Nana Shumiya

Abstract Charge-density-wave implies a periodic modulation of the charge density. Typically observed in metallic systems, charge-density-wave arise from Fermi surface instabilities, resulting in the total or partial gapping of the Fermi surface. Here, we present experimental evidence for a charge-density-wave state emerging in a band insulator which has no Fermi surface. The bulk and surface of our material platform, \({\rm{\alpha }}\)-Bi4Br4, is gapped over the entire Brillouin zone.

The lifetime of superconducting qubits is limited by dielectric loss, and a major source of dielectric loss is the native oxide present at the surface of the superconducting metal. Specifically, tantalum-based superconducting qubits have been demonstrated with record lifetimes, but a major source of loss is the presence of two-level systems in the surface tantalum oxide.

Popular Summary Superconducting qubits are one of the most successful quantum platforms, and they have been integrated into some of the largest processors to date. Building large-scale systems that are robust to computational errors will require improvements in the underlying hardware to extend the quantum coherence of individual qubits.