Conference

The quantum degenerate spinor Bose gas is a new material characterized by both magnetic and superfluid order. Like other ordered magnetic materials, the gas supports magnon excitations, which are the Nambu-Goldstone bosons associated with the spontaneous breaking of rotational symmetry. We have developed techniques to create and image magnon excitations in ferromagnetic rubidium spinor condensates. At short times after their creation, magnons are observed to propagate coherently, allowing us to measure their energy dispersion with high precision through interferometry. Using high-resolution spin-sensitive imaging, we measure the magnon spectrum to be gapped due to magnetic dipole interactions (as it often is in magnetic solids). At longer times, the magnons thermalize. We show that this thermalization allows one to measure the temperature of highly degenerate gases, and to reduce this temperature further by a new form of evaporative cooling.

It was long considered a practical impossibility to extend the methods of laser cooling and trapping to diatomic molecules. Here, unlike in atoms, photon absorption can excite internal degrees of freedom (vibration and rotation), which both interrupts the optical cycling needed for motional cooling and leads to internal-state heating. We have recently demonstrated that, nevertheless, methods like those of standard atomic laser cooling and trapping can be applied to some molecules. We have achieved sub-Doppler cooling in 1-D, radiation pressure slowing and stopping of a molecular beam, and 3-D magneto-optical trapping of SrF molecules. This promises to open a wide range of scientific applications from precision measurements, to quantum information and quantum simulation, to precise control over chemical reactions.

TBA

While the Sun has long been understood to be a source of energy, the possibility that one can use the coldness of outer space as a renewable thermodynamic resource here on the surface of the Earth has been largely ignored. By using thermal radiation one can in fact access this coldness by exploiting a transparency window in the atmosphere between 8-13 µm, which overlaps strongly with the blackbody spectrum of room temperature objects. At night, passive cooling below ambient air temperature has been demonstrated using a technique known as radiative cooling, where one uses a thermal emissive surface exposed to the sky to radiatively emit heat to outer space through the transparency window. Peak cooling demand however occurs during the daytime, and is a major driver of peak electricity demand. Air conditioning of buildings, for example, accounts for 15% of the primary energy used to generate electricity in the United States. A passive cooling strategy that cools without any electricity input during the day could therefore have a significant impact on global energy consumption. To achieve cooling one needs to be able to reach and maintain a temperature below the ambient air. Daytime radiative cooling below ambient under direct sunlight has never before been achieved because sky access during the day results in heating of the radiative cooler by the Sun.

In this talk, we show how a thermal nanophotonic approach enables one, for the first time, to achieve passive radiative cooling below ambient air temperature during peak daylight hours. We first highlight the theoretical requirements necessary for daytime radiative cooling and discuss the need for a photonic approach. We next present a nanophotonic design that has the required spectral characteristics to achieve daytime radiative cooling: it is strongly reflective over visible and near-IR wavelengths but strongly emissive between 8 and 13 µm. We then present results of the first experimental demonstration of daytime radiative cooling, where we achieve a temperature of nearly 5°C below the ambient air temperature under direct sunlight. Finally, we discuss how one can use thermal photonic approaches to passively maintain solar cells at lower temperatures, while maintaining their solar absorption, indicating how photonic radiative cooling can improve a range of energy conversion processes here on Earth.

As semiconductor devices continue to evolve to deliver more within the power-performance-bandwidth trade-off envelope, logic and memory devices are undergoing a series of fundamental transitions. When viewed individually, these transitions seem to be natural evolutionary extensions of current generation technologies. However, optimal and cost-effective manufacturing of future nano-devices incorporating these changes will require significantly different approaches. Current industry infrastructure in process, materials, metrology and design tools is not geared to handle these upcoming technology needs. Revolutionary changes are needed in how we research and develop next generation technologies, and identify or even design materials with desirable mechanical, electrical and chemical properties. High volume semiconductor manufacturing tools and processes that are geared for challenges in handling seemingly incompatible materials, 3D device and packaging architectures, non-destructive nano-metrology techniques, 3D design tools and test strategies need to be developed.

Hermetic packages are used to protect microwave and millimeter-wave monolithic integrated circuits against harsh environmental conditions, including changes in atmospheric pressure, humidity, moisture, and other natural hazards that would otherwise disrupt electrical connections or damage delicate electronics.  Microelectromechanical systems (MEMS) require hermetic packaging to prevent against contaminating particles and moisture.  Hermetic packages have a fine helium leak rate of ~1x10^-11 atm-cc/sec and are known to provide the reliability in harsh environments.  Current hermetic packages are based on metal and ceramic materials.   Ceramic and metal packages are heavier, bulkier, and more expensive than organic counterparts.  At the wafer-level packaging, high temperature wafer bonding is used to form hermetic cavities that result in tall structures.  While organic packaging technology cannot provide true hermeticity, can it have a low enough leak rate to achieve competitive reliability?  This is referred as “reliability without hermeticity” or near hermetic packaging.

