Dresden 2006 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 54: Metal-insulator transitions
HL 54.1: Vortrag
Freitag, 31. März 2006, 11:15–11:30, BEY 154
Scanning tunneling spectroscopy of magnetic-field -induced localization in InSb — •Katsushi Hashimoto1, Focko Meier1, Jens Wiebe1, Markus Morgenstern2, and Roland Wiesendanger1 — 1Institute of Applied Physics, University of Hamburg, D-20355 Hamburg — 2Institute of Physics, RWTH Aachen University, D-52056 Aachen
Using scanning tunneling spectroscopy (STS), we study the microscopic nature of localization in three dimensional metallic n-InSb with a low carrier concentration of 1.4 × 1014 cm−3. First, we confirmed by transport measurements that extreme quantum limit (EQL) and a metal-insulator (MI) transitions caused by magnetic-field-induced localization occur at BEQL ≈ 150 mT and BMI ≈ 280 mT. The microscopic measurements using STS are performed on cleaved InSb (110) in ultra high vacuum at 0.3 K. When the B-field is set to 0 mT, dI/dV maps at a sample bias voltage (Vs) of 0 mV show two-lobe-like maxima in the local density of state (LDOS), which are merged at a negative Vs. The observed LDOS features are interpreted as quantized states confined by the potential valley, such as p-like and s-like states. They, however, abruptly vanish at BEQL. This can be correlated to enhanced electron-electron interactions with respect to the potential disorder. Furthermore, we find that the confined states are recovered above BEQL and diminish as the B-field approaches BMI, suggesting that localization due to enhanced electron-donor interactions modifies the confined states.