Potassium Atoms in 2D Triangular Superlattice

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

Advanced technologies are fueled by advances in our understanding of materials. Given that a material is composed of a specific selection of atomic elements in a specific crystalline form, we seek to understand what are the macroscopic properties of the material in terms of electrical and heat conduction, magnetization, and so on. This understanding is often obtained from numerical simulation. However, a new paradigm is emerging for the exploration of materials science: quantum simulation. In this new approach, properties of a material are understood by creating a physical simulacrum of the material, i.e. a highly controlled system that obeys the same microscopic rules as those governing the real material, but a system in which physical properties can be readily tuned and measured. In this project, the research team will simulate the properties of materials using a gas of potassium atoms, cooled to extremely low temperatures, and trapped within a regular structure produced at the intersection of several laser beams (an optical lattice). The motion of the ultracold gas of atoms in this optical lattice mimics the motion of electrons in a crystal. By taking high-resolution images of the atomic gas, the team will gain insight that can guide the design of new materials. Students engaged in the project will receive valuable training in the expanding field of quantum information science. The specific scientific focus of this project is the role of geometric frustration and flat bands in artificial ultracold atomic and also solid state materials. Ultracold potassium atoms will be placed within optical lattices of several geometries, including the honeycomb lattice and the kagome lattice. Both these lattices support a band structure that includes flat bands, i.e. a macroscopic degeneracy of states in which the energy does not vary with quasi-momentum. The team will conduct experiments using the fermionic isotope of potassium, 40-K, in order to probe and verify the flatness of these bands, explore the implication of flat bands on the thermodynamics of itinerant fermions, and study the possibility of metallic, ferromagnetic, charge-density-wave modulated, and superconducting states of fermions in flat-band optical lattices. The findings of this work will advance our knowledge of complex electronic phases that arise in flat-band and heavy-fermion materials. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.