Atomic, Biophysics, Condensed Matter, & Plasma Physics

 

Areas of Research

Atomic, Molecular, and Optical Physics Condensed Matter Theory
Biophysics Plasma Physics
Condensed Matter Experiment

ATOMIC, MOLECULAR, AND OPTICAL PHYSICS

The MIT AMO group is anchored by the NSF Center for Ultracold Atoms (CUA), a joint effort between MIT and Harvard.  Their research focuses on creating and understanding quantum systems with strong interactions and correlations. One theme is many-body physics, in which many atoms interact and form new quantum phases of matter. A second theme involves few particles (atoms and photons) with entanglement and correlations.

This research is made possible by newly developed atomic physics techniques and technology including high-resolution lasers, atom and ion traps, and atom interferometry. Ultracold samples of atoms, prepared by laser and evaporative cooling are crucial for this work.

A watershed example of ultracold phenomena is Bose Einstein Condensation, for which Prof. Ketterle received the Nobel Prize in 2001. With Prof. Pritchard, he is now loading these condensates into lattices made of standing waves of light to study phenomena such as the Mott-insulator transition and quantum magnetism. 

A condensate can also be used to refrigerate clouds of Fermi atoms (which lack collisions with each other and are therefore difficult to cool by themselves) in order to realize superfluidity and, in optical lattices, to study the fermionic Mott insulator and magnetic ordering. Another project is the formation of ultracold NaLi molecules from a sodium/lithium mixture. Prof. Zwierlein is conducting experiments on fermionic superfluids and strongly interacting Fermi liquids, where bare fermions are dressed into quasiparticles called Fermi polarons. He is also preparing experiments on fermionic pairing of potassium and lithium atoms which may form Cooper pairs of dissimilar fermions.

Prof. Chuang studies quantum information with cold atomic systems, based on microfabricated chips for cooling, moving, and controlling small numbers of individual ions at the quantum level. His cryogenic ion traps enable new schemes for controlling polar molecular ions and studying their quantum interactions. Prof. Vuletic works on quantum control of systems with few degrees of freedom. This includes generation of single and twin photons, the use of photons to transfer quantum information between atomic systems, and spin squeezing which can be used to increase the accuracy of atomic clocks beyond the usual shot noise limit. He is also studying collisions between cold ions and neutral atoms.

The Atomic Physics group is vitally involved in educational activities, Prof. Kleppner with the Teaching Opportunities for Students program (TOPS) and Prof. Pritchard with his education group - Research in Learning Assessment and Tutoring (http://RELATE.mit.edu).

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BIOPHYSICS

The field of biophysics has experienced tremendous growth and excitement in recent years. The Physics of Living Systems Group within the Physics Department at MIT includes over 60 scientists spread across eight research groups. Our goal is to combine a rigorous training in physics together with an interdisciplinary approach to modern problems in biophysics. Graduate students in the Department benefit from an interactive and supportive intellectual community, including the opportunity to earn a Graduate Certificate in Biophysics.

Biophysics research within the Department spans many scales, from the structural organization of polymers to the evolutionary and ecological dynamics of populations. Professor George Benedek is one of the pioneers in the biophysics of “soft” materials, and currently works on various forms of protein condensations and phase transitions. Professor Ibrahim Cissé uses physical techniques to visualize weak and transient biological interactions, to study emergent phenomena in live cells with single molecule sensitivity. Professor Jeff Gore uses microbial populations to experimentally test fundamental ideas in theoretical ecology and evolutionary dynamics.

On the theoretical front, Professor Jeremy England and his group focus on structure, function, and evolution in the sub-cellular biophysical realm. Professor Mehran Kardar is a statistical physicist with interests in pattern formation, protein knots, and the immune response. Additionally, three theorists have joint appointments in the Department. Professor Leonid Mirny is a computational systems biologist with major efforts devoted to characterizing the spatial organization of the genome and the evolutionary dynamics in cancer. Professor Sebastian Seung is a computational neuroscientist trying to elucidate the “connectome” of the brain. Professor Arup Chakraborty uses statistical mechanical methods to complement biological experiments and clinical data to understand how the adaptive immune system works.

