Yuki Sato

Harvard University, Cambridge, Massachusetts, United States

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Publications (25)102.55 Total impact

  • Yuki Sato
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    ABSTRACT: L'effet Sagnac a joué un rôle déterminant dans les études fondamentales en relativité, et les dispositifs utilisant cet effet ont trouvé des applications dans des disciplines variées allant, de la navigation inertielle à la géodésie et à la sismologie. Dans ce contexte, nous présentons un aperçu de l'évolution récente des dispositifs d'interférence quantique dans l'hélium superfluide. Avec la découverte de l'effet Josephson dans l'hélium 4 superfluide, cette technologie s'est rapidement développée au cours des dix dernières années. Nous discutons ici les principes sous-jacents à ces dispositifs d'interférences et leurs applications. Nous nous concentrons sur leur utilisation en tant que capteurs de rotation fondés sur l'effet Sagnac couplée avec l'existence d'une phase quantique macroscopique via la dualité particule–onde.
    Comptes Rendus Physique 12/2014; DOI:10.1016/j.crhy.2014.10.004 · 1.64 Impact Factor
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    ABSTRACT: We demonstrate an innovative multifunctional artificial material that combines exotic metamaterial properties and the environmentally responsive nature of phase change media. The tunable metamaterial is designed with the aid of two interwoven coordinate-transformation equations and implemented with a network of thin film resistors and vanadium dioxide ($VO_{2}$). The strong temperature dependence of $VO_{2}$ electrical conductivity results in a relevant modification of the resistor network behavior, and we provide experimental evidence for a reconfigurable metamaterial electric circuit (MMEC) that not only mimics a continuous medium but is also capable of responding to thermal stimulation through dynamic variation of its spatial anisotropy. Upon external temperature change the overall effective functionality of the material switches between a "truncated-cloak" and "concentrator" for electric currents. Possible applications may include adaptive matching resistor networks, multifunctional electronic devices, and equivalent artificial materials in the magnetic domain. Additionally, the proposed technology could also be relevant for thermal management of integrated circuits
    Physical Review B 05/2014; 91(13). DOI:10.1103/PhysRevB.91.134105 · 3.66 Impact Factor
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    ABSTRACT: Spatial tailoring of the material constitutive properties is a well-known strategy to mold the local flow of given observables in different physical domains. Coordinate-transformation-based methods (e.g., transformation optics) offer a powerful and systematic approach to design anisotropic, spatially inhomogeneous artificial materials (metamaterials) capable of precisely manipulating wave-based (electromagnetic, acoustic, elastic) as well as diffusion-based (heat) phenomena in a desired fashion. However, as versatile as these approaches have been, most designs have thus far been limited to serving single-target functionalities in a given physical domain. Here, we present a step towards a “transformation multiphysics” framework that allows independent and simultaneous manipulation of multiple physical phenomena. As a proof of principle of this new scheme, we design and synthesize (in terms of realistic material constituents) a metamaterial shell that simultaneously behaves as a thermal concentrator and an electrical “invisibility cloak.” Our numerical results open up intriguing possibilities in the largely unexplored phase space of multifunctional metadevices, with a wide variety of potential applications to electrical, magnetic, acoustic, and thermal scenarios.
    Physical Review X 05/2014; 4(2):021025. DOI:10.1103/PhysRevX.4.021025 · 8.39 Impact Factor
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    ABSTRACT: Spatial tailoring of the material constitutive properties is a well-known strategy to mold the local flow of given observables in different physical domains. Coordinate-transformation-based methods (e.g., transformation optics) offer a powerful and systematic approach to design anisotropic, spatially-inhomogeneous artificial materials ("metamaterials") capable of precisely manipulating wave-based (electromagnetic, acoustic, elastic) as well as diffusion-based (heat) phenomena in a desired fashion. Most studies available in the literature deal with the design of a single specific functionality in a given physical domain. We address here the simultaneous manipulation of multiple physical phenomena in independent fashions. As a proof of principle of this "transformation multiphysics" framework, we design and synthesize (in terms of realistic material constituents) a metamaterial shell that simultaneously behaves as a thermal concentrator and an electrical "invisibility cloak". Our numerical results open up intriguing possibilities in the largely unexplored phase space of multi-functional metastructures, with a wide variety of potential applications to electrical, magnetic, acoustic, and thermal scenarios.
