Many-body definition of a Fermi surface: Application to angle-resolved photoemission

In real metals with interacting conduction electrons a Fermi surface (FS) can no longer be defined as separating occupied from unoccupied one-electron states in k space, but is rather given by the location of discontinuities in the momentum distribution function n(k). Here we show that this many-body theoretical definition provides a valuable prescription for FS measurements by angle-resolved photoemission, which compared to conventional FS mapping not only extends the method to metals with extremely narrow bands, but also enhances its precision in the application to wide band systems. We demonstrate this on TiTe₂ and Cu(001) as test cases.