Surface-enhanced charge-density-wave instability in underdoped Bi2201

TL;DR

This paper reveals a surface-enhanced charge-density-wave instability in underdoped Bi2201, showing a temperature-dependent surface phenomenon linked to Fermi surface nesting, contrasting with bulk stability.

Contribution

It uncovers a previously unrecognized surface-bulk dichotomy in charge-density-wave behavior in cuprates, emphasizing the surface's role in electronic phase studies.

Findings

Surface-sensitive probes detect temperature-dependent Fermi surface changes.

Bulk probes show temperature-independent structural modulation.

Surface phenomena suggest a strong Fermi surface nesting-driven instability.

Abstract

Neutron and x-ray scattering experiments have provided mounting evidence for spin and charge ordering phenomena in underdoped cuprates. These range from early work on stripe correlations in Nd-LSCO to the latest discovery of charge-density-waves in YBCO. Both phenomena are characterized by a pronounced dependence on doping, temperature, and an externally applied magnetic field. Here we show that these electron-lattice instabilities exhibit also a previously unrecognized bulk-surface dichotomy. Surface-sensitive electronic and structural probes uncover a temperature-dependent evolution of the CuO2 plane band dispersion and apparent Fermi pockets in underdoped Bi2201, which is directly associated with an hitherto-undetected strong temperature dependence of the incommensurate superstructure periodicity below 130K. In stark contrast, the structural modulation revealed by bulk-sensitive probes is temperature independent. These findings point to a surface-enhanced incipient charge-density-wave instability, driven by Fermi surface nesting. This discovery is of critical importance in the interpretation of single-particle spectroscopy data and establishes the surface of cuprates and other complex oxides as a rich playground for the study of electronically soft phases.