News

Superfluid quantum interference in multiple-turn reciprocal geometry

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 the 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 106, 255301 (2011).

International Conference on Low Temperature Physics

26th International Conference on Low Temperature Physics will be held in Beijing, China (8/10/11-8/17/11), followed by its satellite conference, 2011 International Conference on Ultra Low Temperature Physics in Daejeon, Korea (8/19/11-8/22/11).

Quantum coherence in a superfluid Josephson junction

We report a new kind of experiment in which we take an array of nanoscale apertures that form a superfluid 4He 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 BEC Josephson junctions as well as phase coherence among the superfluid aperture array are discussed.

Physical Review Letters 106, 055302 (2011).

Selected for Virtual Journal of Atomic Quantum Fluids, Vol 3, Issue 3 (2011).

Direct observation of dynamical bifurcation in a superfluid Josephson junction

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 105, 205302 (2010).

Selected for Virtual Journal of Applications of Superconductivity, Vol. 19 Issue 10 (2010).

Fiske-amplified superfluid interferometry

We report an experimental demonstration of signal amplification for a superfluid 4He interferometer by allowing the matter waves from two Josephson mass current sources to interact with the resonances within the experimental cell. We characterize the interferometer using an external phase shift and demonstrate a thirty-fold enhancement in intrinsic phase sensitivity.

Physical Review B 81, 172502 (2010).

Selected for Virtual Journal of Atomic Quantum Fluids, Vol 2, Issue 6 (2010).

Review on superfluid helium quantum interference devices

In a review article titled “Superfluid helium quantum interference devices: physics & applications”, Y. Sato and R. Packard describe recent developments in the field of superfluid Josephson phenomena and quantum interference devices.

Reports on Progress in Physics 75, 016401 (2012).

DC magnetic cloak

We report the first experimental demonstration of a “cloak” for dc magnetic fields. We utilize a material consisting of an array of artificially patterned superconducting and soft ferromagnetic elements. 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 24, 71 (2012).

Thermal cloak, concentrator, and inverter

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 cloaking, concentrating, and inverting heat current, we experimentally demonstrate the unique potential and the utility of guiding heat flux.

Physical Review Letters 108, 214303 (2012).

Selected for an Editors’ Suggestion and a Synopsis in APS Physics.

News & Views in Nature Materials.

Search & Discovery in Physics Today.

Superfluid helium interferometers

In an article titled “Superfluid helium interferometers”, Y. Sato and R. Packard describe superfluid Josephson phenomena and matter wave interferometers.

Physics Today 10, 31 (2012).

Transient heat flux shielding using thermal metamaterials

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.

Applied Physics Letters, In press (2013).