Rowland Institute at Harvard


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Rowland Institute at Harvard

Harvard University


Superfluid Helium Quantum Interference Devices

By placing two (and more) “weak links” in a loop of superfluid helium as in a dc-SQUID, a unique matter wave interferometer can be realized. We have constructed and used such interference devices for rotation sensing through Sagnac effect, measurement of quantum phase gradient associated with superfluid flow, detection of quantized vortex line motion, and construction of an absolute gauge for quantum mechanical phase shifts. We are working on further developing our matter wave interferometers to investigate novel interactions that give rise to quantum phase shifts in a neutral matter system. By taking advantage of the macroscopic coherent nature of our superfluid system, we are developing more sensitive and more practical superfluid gyroscopes to contribute to fields such as seismology, geodesy, inertial navigation, and general relativity. With an asymmetric interference grating, we are also using superfluid as a test bed for studying the formation of topological defects and second order phase transitions.

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Superfluid Helium Weak Links

While most quantum mechanical effects only appear in matter on the atomic or subatomic scale, superfluids, like superconductors and Bose-Einstein condensates, can exhibit the effects of quantum mechanics acting on the bulk properties of matter on a large scale. When two such quantum systems are weakly coupled together, various fascinating phenomena emerge. In condensed matter systems, superconductors coupled through thin insulators and micro-bridges were the first of this kind to be extensively studied. In our research, we couple two reservoirs of superfluid helium through nanoscale apertures and study their properties governed by quantum mechanics at the macroscopic scale.

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Metamaterials & Devices

Various manipulation methods of energy flow have been explored recently with artificial material engineering. Unusual phenomena can result from the characteristics of individual elements, and more importantly, from their engineered internal structures. As conventional media owe their properties to the average response from an ensemble of atoms and molecules, in metamaterials, each structural unit plays the role of an atom. In our group, we take advantage of the great flexibility arising from this emergent nature and construct artificial media and devices with novel properties tailored to external fields and energy flow of interest.

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Mass/Particle Sensing

Direct measurement of bond, interaction strengths and rupture force have been studied using AFMs, nanowire FETs, and optofluidic devices. We develop new experimental methods and engage in novel device instrumentation for sensitive mass/particle sensing for a wide range of research topics.


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