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    ABSTRACT: We have developed a heat shield based on a metamaterial engineering approach to shield a region from transient diffusive heat flow. The shield is designed with a multilayered structure to prescribe the appropriate spatial profile for heat capacity, density, and thermal conductivity of the effective medium. The heat shield was experimentally compared to other isotropic materials.
    Applied Physics Letters 05/2013; 102(20). DOI:10.1063/1.4807744 · 3.52 Impact Factor
  • Yuki Sato, Richard Packard
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    ABSTRACT: The development of superfluid weak links has led both to the discovery of new physical phenomena and also to the development of superfluid helium quantum interference devices (SHeQUIDs). We describe the physics underlying the SHeQUID and present a brief overview of the current state of this promising technology.
    Journal of Physics Conference Series 12/2012; 400(5):2030-. DOI:10.1088/1742-6596/400/5/052030
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    Supradeep Narayana, Yuki Sato
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    ABSTRACT: Utilizing a multilayered composite approach, we have designed and constructed a new class of artificial materials for thermal conduction. We show that an engineered material can be utilized to control the diffusive heat flow in ways inconceivable with naturally occurring materials. By shielding, concentrating, and inverting heat current, we experimentally demonstrate the unique potential and the utility of guiding heat flux. Thermodynamics is a well-established discipline in sci-ence, and the concept of heat has been known for a long time. That often makes us forget how difficult it really is to manipulate heat flow in real life. Compared to the field of electric conduction armed with nonlinear solid-sate de-vices, heat conduction management is still in its infancy. The ability to precisely control heat current has significant implications beyond scientific curiosity, and can poten-tially lead to the development of thermal analogues of electronic transistors, rectifiers, and diodes. Here we show that an artificial material can be utilized to guide the heat flow in ways inconceivable with naturally occur-ring materials. We demonstrate this concept by engineer-ing a new class of artificial material for thermal conduction and experimentally shielding, concentrating, and inverting the applied heat flux. The results constitute a vivid dem-onstration of extreme heat flux control with artificial ma-terials and provide a conceptual insight that heat current, like electric and photonic current, should be viewed as a medium that can be manipulated, controlled, and processed. The ability to manipulate the path of energy propagation is a trait that distinguishes artificial materials from ordinary materials. In a solid material supporting heat current, the properties induced from artificially arranged thermal con-ductivities can be counterintuitive. Although some theo-retical work including the prediction of a thermal cloak has been carried out [1–3], such thermal ''meta''-materials have, so far, not been investigated experimentally. We first discuss the shielding operation and then proceed to con-centrating and inverting heat flux. See Fig. 1(a). When a block of material is placed between a heat source and a sink, a uniform temperature gradient is established across the material. Heat current flows from left to right as indicated by the arrows. Figure 1(b) depicts the same block with a hollow cylindrical shield inserted at the center. Here we require the exterior region to exhibit the same temperature profile as Fig. 1(a) without the shield, while the interior region now needs to have no temperature gradient. To gain control over the path of energy transport via thermal conduction, one needs to engineer an artificial material with prescribed anisotropy in its thermal conduc-tivity. One of the most practical ways to introduce such anisotropy is to build a stacked composite from macro-scopic layers of isotropic materials. Consider, for example, a composite made of alternating sheets of materials A and B. In a perpendicular direction, the two alternating con-ductances add in series, while they add in parallel in a transverse direction. Thus, the overall thermal conductivity of the effective medium becomes anisotropic, and the heat flux density vector changes direction as it propagates through the material. Building on this effect, one can design and assemble an artificial composite material that forces the heat flux to follow a particular path of interest. A concentric layered structure consisting of alternating layers of materials A and B of different homogeneous isotropic thermal conductivities A and B is depicted in Fig. 2(a). For the host background material, we use a 5% agar-water block with thermal conductivity h $ 0:56 W=ðmKÞ [4]. For the device to blend into the back-ground thermally and not perturb the external field profile, the thermal resistance of the host material should be close to the reduced average of those of the two
    Physical Review Letters 05/2012; 108(214303). DOI:10.1103/PhysRevLett.108.214303 · 7.73 Impact Factor
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    Supradeep Narayana, Yuki Sato
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    ABSTRACT: Utilizing a non-resonant graded material consisting of an array of artificially patterned superconducting and soft ferromagnetic elements, we construct a dc magnetic cloak. When an external dc magnetic field is applied, we find that the interior of the cloak is completely shielded while the exterior field remains unperturbed, as if the cloak and the cloaked region are just an empty space.
