Imaging Viscous Flow of the Dirac Fluid in Graphene

Imaging Viscous Flow of the Dirac Fluid in Graphene

July 23, 2020

It sounds like pure sorcery: using diamonds to observe invisible power swirling and flowing through carefully crafted channels. But these diamonds are a reality. [Harvard Physics Associate Mark J. H. Ku, and postdoc Tony Zhou, together with other members of Prof. Amir Yacoby's group, JQI Fellow Ronald Walsworth, and colleagues from several other institutions], have developed a way to use diamonds to see the elusive details of electrical currents.

The new technique gives researchers a map of the intricate movement of electricity in the microscopic world. The...

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Fig. 1a: chematic of TDBG with a twist angle θ.

Tunable Spin-Polarized Correlated States in Twisted Double Bilayer Graphene

July 9, 2020

Reducing the energy bandwidth of electrons in a lattice below the long-range Coulomb interaction energy promotes correlation effects. Moiré superlattices—which are created by stacking van der Waals heterostructures with a controlled twist angle—enable the engineering of electron band structure. Exotic quantum phases can emerge in an engineered moiré flat band. The recent discovery of correlated insulator states, superconductivity and the quantum anomalous Hall effect in the flat band of magic-angle twisted bilayer graphene has sparked the exploration of correlated electron states in...

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Forming a Single Molecule in an Optical Tweezer (artist's representation)

Longer Lived Molecules

July 1, 2020

Individual molecules placed in precisely defined quantum states could provide the building blocks for molecular arrays for quantum computing applications. But first, researchers need to develop techniques for creating these molecules. Now Jessie Zhang at Harvard University and colleagues demonstrate such a technique for forming a long-lived single NaCs molecule in a specific, reversible quantum state...

Continue reading "Longer Lived Molecules" by...

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Shut Down STEM poster

Towards a More Inclusive Physics Community

June 14, 2020

On June 10, 2020, the Department held a special department-wide meeting of the Equity & Inclusion Committee for a discussion focusing on how we can increase the number of African American physicists. Introductory comments by Department Chair, Prof. Subir Sachdev, are below.

Dear all,

I would like to make some personal remarks to mark the deaths of George Floyd, Ahmaud Arbery, Breonna Taylor, and many others, and recent national events.

I grew up in India and have spent my adult life in America. India and America have much in...

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Vafa book cover

"Puzzles to Unravel the Universe" -- New Book by Prof. Cumrun Vafa

June 12, 2020

Beneath all of the complex and formidable mathematical structures that formulate physical laws rest simple but deep nuggets of truth. It is these simple truths, and not the complicated technical details, that scientists strive for when uncovering the laws of nature. Fortunately, these core ideas can often be illustrated with simple mathematical puzzles. These puzzles are so simplified that one can tackle them and appreciate their meaning without using any complicated math. 

A new book by Prof. Cumrun Vafa, Puzzles to Unravel the Universe, aims to take the reader...

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Lase cooling setup

Laser-cooled YbOH molecules could aid the hunt for new physics

May 4, 2020

Physicists at Harvard University and Arizona State University in the US have succeeded in laser-cooling YbOH molecules – a crucial first step towards using these molecules to make precision measurements of the electron’s electric dipole moment (eEDM). Their work was augmented by a related effort, carried out by researchers at the California Institute of Technology (Caltech) and Temple University, to enhance the brightness of a beam of cold YbOH. The results appear in separate ...

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Figure 1: a new refrigerator for molecules

Collisional Cooling of Ultracold Molecules

April 8, 2020

A diatomic molecule consists of two atoms, held together by a chemical bond. But these molecules are more than just a pair of atoms: if one atom is different from the other, the molecules become polar. This polarity empowers the diatomic molecules to strongly interact with each other, even at long distance. These molecules can also vibrate or rotate--something that single atoms cannot do--giving us extra-knobs to control their quantum behavior. These special features of the molecules make them important and powerful candidates for quantum computers and quantum simulators as well as a...

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