This award supports theoretical research and education on novel quantum phases in orbital and large spin systems with cold atoms. The research explores novel quantum phases and emergent symmetries with cold atoms which are not accessible in usual solid state systems and provides guidance for new experiments. The application of symmetry principles is essential for this project which not only deepens our understanding but also provides the guidance to new discoveries. A variety of methods in condensed matter physics and field theory are employed, including bosonization, the renormalization group, the large-N method, the self-consistent mean-field theory, and band structure calculations.
The first research topic is the study of novel quantum phases in high orbital bands in optical lattices. The p-orbital bosons exhibit complex-valued many-body wave functions characterized by the formation of on-site orbital angular momentum moments. The research encompasses orbital superfluidity in various lattices which exhibit collinear ordering (e.g., staggered and stripe-like), non-collinear ordering, and ''frustrated'' distributions of orbital angular momentum moments. For fermionic orbital systems, the research will focus on the honeycomb lattice, which is a p_xy-orbital counterpart of graphene. The second research topic is the study of large spin physics with cold fermions. Particular attention is paid to spin-3/2 systems which possess a generic SO(5) symmetry without fine tuning. The symmetry gives rise to important consequences such as the protected degeneracy in collective excitations, new properties of the quantum Monte-Carlo sign problem, the quintet pairing superfluidity, and the four-fermion quartetting superfluidity. Planned investigations include quantum magnetism in the spin-3/2 systems and other large spin systems as well, such as the pseudospin-1 systems and the spin-5/2 systems. The research will provide new ideas on exotic orbital superfluidity, orbital exchange physics, and emergent quantum magnetic states. It also suggests new directions for future experiments. Knowledge gained from this research deepens our understanding on strong correlation physics in both cold atom and condensed matter systems.
This research lies at the interface between condensed matter and cold atom physics and will benefit both fields. Students will receive training in the application of the symmetry principles and the research will stimulate students to develop broad interests and skills in the frontiers of strongly correlated systems. Aspects of the research, particularly the underlying theoretical techniques, form part of the subject matter of the advanced physics courses being developed by the PI at his university.
NONTECHNICAL SUMMARY: This award supports theoretical research and education that seeks to predict new states of matter composed of ultracold atoms in artificial crystals of light. Researchers have found that atoms can be trapped in modulated laser beams much like electrons are trapped in the force fields of atomic nuclei in a crystalline solid. Electrons have two internal configurations; these are related to their magnetic properties. Atoms can have many more internal configurations, leading to possible new states of matter that have no counterparts in conventional materials, but have intriguing properties and may display interesting phenomena. The research develops theories to explain the novel quantum mechanical properties of these cold atoms in crystals of light. The theories provide guidance for new experiments, deepening our understanding of quantum physics and states of matter and leading to new discoveries. This is fundamental research that lies at the interface of atomic and condensed matter physics. However, systems of cold atoms are intriguing and may hold possibilities for future technologies. Conspicuous among these is the potential to realize powerful new methods of computation based on the principles of quantum mechanics.
This research lies at the interface between condensed matter and cold atom physics and will benefit both fields. Students will receive training in the application of the symmetry principles and the research will stimulate students to develop broad interests and skills in the frontiers of strongly correlated systems. Aspects of the research, particularly the underlying theoretical techniques, form part of the subject matter of the advanced physics courses being developed by the PI at his university.
? Ultra-cold atom physics has become a new research frontier at the interface between condensed matter physics and atomic, molecular, optical physics. The research of this award is aimed at the study of novel states of matter with cold atoms in artificial lattices generated by laser beams often termed as optical lattices. Researchers have found that atoms can be trapped in modulated laser beams like electrons in solid state crystals. Compared to solid state systems, an apparent advantage of cold atom systems is that they can be controlled with unprecedented precisions. The ultra-cold atom systems not only provide ideal model systems to simulate usual condensed matter physics, but also open up a whole new opportunity for exploring novel physics which cannot easily accessible in solids. Furthermore, systems of cold atoms are intriguing and may hold possibilities for future technologies. The research of this award has given rise to a variety of important results. A novel state of matter of unconventional Bose-Einstein condensates (BEC) was predicted theoretically, which has been experimentally observed recently in optical lattices. The usual BECs are described by positive-definite distribution functions, while the unconventional BECs are described by complex-valued functions which allow much richer properties. Various strongly correlated novel quantum phases of fermions are also predicted in optical lattices, which provide important guidance for the future experiments. Unlike electrons which only have two internal configurations responsible for their magnetic properties, many alkaline earth atoms have several internal states, leading to much richer magnetic properties that have no counterparts in solids. Particularly, their magnetic states exhibit the dominant N-body correlations with N larger than two. This is similar to that at least three quarks are needed to form a baryon, such as proton or neutron. It is amazing that in spite of the huge difference of energy scales, the ultra-cold atom physics can share the same feature of the high energy quantum chromodynamics. The research of this award explicitly proposed to use alkaline earth atoms to study these exotic properties, and recently has aroused a great deal of experimental interests. This research greatly deepens our understanding on quantum magnetism and superfluidity, and benefits both condensed matter and cold atom physics. Students have received solid trainings on skills for the study of strongly correlated systems. The research results have formed part of the subject matter of the advanced physics courses taught by the PI.
