Orbital degree of freedom in artificial electron lattices on metal surface

TL;DR

This paper demonstrates through calculations and experimental data that artificial p-orbital fermionic lattices have been realized on metal surfaces, enabling new studies of orbital degrees of freedom in solid state systems.

Contribution

It reveals that high energy states in artificial electron lattices correspond to p-orbitals, establishing a new platform for orbital physics in condensed matter.

Findings

Artificial p-orbital fermionic lattices have been realized.

High energy states correspond to p-orbitals in the lattice.

This enables controlled studies of orbital degrees of freedom.

Abstract

Orbital degree of freedom plays a fundamental role in condensed matter physics. Recently, a new kind of artificial electron lattice has been realized in experiments by confining the metal surface electrons with adsorbed molecular lattice. A most recent example is the Lieb lattice realized by CO adsorption on Cu(111) surface [M. R. Slot, et al., Nat. Phys. 13, 672(2017)]. The Lieb lattice is of special interest due to its flat band physics. Here, by first-principles calculations, muffin-tin potential model and tight binding model, we demonstrate that, the high energy states observed in the experiment actually correspond to the artificial $p$-orbitals of the electron lattice. Our numerical results, together with the experimental observation, show that artificial $p$-orbital fermionic lattice has already been realized in solid state system. This opens a new avenue to investigate the orbital degree of freedom in a controllable way.