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TT: Tiefe Temperaturen
TT 6: Postersitzung I: Mesoskopie(1-21), amorphe Metalle und Defektsysteme(22-29), Kryotechnik, Kernmagnetismus(30-37), festes N2(38), Quantenflüssigkeiten und -kristalle(39-48), dünne supraleitende Filme(49-68), schwere Fermionen und Kondosysteme(69-92), Fullerene(93-94)
TT 6.11: Poster
Dienstag, 18. März 1997, 09:30–13:00, Z1
Local Voltage Measurements in Multiprobe Conductors — •T. Gramespacher and M. Buttiker — Département de Physique Théorique, Université de Genève
We investigate multiterminal resistances of a mesoscopic conductor measured with the help of a scanning tunneling microscope. Based on the scattering approach for multiterminal conductors and based on the Hamiltonian formulation of the scattering matrix, we derive an expression for the tunneling conductance between the tip and an arbitrary contact of the sample [1]. Our conductance formula manifestly satisfies the Onsager-Casimir reciprocity relations. In the special case of an atomically sharp tip, the tunneling current is proportional to a local partial density of states [2] rather than the total local density of states. If the relevant tunneling current density extends over a region wider than the Fermi wavelength, the tunneling probability is strongly suppressed due to interference effects. This is in contrast to what would be expected from a simplified Bardeen-like formula. The tunneling measurement is compared with a voltage measurement that is obtained by using the tip as a small capacitor [3].
[1] T. Gramespacher and M. Buttiker (unpublished).
[2] V. Gasparian, T. Christen and M. Buttiker, Phys. Rev. A (1996) (in press); M. Buttiker, Phys. Rev. B 40, 3409 (1989).
[3] T. Christen and M. Buttiker, Phys. Rev. Lett. 77, 143 (1996).