of quantum gravity. This system promises extreme isolation from its environment while providing quantum control and sensing through the NV centre spin. While optical trapping has been the most explored method of levitation, recent results indicate that excessive optical heating of the nanodiamonds under vacuum may make the method impractical with currently available materials. Here, we study an alternative magneto-gravitational trap for diamagnetic particles, such as diamond nanocrystals, with stable levitation from atmospheric pressure to high vacuum. Magnetic field gradients from permanent magnets confine the particle in two dimensions, while confinement in the third dimension is gravitational. We demonstrate that feedback cooling of the centre-of-mass motion of a trapped nanodiamond cluster results in cooling of one degree of freedom to less than 1 K.

quant-ph↗

arXiv2016

Formation of hexagonal Boron Nitride on Graphene-covered Copper Surfaces

Graphene-covered copper surfaces have been exposed to borazine, (BH)3(NH)3, with the resulting surfaces characterized by low-energy electron microscopy. Although the intent of the experiment was to form hexagonal boron nitride (h-BN) on top of the graphene, such layers were not obtained. Rather, in isolated surface areas, h-BN is found to form micrometer-size islands that substitute for the graphene. Additionally, over nearly the entire surface, the properties of the layer that was originally graphene is observed to change in a manner that is consistent with the formation of a mixed h-BN/graphene alloy, i.e. h-BNC alloy. Furthermore, following the deposition of the borazine, a small fraction of the surface is found to consist of bare copper, indicating etching of the overlying graphene. The inability to form h-BN layers on top of graphene is discussed in terms of the catalytic behavior of the underlying copper surface and the decomposition of the borazine on top of the graphene.

cond-mat.mtrl-sci↗

arXiv2015

Stability of Superhydrophobic Ring & Axle Liquid Bearings

Friction between contacting solid surfaces is a dominant force on the micro-scale and a major consideration in the design of MEMS. Non-contact fluid bearings have been investigated as a way to mitigate this issue. Here we discuss a new design for surface tension-supported thrust bearings utilizing patterned superhydrophobic surfaces to achieve improved drag reduction. We examine sources of instability in the design, and demonstrate that it can be simply modeled and has superior stiffness as compared to other designs.

cond-mat.soft↗

arXiv2015

Absolute Measurement Of Laminar Shear Rate Using Photon Correlation Spectroscopy

An absolute measurement of the components of the shear rate tensor $\mathcal{S}$ in a fluid can be found by measuring the photon correlation function of light scattered from particles in the fluid. Previous methods of measuring $\mathcal{S}$ involve reading the velocity at various points and extrapolating the shear, which can be time consuming and is limited in its ability to examine small spatial scale or short time events. Previous work in Photon Correlation Spectroscopy has involved only approximate solutions, requiring free parameters to be scaled by a known case, or different cases, such as 2-D flows, but here we present a treatment that provides quantitative results directly and without calibration for full 3-D flow. We demonstrate this treatment experimentally with a cone and plate rheometer.

cond-mat.soft↗

arXiv2014

Large Drag Reduction over Superhydrophobic Riblets

Riblets and superhydrophobic surfaces are two demonstrated passive drag reduction techniques. We describe a method to fabricate surfaces that combine both of these techniques in order to increase drag reduction properties. Samples have been tested with a cone-and-plate rheometer system, and have demonstrated significant drag reduction even in the transitional-turbulent regime. Direct Numerical Simulations have been performed in order to estimate the equivalent slip length at higher rotational speed. The sample with 100~$μ$m deep grooves has been performing very well, showing drag reduction varying from 15 to 20 $\%$ over the whole range of flow conditions tested, and its slip length was estimated to be over 100 $μ$m.

physics.flu-dyn↗