In this presentation, we will review the concept of hermeticity and near-hermeticity in electronic packages.  Liquid Crystal Polymer (LCP), which has permeation close to glass, will be introduced as the next generation organic material for near-hermetic packaging.  We will discuss results of LCP material characterization.  We will then present the development of sealing techniques of LCP onto LCP and LCP onto semiconductor materials to form near hermetic cavities for housing MEMS and MMICs.  Using the newly developed sealing techniques, we will demonstrate LCP wafer-level packages, surface mount packages and multi-chip modules to 40 GHz.  Examples of wafer-level packages include the lamination of LCP onto Si to cap or package RF MEMS switches and a phase shifter with LCP-packaged MEMS.  We will also present the development of low-loss surface mount LCP packages to 40 GHz.  These surface mount packages are designed with novel feedthroughs that achieve a measured insertion loss of ~0.2 dB to 0.4dB up to 40 GHz and provide embedded filters.  We will discuss bond wire compensation schemes, package to printed circuit board transition design techniques, electrical repeatability, and thermal performance of millimeter-wave surface mount packages.  Reliability evaluation will be presented to demonstrate the robustness and reliability of LCP packages.  Examples of the environmental tests include 1000 hours of 85^oC and 85% humidity, temperature cycles, thermal shock, etc.   Finally, we demonstrate the development of compact wide bandwidth passive components, multi-chip modules, and phased array antennas in multi-layer LCP boards at Ka-band.

This talk will investigate stories and science behind x-ray free electron lasers (FELs), the world’s brightest x-ray sources. The pioneering example is SLAC National Laboratory's LCLS, with which the Photocathode Group at the University of Maryland have an ongoing collaboration. In focus will be the surfaces where the beams are born: photocathodes. Such laser-driven electron sources for FELs have advanced since Einstein’s 1921 Nobel for the photoelectric effect, but significant challenges remain due to the harsh vacuum environment of an accelerator and the demanding beam quality requirements of an x-ray FEL. Efforts underway at the University of Maryland are developing self-healing photocathodes and optical methods of probing their properties. 

This seminar is sponsored by Stanford OSA

Statistical mechanics is the framework that connects thermodynamics to the microscopic world. It hinges on the assumption of equilibration; when equilibration fails, so does our understanding. In isolated quantum systems, this breakdown is captured by the phenomenon known as many-body localization. 

Many-body localized phases violate Ohm's law and Fourier's law as they conduct neither charge nor heat; they can exhibit symmetry breaking and/or topological orders in dimensions normally forbidden by Mermin-Wagner arguments; they hold potential as strongly interacting quantum computers due to the slow decay of local coherence. 

In this talk, I will briefly introduce the basic phenomena of many-body localization and review its theoretical status. To date, none of these phenomena has been observed in an experimental system, in part because of the isolation required to avoid thermalization. I will consider several dipolar systems which we believe to be ideal platforms for the realization of MBL phases and for investigating the associated delocalization phase transition. The presence of strong interactions in these systems underlies their potential for exploring physics beyond that of single particle Anderson localization. However, the power law of the dipolar interaction immediately raises the question: can localization in real space persist in the presence of such long-range interactions? 

I will review and extend several arguments producing criteria for localization in the presence of power laws and present small-scale numerics regarding the MBL transition in several of the proposed dipolar systems. Finally, I will discuss recent work exploring the possibility of translation invariance and quantum information processing in MBL systems.

Panelists: Robin Hauser Reynolds, Vivek Wadhwa, Jocelyn Goldfein; Moderator: Brian Berg

Map & Directions

Sponsored by: IEEE SCV Women in Engineering
Co-Sponsored by: IEEE CNSV & Stanford’s IEEE WIE Student Branch

Event starts: 6pm; Panel Discussion: 6:45-8:15pm.

Cost of entry goes towards food and drinks.

The dearth of female and minority computer science engineers is a timely and relevant topic. Understanding the dynamics at work here is a big part of being able to rectify the gender, ethnicity and economic disparities.
This special program will introduce CODE, a documentary film about debugging the gender gap and bridging the digital divide. It will also address the questions:
Why does the gender gap and digital divide in tech continue to grow?
What will society gain from having a more diverse group programming the products upon which we so heavily depend?

CODE director Robin Hauser Reynolds, author Vivek Wadhwa and Angel Investor/Ex-Facebook Engineering Director Jocelyn Goldfein will engage in an interactive discussion, and we hope that you will engage them as well.

The CODE documentary film needs your help! This eye-opening documentary explores the reasons behind the gender gap in coding throughout the US. Help support its efforts by donating to its Indiegogo campaign.

NAND flash memory is the ubiquitous storage memory used in from mobile devices on the low end to high performance servers on the high end. It is a growing $20B business. In this presentation, we will examine the scaling challenges and explain how by going to 3D NAND, NAND flash gets a new lease of scaling life. We will also explore alternative memory concepts to see how they can or cannot compete with NAND. Lastly, we will discuss how NAND memory fits in a computing system and the opportunities for innovation on how to use the memory.