Superfluid-Quasicrystal in a Bose-Einstein condensate Scan QR Code to Junpeng Hou, Haiping Hu and Kuei Sun access Supervisor: Chuanwei Zhang our paper. Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080, USA Phys. Rev. Lett. 120, 060407

Abstract Another distinct state of matter Experimental Setup The numerical simulations reveal many interesting phases in our happens at very low temperature is system, including superfluid-quasicrystals, supersolids with varying There are 4 fundamental states of matters, namely, solids, liquids, superfluid. Atoms are too small to be patterns and normal superfluids. gases and plasmas. From daily experiences, we know that a given Superfluidity is the characteristic controlled through any Analytic results from a “guess” matter cannot be a solid and a liquid simultaneously. However, in the property of a fluid with zero mechanical process. Instead, we zoo of quantum materials, an extraordinary phase of matter called While an exact analytic solution is way too hard, we could apply viscosity which therefore flows use laser beams to trap, cool certain approximation and make a reasonable guess about how the supersolid was recently created in Bose-Einstein condensates, which without loss of kinetic energy. and manipulate the atoms. are the coldest matters in the universe. A supersolid, inheriting the solutions look like. frictionless nature of a superfluid, also has spatial periodicity like a Superfluid was first realized in liquid helium and superfluidity was Similarly, our solid. That is, it is a fluid and a solid at the same time. In this work, also experimentally observed in Bose-Einstein condensates. proposed we further enlarge the family of quantum matters by proposing a Spatial orders in solids experimental new state of matter called superfluid-quasicrystal. We show it is Most common spatial order in solids is captured by translational scheme for possible to engineer such a novel quantum state in a Bose-Einstein symmetry. realizing condensate. Similar to a supersolid, a superfluid-quasicrystal has the Examples of translational symmetry. superfluid- properties of a superfluid. But unlike a supersolid, this novel state of quasicrystals matter forms quasicrystal, instead of crystal, patterns by itself. Our also involves work provides a platform for preparing and investigating new exotic many lasers shooting on the quantum matters, which are inaccessible in classical physics. With a trial solution by guess, we could analytically obtain for atoms. different phases and their transitions (from one phase to another). Introduction* Translation symmetry is very common The obtained diagram is called phase diagram, which describes the in solids and Methods and Results Classical states of matters phases of the system with given parameters. those solids We model the system to achieve a total Hamiltonian, which contains We are most familiar with three different forms of matters, namely, The results from both methods are consistent with each other, with all the crucial information we need to under superfluid-quasicrystals. solids, liquids and gases. Examples in daily life are ice, water and confirming the existence of superfluid-quasicrystals, an entirely new translationa Our expectations from such a setup: steam. state of matter. l symmetry are called Conclusion crystals. 1) We have proposed a scheme for realizing superfluid-quasicrystal using a Bose–Einstein condensate under proper laser control. Another classes of solids are quasicrystals. They have rotational 2) We model the system and use two approaches to study the symmetry but no translational symmetry. ground state properties. 3) We show there is a rich phase diagram containing superfluid- Rotational symmetries are also quasicrystals, supersolids, plane-wave phases, and their phase frequently seen in nature. But we need to show that the superfluid-quasicrystal could be the transitions. lowest-energy state, namely, the ground state of such a quantum- 4) Our proposed experimental setup lays out a platform for future mechanical system. theoretical and experimental investigations of such exotic novel Such a distinct form in which matter can exist stably is referred to as Numerical simulations quantum matter. state/phase of matter in physics. As we are dealing with a set of coupled nonlinear differential News Coverage Solids are characterized by structural rigidity and resistance to equations, it is hard to analytically obtain the ground state. We use Our proposal for this new state of matter has been reported by changes of shape or volume. The atoms in a solid are tightly Quasicrystals are thought to be forbidden in classical solids until numerical recipe to search for the solutions with given system many major scientific/public presses across the world. A partial list bounded to each other, forming certain spatial orders. the first discovery in 1984. parameters. goes following: Liquids are nearly incompressible but can be deformed easily. Gases can be considered as compressible fluids. Supersolid: a solid and a (super)fluid A long-hold belief is that different fundamental states of matters are The fourth fundamental incompatible. Specially, we cannot have something being ice and phase of matter: plasma, water at the same time. which can be understood as Even in quantum physics, the existence of supersolid was under a conductive gas. It happens debates for decades. But recently, researchers from MIT had created in things we saw everyday: such an exotic matter in a Bose-Einstein condensate. lightning, fluorescent lights A supersolid is a spatially and neon lights. ordered material with Matters in lower temperature superfluid properties. It When the temperature is so low that quantum effects are important, can flow on any surface there remain more to be explored. without frictions like a A Bose–Einstein condensate is a superfluid and it also has state of matter of a dilute gas of crystal patterns like bosons cooled to temperatures solids. very close to absolute zero. Since supersolid= superfluidity + crystal order, how about Acknowledgements Absolute zero is the lowest limit superfluidity + quasicrystal order? Is this beautiful state of This work was supported by Air Force Office of Scientific Research of the thermodynamic matter possible? (FA9550-16-1-0387), National Science Foundation (PHY-1505496), temperature scale, at which all A superfluid-quasicrystal inherits unique and Army Research Office (W911NF-17-1-0128). atoms are “frozen”. We cannot properties from both superfluids and *Pictures credits go to the following websites: futurism, YouTube, reach absolute zero. quasicrystals. It is frictionless like a Sci-News, Wikipedia, phys.org, etc. The coldest Bose–Einstein condensate ever made on this planet is superfluid and would form some special Contact Information about a few hundreds pK, i.e., 1 × 10−10 above the absolute zero. It’s orders with only rotational symmetry (no Office: 1.115 PHA (Phys Annex) not only the coldest matter on Earth but also in the entire universe. translational symmetry) like a quasicrystal. Email: [email protected]