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Séamus Davis's Group detect Cooper pair density waves

The prediction was that “Cooper pairs” of electrons in a superconductor could exist in two possible states. They could form a “superfluid” where all the particles are in the same quantum state and all move as a single entity, carrying current with zero resistance – what we usually call a superconductor. Or the Cooper pairs could periodically vary in density across space, a so-called “Cooper pair density wave.” For decades, this novel state has been elusive, possibly because no instrument capable of observing it existed.

Now a research team led by J.C. Séamus Davis, the James Gilbert White Distinguished Professor in the Physical Sciences, and Andrew P. Mackenzie, director of the Max-Planck Institute CPMS in Dresden, Germany, has developed a new way to use a scanning tunneling microscope (STM) to image Cooper pairs directly.

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Hamidian and Edkins studied a cuprate incorporating bismuth, strontium and calcium (Bi2Sr2CaCu2O8) using an incredibly sensitive STM that scans a surface with sub-nanometer resolution, on a sample that is refrigerated to within a few thousandths of a degree above absolute zero.

At these temperatures Cooper pairs can hop across short distances from one superconductor to another, a phenomenon known as Josephson tunneling. To observe Cooper pairs, the researchers briefly lowered the tip of the probe to touch the surface and pick up a flake of the cuprate material. Cooper pairs could then tunnel between the superconductor surface and the superconducting tip. The instrument became, Davis said, “the world’s first scanning Josephson tunneling microscope.”

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 Graphic depiction of a periodic variation in the density of Cooper pairs (pairs of blue arrows pointing up and down) across the surface of a cuprate superconductor.

Science Goes to the Movies hosts Mukund Vengalattore

In episode #204 of Science Goes to the Movies, series co-hosts Dr. Heather Berlin and Faith Salie are joined by Mukund Vengalattore, atomic physicist and Assistant Professor of Physics at Cornell University, to talk about quantum physics in the British sci-fi show, Doctor Who.

Starting off the discussion is a look at Vengalattore’s well-publicized quantum theory research on a phenomenon very similar to what is seen on Dr. Who from the beings known as “weeping angels.” Vengalattore explains the various tenets of quantum theory, including that a system shouldn’t change while it is being looked at, or measured, which his work aims to elucidate in order to develop a better understanding of how to control a quantum system. Making atoms cold, letting them loose in a contained environment, and carefully watching their movement is explained as a process that leads to the atoms being frozen in place, just like the “weeping angels.”

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Mukung Vengalattore - Science goes to the Movies

Séamus Davis awarded St. Patrick’s Day Science Medal

Science Foundation Ireland presented its prestigious St. Patrick’s Day Science Medal March 16 to Séamus Davis, Cornell’s James Gilbert White Distinguished Professor in the Physical Sciences. The presentation was made by Charles Flanagan, Ireland’s minister for foreign affairs and trade, as part of St. Patricks’ Day celebrations in Washington, D.C.

This is a wonderful honor, not only for me but for all the scientists at institutions worldwide that form our collaborative research network,” said Davis at the award ceremony. “This award highlights exciting opportunities now emerging from networking the scientific research communities in Ireland and here in the United States. Both countries benefit from this positive relationship, with cross-Atlantic collaboration now playing a vital role in the success of many of the most advanced scientific projects.

“This science medal is also a testament to the world-leading quality of scientific education in Ireland, and to the deep commitment to promote and enhance Ireland’s educational standards today. I am extremely grateful to Science Foundation Ireland for this medal, and I express my gratitude to my family, especially all those at home in Ireland, and to all my colleagues, past and present.”

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More on the SFI award

LASSP faculty play role in founding Cornell Neurotech

The Cornell Neurotech collaboration was born from humble beginnings when several faculty members began meeting informally in the Physical Sciences Building to discuss their work and share research opportunities regarding neuroscience and technology.

The group had been encouraged by Paul McEuen, co-director of the Kavli Institute at Cornell—which not only provided nominal funding for the monthly meetings, but since 2011 had also been pushing a much larger national research initiative to substantially invest in studies of the brain.

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Dr Mohammad Hamidian wins the Lee Osheroff Richardson Science Prize

Early in his PhD at Cornell University (Ithaca, NY, USA), Dr Hamidian took on the challenge of developing an ultra-low vibration milliKelvin stage based upon an Oxford Instruments custom-designed version of the Kelvinox®400 dilution refrigerator. He designed and constructed a novel STM scanning head for that environment, devised a complete change of protocol for STM control and operation at milliKelvin temperatures, and enhanced the control of the dilution refrigerator itself to suppress vibration to many orders of magnitude below a commercially achievable scale. This system was the first successful milliKelvin spectroscopic imaging STM in the world and remains among only a handful in existence.

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Dr. Mohammad Hamidian's Website

 

Dr Hamidian - 2016 Lee Osheroff Richardson Science Prize Winner

Gruner and Sethna part group that developes the first self-assembled superconductor

Sol Gruner and James Sethna are part of a collaboration that has created the first self-assembled, three-dimensional gyroidal superconductor. The gyroid is a complex cubic structure based on a surface that divides space into two separate volumes that are interpenetrating and contain various spirals. Pores and the superconducting material have structural dimensions of only around 10 nanometers, which could lead to entirely novel property profiles of superconductors.

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self assembled superconductor