Far-infrared Resonance Spectroscopy Research Articles

Quantum wires and quantum dots on indium antimonide

The authors report on the study of quantum wires and dots near the surface of InSb that contain quasi-one-dimensional and zero-dimensional, i.e. discrete, electron systems. Both types of samples are derived from metal-oxide-semiconductor devices and make it possible to tune the electron number by a gate voltage. The laterally confining potential leads to the formation of one-dimensional sub-bands and to discrete levels respectively. Both are examined by far-infrared resonance spectroscopy. In order to attain a sufficiently high absorptance they fabricated the wires and dots by holographic lithography in arrays on macroscopic areas. Resonance energies of about 10 meV due to the lateral quantisation are found to be comparatively large because of the low conduction band mass of InSb. In particular, the influence of the narrow-gap band structure of InSb and of the electron-electron interaction on the quantised levels is discussed.

Far-infrared resonance spectroscopy and the effective intermolecular potential.

The Kramers equation is solved numerically for circular diffusion in an arbitrary periodic potential V(\ensuremath{\theta}), where \ensuremath{\theta} is the angular coordinate. In the limit \ensuremath{\beta}\ensuremath{\rightarrow}0, where \ensuremath{\beta} becomes proportional to the rate of escape from the potential wells, the far-infrared power absorption coefficient shows many different peaks due to resonance in highly nonlinear systems as described by Bogoliubov and Mitropolsky for ordinary, nonlinear, differential equations. The far-infrared resonance spectrum (FIRRS) is sensitive to the details of V. In structured (associated or hydrogen-bonded) molecular liquids such as water or acetonitrile, or in liquid crystals, the FIRRS peaks can be resolved experimentally. These peaks provide, in principle, detailed information on the effective intermolecular potential in systems of interest such as nematogens. The FIRRS spectrum is sensitive to an applied, uniaxial, external, static, electric or magnetic field.