Indication of charge-density-wave formation in Bi(111).

Area of Science:

• Condensed Matter Physics
• Surface Science
• Materials Science

Background:

• The Bi(111) surface exhibits unique electronic properties due to its hexagonal structure.
• Understanding the electronic behavior near the Fermi level is crucial for predicting material properties.

Purpose of the Study:

• To investigate the electronic band structure and Fermi surface of Bi(111) using photoemission spectroscopy.
• To characterize the temperature-dependent energy gap and explore its relation to charge-density-wave (CDW) formation.

Main Methods:

• Angle-resolved photoemission spectroscopy (ARPES) was employed to probe the electronic states of Bi(111).
• Temperature-dependent measurements were performed to observe changes in the electronic band structure and energy gap.
• Susceptibility calculations were utilized to analyze the Fermi surface and predict CDW formation.

Main Results:

• A small, hexagonal two-dimensional Fermi surface (FS) was identified, associated with an electron band.
• An anisotropic energy gap (Delta) near the Fermi level was observed, with temperature-dependent variations.
• A transition temperature of approximately 75 K was determined for the energy gap.
• The energy gap values at 11 K were found to be 4 meV at the hexagon's corner and 7.5 meV at its side.
• Calculations suggest the formation of an incommensurate charge-density-wave (CDW) with a wavevector q(CDW)=0.106 A(-1).

Conclusions:

• The Bi(111) surface hosts a hexagonal Fermi surface exhibiting an anisotropic energy gap.
• The observed electronic properties are consistent with the formation of an incommensurate charge-density-wave (CDW) above 75 K.
• This research provides insights into the electronic instabilities and CDW phenomena in low-dimensional materials.