Physics phenomena6/19/2023 ![]() ![]() Importantly, skyrmions are topological objects, or those whose properties do not change even when they are subjected to large deformations. In a skyrmion, the spins form knot-like whirls that are distributed across the surface of a material. In the magnets on your refrigerator, the spins all point in the same direction. The spin can be thought of as an elementary magnet, in which the electrons in an atom are like little needles orienting in a certain way. Key to the research is an exotic particle called a skyrmion that involves a property of electrons called spin (another, more familiar property of electrons is their charge). And that's when all the really interesting things in our field happen," Paul continues. Getting electrons to be still, however, allows them "to really talk to each other. And it takes a lot of fine-tuning to get them to stand still," says Paul. "That was the theoretically challenging part because it's not a very straightforward thing to ask of an electron. Specifically, the team predicts that a structure made of two layers of a 2D magnet topped by a layer of a 2D semiconductor material will generate a phenomenon called a flat band, in which the electrons in the semiconductor stand still. What might happen if the two fields-2D magnets and moiré materials-are combined? That is the focus of the current work. ![]() Separately, other scientists have advanced the field of 2D magnets. MIT Physics Professor Pablo Jarillo-Herrero pioneered the field with moiré graphene, which is composed of two sheets of atomically thin layers of graphene placed on top of each other and rotated at a slight angle. Those sandwich structures, in turn, are called moiré materials. "The whole world of two-dimensional materials is very interesting because you can stack them and twist them, and sort of play Legos with them to get all sorts of cool sandwich structures with unusual properties," says Paul, first author of the paper. The current work was guided by recent advances in 2D materials, or those consisting of only one or a few layers of atoms. His colleagues are Nisarga Paul, a physics graduate student, and Yang Zhang, a postdoctoral associate who is now a professor at the University of Tennessee. Fu is also affiliated with the Materials Research Laboratory. "This work started out as a theoretical speculation, and ended better than we could have hoped," says Liang Fu, a professor in MIT's Department of Physics and leader of the work. The team includes the conditions necessary to achieve that ultimate goal in a paper published in the February 24 issue of Science Advances. numerical approaches to electronic structure methods.The work is theoretical, but the researchers are excited about collaborating with experimentalists to realize the predicted phenomena.coherent control in both time and energy domains.The list of proposed contributions is broad and interdisciplinary, including themes such as: Given the above background, our goal in the present Research Topic is to discuss the current status of the fields of coherent control, coherence spectroscopy, and more generally coherent phenomena in chemical physics, and to point to future directions. ![]() This led to what we refer to as coherent spectroscopy – a field that aims to understand molecular motions and uses to that end the coherence property of light, rather than temperature or pressure. Only more recently it was realized that the most important application of coherent control is to understand chemical dynamics. It did not take long for the analogy of coherent control of chemical dynamics to the application of phase in optics and physics to be understood. Before this conceptual shift, the standard, incoherent tools such as temperature, pressure, and chemical catalysts were used. The introduction of coherent control has empowered studies of chemical physics since the mid-eighties, when this approach has emerged, striving to go beyond understanding to controlling molecular motions, using the coherence property of laser fields. ![]()
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