Electronic structure and Fermi surface of Sn/Cu(100)-(3 root 2x root 2)R45 degrees

The surface phase Sn/Cu(100)-(3 root 2x root 2)R45 degrees exhibits a temperature induced phase transition to a (root 2x root 2)R45 degrees phase above 360 K. We report an angle-resolved photoemission study of the two-dimensional Fermi surface of the low-temperature phase. The Fermi surface is formed by folding of a quasi-two-dimensional surface band and presents three contours. It is characterized by gaps appearing in optimally nested regions of one of the contours, whereas other sections remain ungapped. We address the origin of the folding and of the surface phase transition, which is attributed to the formation of a surface charge density wave.