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LASSP -  Laboratory of Atomic and Solid State Physics

Cornell Laboratory for Atomic and Solid State Physics

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Jeevak Parpia's research group look for new phase transitions

When Cornell physicists Robert Richardson, David Lee and Douglas Osheroff received the 1996 Nobel Prize for their discovery of the superfluid state of liquid helium, it was only the beginning. Now a new team of Cornell researchers, building on that work, have found new complexities in the phenomenon, with implications for the study of superconductivity and theoretical models of the origin of the universe.

“We wanted to see new phase transitions,” said Jeevak Parpia, professor of physics. As it turned out, he saw a more “efficient” transition compared to any observed before in helium.

The results are published July 3 in the journal Nature Communications. Parpia and his research group collaborated with a group led by John Saunders, professor of physics, at Royal Holloway, University of London.

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Séamus Davis recognized in The Irish Times

Séamus Davis was recognized in The Irish Times as an Irish quantum physicist bringing superconductor resech a sep closer to the 'hoy grail' of quantum physics.

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Séamus Davis, Eun-Ah Kim, Kyle Shen, Darrell Schlom, and Craig Fennie win $1M Keck Foundation Grant

A cross-campus collaboration led by Cornell engineering professor Darrell Schlom has been awarded $1 million from the W.M. Keck Foundation to transition its groundbreaking research from bold theory, based on extensive calculation, to creating a specific topological superconducting material that could pave the way to quantum computing.

“We have state-of-the-art capabilities to make artificial materials and interrogate their properties that are relevant to quantum computing, and this is a particularly exciting system for materials discovery because of its complexity and potential payoff,” said Schlom, the Herbert Fisk Johnson Professor of Industrial Chemistry in the Department of Materials Science and Engineering.

Other team members are J.C. Seamus Davis, the James Gilbert White Distinguished Professor in the Physical Sciences; Craig Fennie, associate professor of applied and engineering physics; Eun-Ah Kim, associate professor of physics; and Kyle Shen, associate professor of physics.

The team’s project is titled “A Materials-by-Design Approach to an Odd-Parity Topological Superconductor,” and its goal is to discover a material that will lay the foundation for a stable and scalable quantum computing technology.

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Erich Mueller and Shovan Dutta challenge generally accepted notion on solitons

Solitary waves – known as solitons – appear in many forms. Perhaps the most recognizable is the tsunami, which forms following a disruption on the ocean floor and can travel, unabated, at high speeds for hundreds of miles.

By definition, a soliton retains its shape while propagating at a constant velocity. But what happens when two, or more, solitons interact? The general consensus from past studies is that solitons are essentially unchanged by such an interaction and pass through one another, but physics professor Erich Mueller and graduate student Shovan Dutta have challenged that notion in a report just published in Physical Review Letters.

Their paper, “Collective Modes of a Soliton Train in a Fermi Superfluid,” was published June 29. Both men work in Cornell’s Laboratory of Atomic and Solid State Physics.

The team found something drastically different for solitons interacting in a superfluid, which forms when a gas of atoms is cooled to near absolute zero. Not only do the solitons affect one another, but they can even collide and destroy each other.

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Parpia's researchers change the fundamental frequency of an object’s motion by simply applying voltage

A professor, a postdoctoral researcher and a graduate student hop onto a trampoline.

No, it’s not the opening line of a joke. It’s a setup for the explanation of new Cornell-led research involving the wonder material graphene. A group led by Roberto De Alba, graduate student in physics, and Jeevak Parpia, professor and department chair of physics, has published a paper in Nature Nanotechnology regarding yet another application for the versatile, super-strong, super-light material.

Their paper, “Tunable phonon-cavity coupling in graphene membranes,” was published June 13 and describes the ability to use the graphene’s tension as a sort of mediator between vibrational modes, allowing for direct energy transfer from one frequency to another. De Alba was lead author.

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Eun-Ah Kim and Yi Zhang's Research Highlighted in Viewpoint

Viewpoint: Neural Networks Identify Topological Phases

A new machine-learning algorithm based on a neural network can tell a topological phase of matter from a conventional one.

A detailed characterization of phases of matter is at the forefront of research in condensed-matter and statistical physics. Although physicists have made incredible progress in the characterization of a wide variety of phases, the identification of novel topological phases remains challenging. Now, Yi Zhang and Eun-Ah Kim from Cornell University, New York [1], have taken a big-data approach to tackling this problem. In their work, thousands of microscopic “images” or “snapshots” of a phase, created using a special topography procedure, are fed into a machine-learning algorithm that is trained to decide whether these images come from a topological or a conventional phase of matter—exactly as modern computer vision algorithms are designed to tell cats from dogs in a picture.

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Figure 1: Zhang and Kim’s machine-learning algorithm for identifying a topological phase of matter involves a procedure called quantum loop topography (QLT). The procedure builds a multidimensional image from several adjacent, triangular loops located at the pixels of snapshots of the phase’s electronic density (only one such snapshot is shown here). The QLT image is then fed into a neural network that is trained to determine whether the image corresponds to a topological phase or not.