Abstract

Discovery of new topological materials is of great interest due to their unique transport properties and surface states. Most topological materials verified to date involve materials with specific crystalline symmetries, that ensure degeneracies in the electronic band structure, or materials containing heavy elements with strong spin-orbit coupling. Lithium is the lightest metal on the periodic table at standard temperature/pressure, and ostensibly a simple metal assuming a close-packed structure under ambient conditions. However, with increasing pressure it has been found to surprisingly undergo structural phase transitions to low symmetry structures that are predicted to be semi-metallic and even insulating. We predict that along with these interesting structural phase transitions, there is also an evolution in the topological properties of lithium and the semi-metallic high pressure phases are topologically nontrivial. Using ab initio techniques, we can characterize and understand how these topological features arise in a light elemental solid under pressure and are well-isolated from the trivial electronic bands. Our results indicate that lithium has previously unexplored topological properties in its pressure phase diagram.