    Advanced Materials 01/2012; 24(1):71-4. DOI:10.1002/adma.201104012 · 15.41 Impact Factor
  • Yuki Sato, Richard Packard
    Physics Today 01/2012; 65(10):31-. DOI:10.1063/PT.3.1749 · 5.89 Impact Factor
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    Supradeep Narayana, Yuki Sato
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    ABSTRACT: We report the observation of superfluid quantum interference in a compact, large-area matter-wave interferometer consisting of a multiple-turn interfering path in reciprocal geometry. Utilizing the Sagnac effect from Earth's rotation in conjunction with a phase shifter made of superfluid heat current, we demonstrate that such a scheme can be extended for sensitive rotation sensing as well as for general interferometry.
    Physical Review Letters 06/2011; 106(25):255301. DOI:10.1103/PHYSREVLETT.106.255301 · 7.73 Impact Factor
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    Supradeep Narayana, Yuki Sato
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    ABSTRACT: We report a new kind of experiment in which we take an array of nanoscale apertures that form a superfluid (4)He Josephson junction and apply quantum phase gradients directly along the array. We observe collective coherent behaviors from aperture elements, leading to quantum interference. Connections to superconducting and Bose-Einstein condensate Josephson junctions as well as phase coherence among the superfluid aperture array are discussed.
    Physical Review Letters 02/2011; 106(5):055302. DOI:10.1103/PhysRevLett.106.055302 · 7.73 Impact Factor
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    Supradeep Narayana, Yuki Sato
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    ABSTRACT: We report a compact miniature high-resolution thermometer (CMHRT) based on dilute paramagnetic alloy of PdMn and commercially available Neodymium (NdFeB) magnets. The thermometer utilizes the temperature dependence of magnetic susceptibility of the alloy in an applied magnetic field. The change in susceptibility is measured with a pickup coil connected to a dc-SQUID. Based on this approach, we have developed a self-contained thermometer with sub-nanoKelvin sensitivity with the operating temperature range of 1.6-4 K. Its design, assembly, and performance are described.
    IEEE Transactions on Applied Superconductivity 01/2011; DOI:10.1109/TASC.2010.2087021 · 1.32 Impact Factor
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    Yuki Sato, Richard Packard
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    ABSTRACT: We show through numerical simulations that absolute quantum mechanical phase differences could be observed using an asymmetric superfluid quantum interference grating. By balancing the dynamic range and the degree of change required per period in an interference pattern, a device could be optimized and used to probe heretofore inaccessible quantum subtleties. We make connections to experimental results and discuss possible applications for such systems.
