A phenomenological approach of joint density of states for the determination of band structure in the case of a semi-metal studied by FT-STS

The authors show that an accurate determination of the band structure can be achieved by using Fourier transform scanning tunnelling microscopy (FT-STM) techniques in the case of a semi-metallic ErSi2 layer grown on a Si(111) substrate. This material provides an ideally confined 2D electron and hole gas that is reflected in a complex standing wave pattern at 77 K. The quasi-particles exist over a wide energy range from -800 to +300 meV without mixing with silicon bulk excitations. The Fourier transform of dI/dV maps have been successfully interpreted using the concept of the joint density of states (JDOS), which will be properly introduced. We present here an intuitive interpretation of the quasiparticle interference process based on a geometric construction which also allows us to clearly demonstrate that hole-hole and hole-electron quantum interferences dominate over electron-electron quantum interference.