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CONDENSED MATTER EXPERIMENT

As in other fields of physics, progress in condensed matter may result from new technology. For example, the capability developed by the electronics industry of making semiconductor and metal structures on the nanometer length scale has made possible the subfield that makes up much of what is now called nanoscience. Our Department enjoys a leadership role in this area, with Prof. Ashoori and Prof. Kastner working on semiconductor nanostructures, including single electron transistors and capacitors, and Prof. Jarillo-Herrero and Prof. Dresselhaus who are leaders in the field of carbon nanotubes and graphene. The MIT Condensed Matter Physics group has enjoyed a tradition of close collaboration and mutual stimulation between theorists and experimenters. An example of such synergism is the prediction by Prof. P. Lee and the first observation by Prof. Kastner’s group of a low energy resonance in quantum dots due to spin fluctuations of the confined electron.

A second major focus of the condensed matter physics group is on strongly correlated electronic materials related to high TC superconductors. On the experimental side, Prof. Y. Lee is performing neutron and X-ray scattering, as well as thermal and transport measurements on novel superconductors and frustrated quantum magnets. He also leads an effort focused on growing single crystals of these correlated electron systems and also synthesizing new compositions of matter. Prof. Gedik studies the dynamics of elementary excitations in strongly correlated systems using ultra-fast pump probe spectroscopy. He also employs short pulses of electrons generated by femtosecond laser pulses to perform diffraction and study the non-equilibrium lattice dynamics in response to electronic excitations. Recent advances in scanning tunneling microscopy (STM) have made possible the measurement of local electronic density with atomic resolution down to millikelvin temperatures, allowing the study of vortices and impurities in the high TC superconductors.

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CONDENSED MATTER THEORY

The condensed matter theory group at MIT covers a broad range of activities that can roughly be divided into four major themes:

  • One is the study of strongly correlated materials, where the strong interaction between electrons in the solid state gives rise to novel phenomena. Examples are the fractional quantum Hall effect and high temperature superconductivity.
  • A second direction is the study of how electronic behavior is changed when the electrons are confined to nanometer-size structures, either in man-made quantum dots or in carbon nanotubes or nanowires. The phase coherence of the electron waves leads to novel behavior, and the understanding of phase coherence is crucial for the development of quantum computation and quantum information science.
  • A third theme is nano-photonics: manipulation of light on length-scales substantially shorter than the wavelength of light, on very short time-scales, and at ultra-low energy levels.
  • Finally, tools and concepts of statistical physics are employed to study the structure, function, and evolution of biological molecules, cells, and networks, as well as other complex forms of soft condensed matter. In all of these areas, the methodology includes analytic tools based on field theory methods, the development of computer algorithm, and the use of high performance computation.

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PLASMA PHYSICS

The plasma research effort at MIT is concerned with a wide variety of problems, ranging from astrophysical plasmas to laboratory and fusion-grade plasmas, as well as with using plasmas for environmental remediation. This work combines theory and experiment and involves faculty members from physics and other departments. The program has the goals of understanding the physics of plasmas and charged-particle beams and of designing plasma containment devices, with the ultimate aim of achieving the conditions in which a plasma can ignite by fusion reactions. Research is carried out not only on-site, but also at other major national and international laboratories.

Most of the volume of the universe is in the electrodynamic plasma state. Moreover, the dynamics of the universe on a grand scale is described as a gravitational plasma. The theory of galaxies as gravitational plasmas is well-developed and its results, for example, spiral arm structures, are relatively well-correlated with the experimental observations. While many aspects of laboratory plasmas are understood and correlate with experiments in relatively simple magnetic geometries, the physics of high-temperature plasmas on a microscopic scale continues to be an area of intensive investigation.

The dynamics of laboratory plasmas, charged-particle beams, and space and astrophysical plasmas are often strongly influenced by the excitation of collective modes with similar characteristics and common theoretical descriptions. The interaction of collective modes, both with each other and with charged particles, results in a variety of highly nonlinear phenomena of great importance for fusion, astrophysical and nonneutral plasmas, as well as for accelerators and coherent radiation sources.

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