    Physica E Low-dimensional Systems and Nanostructures 01/2011; 43(3):702-706. DOI:10.1016/j.physe.2010.07.033 · 1.86 Impact Factor
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    Supradeep Narayana, Yuki Sato
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    ABSTRACT: We report a direct observation of dynamical bifurcation between two plasma oscillation states of a superfluid Josephson junction. We excite the superfluid plasma resonance into a nonlinear regime by driving below the natural plasma frequency and observe a clear transition between two dynamical states. We also demonstrate bifurcation by changing the potential well with temperature variations.
    Physical Review Letters 11/2010; 105(20):205302. DOI:10.1103/PhysRevLett.105.205302 · 7.73 Impact Factor
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    Yuki Sato, Richard Packard
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    ABSTRACT: A new displacement sensor that uses a rare-earth magnet attached to a flexible diaphragm is demonstrated for superfluid experiments. Its construction, calibration, and performance are described.
    The Review of scientific instruments 06/2009; 80(5):055102. DOI:10.1063/1.3129942 · 1.58 Impact Factor
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    ABSTRACT: We describe an experiment in which we induce a heat-driven superfluid flow in a straight tube and monitor the phase difference across the tube's ends with a superfluid 4He quantum interference device (SHeQUID). We quantitatively verify the relation υs = (/m) ∇ . We also demonstrate the linearization of a SHeQUID using the heat injection method.
    Journal of Physics Conference Series 03/2009; 150(3):032092. DOI:10.1088/1742-6596/150/3/032092
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    Yuki Sato, Richard Packard
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    ABSTRACT: It has been predicted that, in the presence of combined radial electric field and axial magnetic field, superfluid 4 He in a torus will have a persistent current in its ground state. This surprising result arises from non-cancellation of the Aharonov-Bohm phase shifts associated with the opposite charges in the induced electric dipole moment of the neutral 4 He atoms. We briefly review this prediction and describe our proposed experiment. In this feasibility study we show that by applying laboratory accessible electric and magnetic fields, a superfluid 4 He interferometer (SHeQUID) will have sufficient sensitivity to conclusively determine whether or not the predicted physical phenomenon exists.
    Journal of Physics Conference Series 02/2009; 150(3). DOI:10.1088/1742-6596/150/3/032093
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    ABSTRACT: Arrays of nanoscale apertures have been found to exhibit fascinating quantum phenomena such as the Josephson effect and collective quantized phase-slippage. To be in the Josephson regime, the aperture size must be comparable to the healing length of the 4 He order parameter. For 50nm apertures this regime is attained ∼mK below T λ . Collective phase slippage occurs at considerably lower temperatures. Fabricating aperture arrays with appropriate properties (strength, temporal stability and reproducibility) at these length scales has been a long-standing goal for our group. Here, we present the techniques used thus far, based on recent work performed at the Cornell Nanoscale Facility. We discuss some issues that arise and their possible solutions.
    Journal of Physics Conference Series 02/2009; 150(1). DOI:10.1088/1742-6596/150/1/012018
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    ABSTRACT: We report the first observation of quantum interference from a grating structure consisting of four weak link junctions in superfluid 4He. We find that an interference grating can be implemented successfully in a superfluid matter wave interferometer to enhance its sensitivity while trading away some of its dynamic range. We also show that this type of device can be used to measure absolute quantum mechanical phase differences. The results demonstrate the robust nature of superfluid phase coherence arising from quantum mechanics on a macroscopic scale.
    Physical Review Letters 09/2008; 101(8):085302. DOI:10.1103/PHYSREVLETT.101.085302 · 7.73 Impact Factor
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    ABSTRACT: To understand the origins of synchronous and asynchronous phase slippages observed in an array of apertures connecting two reservoirs of superfluid 4He, we have investigated the role of thermal fluctuations in the critical velocity and the possible effects of having an array rather than a single aperture through several model simulations. The results are compared with recent experiments carried out near the superfluid transition temperature with an array of apertures as well as those carried out at low temperatures with a single aperture.
    Journal of Low Temperature Physics 11/2007; 149(5):222-229. DOI:10.1007/s10909-007-9510-y · 1.04 Impact Factor