Angular dependence and photon energy dependence ofcyclotron resonance in PbSe/PbEuTe quantum dotcrystals

摘要

We have observed cyclotron resonance (CR) from selfassembledPbSe quantum dots embedded in a PbEuTe matrix in very highmagnetic fields up to 150 T generated by the single turn coil techniqueand using a CO2 laser at wavelengths of 9.25 mm - 10.6 mm. Thetemperature of the sample was lowered to 15 - 20 K. The unique feature ofthe samples is that the quantum dots are densely stacked and arrangedwith a regular period to form an fcc- like crystal. For the electron-activecircular polarization, we observed sharp CR peaks from the PbSe quantumdots, whilst for the hole-active circular polarization, we observed thepeaks from the PbEuTe matrix. The CR peaks from the dots correspond tothe heavy electron valleys and the light electron valleys of PbSe for B//<111>. The heavy electron peak was found to split into three peaks,probably because of the strain around the dots. The absorption intensitywas found to depend dramatically on the wavelength of the laser. This isattributed to the interference effect of the laser beam in the regularlyspaced multilayers of the quantum dots. When we tilted the magnetic fieldfrom the normal direction to the sample plane, we found anomalouslylarge shift of the CR peak from the PbSe dots. The shift is completelydifferent from that in bulk PbSe. This indicates that although the cyclotronradius is much smaller than the dot size in the high fields, electrons in thedots still feel quantum potential of the dots.