The 2021 Robert Hofstadter Memorial Lectures

The Physics Department is excited to announce that the 2021 Robert Hofstadter Memorial lecture will be given by Wolfgang Ketterle, the John D. MacArthur professor of physics at MIT. He leads a research group exploring new forms of matter of ultracold atoms, in particular novel aspects of superfluidity, coherence, and correlations in many-body systems. His observation of Bose-Einstein condensation in a gas in 1995 and the first realization of an atom laser in 1997 were recognized with the Nobel Prize in Physics in 2001 (together with E.A. Cornell and C.E. Wieman). He received a diploma (equivalent to master’s degree) from the Technical University of Munich (1982), and a Ph.D. in physics from the University of Munich (1986). He did postdoctoral work at the Max-Planck Institute for Quantum Optics in Garching and at the University of Heidelberg in molecular spectroscopy and combustion diagnostics. In 1990, he came to MIT as a postdoc and joined the physics faculty in 1993. Since 2006, he is the director of the Center of Ultracold Atoms, an NSF funded research center, and Associate Director of the Research Laboratory of Electronics.

His honors include the Rabi Prize of the American Physical Society (1997), the Gustav-Hertz Prize of the German Physical Society (1997), the Fritz London Prize in Low Temperature Physics (1999), the Dannie-Heineman Prize of the Academy of Sciences, Göttingen, Germany (1999), the Benjamin Franklin Medal in Physics (2000), the Knight Commander's Cross (Badge and Star) of the Order of Merit of the Federal Republic of Germany (2002), the MIT Killian Award (2004), a Humboldt research award (2009) and memberships in several Academies of Sciences. He holds Honorary Degrees from Gustavus Adolphus College, St. Peter (2005), the University of Connecticut (2007), Ohio State University (2007), and Strathclyde University (2011), and an Honorary Professorship at Northwestern Polytechnical University, Xian, China (2014).

Prof. Ketterle’s public Hofstadter lecture on Monday, April 12, 2021 is followed by the Applied Physics/Physics colloquium on Tuesday, April 13, 2021. Please join us for these fascinating lectures (both are free and open to the public). For more information contact dmoreau [at] (dmoreau[at]stanford[dot]edu).

Public Lecture (4:30 PM on Monday, April 12, 2021)

“What happened to the kilogram?”

Webinar link:

ABSTRACT: For 130 years, a cylinder made of a platinum-iridium alloy stored near Paris was the official definition of a kilogram, the basic unit of mass. This all changed on May 20, 2019: a kilogram is now defined by a fundamental constant of nature known as the Planck constant h, which relates the energy of a photon to its frequency: h= 6.62607015 10-34 kilograms times square meters per second.

Sounds complicated? In this talk, I will provide the reasons for changing the definition of the kilogram, give simple explanations what the new kilogram is conceptually, and explain how objects with exactly known masses can be realized using advanced technology.

Afternoon Colloquium (4:30 PM on Tuesday, April 13, 2021)

“Spin dynamics of ultracold atoms in optical lattices”

Webinar link:

 ABSTRACT: Ultracold atoms offer a unique platform to study spin physics. When atoms are arranged in an optical lattice in form of a Mott insulator, the atomic motion is frozen out and the study and control of the spin degree of freedom emerges as a new frontier. Heisenberg spin models, where only neighboring spins interact, are the paradigmatic model for many interesting phenomena. Until very recently, all experimental studies with cold atoms addressed the special case of an isotropic Heisenberg model. Using lithium-7 atoms and Feshbach resonances to tune the interactions, we have created spin ½ Heisenberg models with adjustable anisotropy, including the special XX-model which can be exactly solved by mapping it to non-interacting fermions. Spin transport changes from ballistic to diffusive depending on the anisotropy. For transverse spin patterns, we have found several new dephasing mechanisms related to a superexchange induced effective magnetic field. Using rubidium atoms and two atoms per site, we have realized spin 1 models. The onsite interactions give rise to a so-called-single-ion anisotropy term proportional to (S_z)^2, which plays an important role in stabilizing magnetism for low-dimensional magnetic materials. Our studies of spin dynamics illustrate the role of ultracold atoms as a quantum simulator for materials and for elucidating fundamental aspects of many-body physics.