Bose Einstein Condensates (BEC) carry all particles in the same quantum state, an effect known for nearly a century. In this project we propose to create and study novel micro and nano hybrid BECs.
Research Interests
Based on a theory proposed by the Indian physicist SathyendraNath Bose in 1924 Einstein proposed that it is possible to have all particles in a system, however large, occupy the same quantum state. We now know that it is only those particles which have an integer quantum spin, termed bosons, that can form such a macroscopic quantum state. Hence the term Bose Einstein Condensation. This phenomenon first observed in liquid helium below a temperature of 2.2 K endows the system with such exotic properties as superfluidity or frictionless flow. While extreme low temperatures are required to observe a BEC in helium analogous phenomena have recently been discovered to occur closer to room temperature with magnons, packets of magnetic energy,which are also ‘bosons’ in magnetic materials. The phenomenon of superconductivity, a related effect, has been observed at room temperature just a few months ago. Thus, the study of BEC phenomena together with similar effects observed in optically cooled atomic gases, holds promise for many future quantum technologies.
BECs are actively pursued at the University in several laboratories in physics and in chemistry. Cold atom BECs have been established in the Sackett lab in physics and most recently by Peter Schauss. Superfluid helium droplets have been investigated by the Lehmann group in Chemistry for several decades where the non-dissipative nature of the superfluid mechanical vacuum enables ultra-high resolution spectroscopy. Such experiments are performed on microdroplets released in a freely expanding cold jet of helium gas. Shivaram who started his career working with superfluid helium has focused thus far at the University on studies of superconductivity.
The project proposed here brings together intellectual wealth accumulated separately over decades in Chemistry and in Physics. We seek to establish two new paradigms in the study of BECs:
(a) Develop engineered and localized micro and nano BEC droplet arrays and
(b) Develop hybrid BECs composed of superfluid helium mixed with atomic/molecular dopants.
The first step in the project will be the experimental realization of BEC arrays. This is based on a novel scheme conceived by Shivaram based on the recognition that helium does not wet Cesium. Helium being a Van der Waals system wets all substances except for Cesium where it is known to ball up and form droplets. By micro and nano-patterning of high purity Cesium films grown in-situ we will localize helium BEC droplets in those regions where we have ablated or etched away the Cesium. For droplets that are sufficiently close to one another by controlling the temperature we should be able to establish quantum communication between the droplets. The meniscus between the droplets is temperature dependent and the thickness of the intermediate region can thus be manipulated with temperature thus controlling the mass flow of quantum particles between the droplets. Our second step will be to dose the droplets with cold atoms carefully chosen from the periodic table. We will study properties of the droplets as well as that of the dopants by measuring their spectroscopic and their flow characteristics.
Desired outcomes
A low temperature cryostat capable of providing sub kelvin temperatures will be assembled and outfitted with viewports. Schemes to grow high purity Cesium films in an ultra-high vacuum environment and their subsequent micro and nanoscale patterning will be developed. An atomic beam source will be developed and integrated into the cryostat and used to introduce select atomic species onto the localized helium droplets. The optics and the electronics necessary for the spectroscopic and flow measurements on the droplets will be assembled and such measurements will be carried out. The above tasks will be performed over a period of two years – the requested time frame of the project. We expect the results obtained in this two-year period will enable us to write several proposals to the National Science Foundation on fundamental studies of micro and nano scale superfluid BECs, and to the Defense agencies such as the ARO,ONR and AFOSR which have interests in new quantum sensors, cryogenic energy storage and super fluid gyroscopes. We also expect our work will result in peer-reviewed publications and potential patent disclosures.
Student engagement
There are numerous opportunities for students at all levels to be engaged in this exciting project. Fabrication of high purity Cesium thin films in a cryogenic environment and subsequent patterning is a good undergraduate project. Undergraduate students will learn cryogenic and thin film deposition techniques as well as get introduced to the microfabrication facilities available on grounds in engineering. Similarly, the construction of the cold atomic beam source is a stand-alone undergraduate project. Performing spectroscopic and flow measurements are rightful graduate level projects and constitute appropriate thesis topics for doctoral work in physics and chemistry. Thus, with the funds requested we plan on involving at least two undergraduate and two graduate students. These funds will be supplemented as appropriate by other resources for the project to succeed. There are funds available through a current grant from NSF in physics (Shivaram). All three participants listed have undergraduate students who are eager to get started in this project.
Further, all three applicants in the current project are also participants in a related MRI proposal that is currently pending at the NSF in which funding close to $1 million has been requested. This funding from the VPR’s office is a seed for cross-disciplinary studies where new paradigms in the study of BECs are introduced. It holds the potential for revolutionary scientific discoveries.