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1. Building a Casimir Metrology Platform with a commercial MEMS sensor

   https://doi.org/https://doi.org/10.1038/s41378-019-0054-5  

   Stange, A. ; Imboden, M. ; Javor, J. ; Barrett, L. ; Bishop, D. ( April 2019 , 07 Nature)

   The Casimir Effect is a physical manifestation of quantum fluctuations of the electromagnetic vacuum. When two metal plates are placed close together, typically much less than a micron, the long wavelength modes between them are frozen out, giving rise to a net attractive force between the plates, scaling as d−4 (or d−3 for a spherical-planar geometry) even when they are not electrically charged. In this paper, we observe the Casimir Effect in ambient conditions using a modified capacitive micro-electromechanical system (MEMS) sensor. Using a feedback-assisted pick-and-place assembly process, we are able to attach various microstructures onto the post-release MEMS, converting it from an inertial force sensor to a direct force measurement platform with pN (piconewton) resolution. With this system we are able to directly measure the Casimir force between a silver-coated microsphere and gold-coated silicon plate. This device is a step towards leveraging the Casimir Effect for cheap, sensitive, room temperature quantum metrology. 

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2. Building a Casimir Metrology Platform with a Commercial MEMS Sensor

   Stange, A. ; Imboden, M. ; Javor, J. ; Barrett, L. ; Bishop, D ( April 2019 , 07 Nature)

   The Casimir Effect is a physical manifestation of quantum fluctuations of the electromagnetic vacuum. When two metal plates are placed close together, typically much less than a micron, the long wavelength modes between them are frozen out, giving rise to a net attractive force between the plates, scaling as d−4 (or d−3 for a spherical-planar geometry) even when they are not electrically charged. In this paper, we observe the Casimir Effect in ambient conditions using a modified capacitive micro-electromechanical system (MEMS) sensor. Using a feedback-assisted pick-and-place assembly process, we are able to attach various microstructures onto the post-release MEMS, converting it from an inertial force sensor to a direct force measurement platform with pN (piconewton) resolution. With this system we are able to directly measure the Casimir force between a silver-coated microsphere and gold-coated silicon plate. This device is a step towards leveraging the Casimir Effect for cheap, sensitive, room temperature quantum metrology. 

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3. AFM dilatometry measurements on ultra‐stable fluoropolymer glasses: Further evidence of extreme fictive temperature reduction

   https://doi.org/10.1002/pol.20230478  

   El Banna, Amer A. ; McKenna, Gregory B. ( October 2023 , Journal of Polymer Science)

   Ultra‐stable amorphous fluoropolymers glasses were created using vacuum pyrolysis deposition (VPD). Glass films with thickness ranging from 90 to 160 nm were grown at a substrate temperature of 0.86T_g, whereT_gis the glass transition temperature of the virgin polymer and is in units of K. Atomic force microscope (AFM) dilatometry measurements were conducted to investigate density behavior of the ultra‐stable glasses. Thickness measurements were made in stepwise fashion over a range of temperatures from ambient to above theT_g. Results show that the intersections of the line for the equilibrium liquid and those for the rejuvenated and stable glasses identifying the fictive temperatureT_fresult inT_{f, rejuvenated} = 347.3 K andT_{f, stable} = 269.5 K, that is, nearly 80 K below theT_gof the rejuvenated material and well below the notional Kauzmann temperature as estimated from the Vogel‐Fultcher‐Tammann (VFT) analysis of the cooling rate dependence of the calorimetric glass transition temperature reported previously. The results corroborate the published calorimetric results on the same ultra‐stable fluoropolymer glasses that witnessedT_freductions of up to 62.6 K below theT_gof the rejuvenated system. In addition, to demonstrate the versatility of the AFM dilatometry methodology for the thin film response, isothermal de‐aging experiments were carried out to illustrate the devitrification kinetics. We also carried out one of the Kovacs’ signature key experiments, the asymmetry of approach, to further illustrate the method.

    

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4. Superconductivity from energy fluctuations in dilute quantum critical polar metals

   https://doi.org/10.1038/s41467-022-32303-2  

   Volkov, Pavel A. ; Chandra, Premala ; Coleman, Piers ( August 2022 , Nature Communications)

   Superconductivity in low carrier density metals challenges the conventional electron-phonon theory due to the absence of retardation required to overcome Coulomb repulsion. Here we demonstrate that pairing mediated by energy fluctuations, ubiquitously present close to continuous phase transitions, occurs in dilute quantum critical polar metals and results in a dome-like dependence of the superconductingT_con carrier density, characteristic of non-BCS superconductors. In quantum critical polar metals, the Coulomb repulsion is heavily screened, while the critical transverse optical phonons decouple from the electron charge. In the resulting vacuum, long-range attractive interactions emerge from the energy fluctuations of the critical phonons, resembling the gravitational interactions of a chargeless dark matter universe. Our estimates show that this mechanism may explain the critical temperatures observed in doped SrTiO₃. We provide predictions for the enhancement of superconductivity near polar quantum criticality in two- and three-dimensional materials that can be used to test our theory.

    

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5. Electrodynamic Force, Casimir Effect, and Stiction Mitigation in Silicon Carbide Nanoelectromechanical Switches

   https://doi.org/10.1002/smll.202005594  

   Yang, Rui ; Qian, Jiang ; Feng, Philip X. ‐L. ( November 2020 , Small)

   Logic switches enabled by nanoelectromechanical systems (NEMS) offer abrupt on/off‐state transition with zero off‐state leakage and minimal subthreshold swing, making them uniquely suited for enhancing mainstream electronics in a range of applications, such as power gating, high‐temperature and high‐voltage logic, and ultralow‐power circuits requiring zero standby leakage. As NEMS switches are scaled with genuinely nanoscale gaps and contacts, quantum mechanical electrodynamic force (EDF) takes an important role and may be the ultimate cause of the plaguing problem of stiction. Here, combined with experiments on three‐terminal silicon carbide (SiC) NEMS switches, a theoretical investigation is performed to elucidate the origin of EDF and Casimir effect leading to stiction, and to develop a stiction‐mitigation design. The EDF calculation with full Lifshitz formula using the actual material and device parameters is provided. Finite element modeling and analytical calculations demonstrate that EDF becomes dominant over elastic restoring force in such SiC NEMS when the switching gap shrinks to a few nanometers, leading to irreversible stiction at contact. Artificially corrugated contact surfaces are designed to reduce the contact area and the EDF, thus evading stiction. This rationalsurface engineeringreduces the EDF down to 4% compared with the case of unengineered, flat contact surfaces.

    

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