Shell structure and electron-electron interaction in self-assembled InAs quantum dots

Abstract

Using far-infrared spectroscopy, we investigate the excitations of selforganized InAs quantum dots as a function of the electron number per dot, 1 ≤ n e ≤ 6, which is monitored in situ by capacitance spectroscopy. Whereas the well-known two-mode spectrum is observed when the lowest (s-) states are filled, we find a rich excitation spectrum for n e ≥ 3, which reflects the importance of electron-electron interaction in the present, strongly non-parabolic confining potential. From capacitance spectroscopy we find that the electronic shell structure in our dots gives rise to a distinct pattern in the charging energies which strongly deviates from the monotonic behavior of the Coulomb blockade found in mesoscopic or metallic structures.

Multipole modes and spin features in the Raman spectrum of nanoscopic quantum rings

“…These values are close to the ones used 21 to describe the rings studied by Lorke et al 3 The electron effective mass m*ϭ0.063 ͑we write m ϭm*m e with m e being the physical electron mass͒ and effective gyromagnetic factor g*ϭϪ0.43 have been taken from the experiments, [32][33][34] and the value of the dielectric constant has been taken to be ⑀ϭ12.4. The model is strictly two-dimensional, and as a consequence of circular symmetry, the single particle ͑s.p.͒ wave functions are eigenstates of the orbital angular momentum l z and can be written as u nl (r) Figure 1 shows the addition energies ⌬ 2 (N) at zero magnetic field.…”

Transport and Capacitance Spectroscopy of Quantum Dots

“…As di scussed i n Ref. [16], the two -dim ensional mo del i s to o p oor fo r the self -assembl ed QD s; m oreo ver, the brea ki ng of the general i zed Ko hn theo rem [33,34], observed i n the self-assembl ed QD s [35], suggests tha t the conÙnem ent p otenti al signi Ùcantl y di˜ers fro m the pa ra b oli c p otenti al . For the self-assembl ed QD s, the m odel conÙning potenti al s i n the form of the Ùnite recta ng ul ar p otenti al well [15] and the G aussian p otenti al [25] m uch b etter account f or the conducti on-ba nd o˜set at the InAs/ G aAs i nterf ace and the varyi ng com p ositi on wi thi n the InG aAs do ts [36].…”

Quantum box energies as a route to the ground state levels of self-assembled InAs pyramidal dots

“…In this particular case ͑i.e., Qϭ1), the heavy-holes ground state energies of the cubes are the same, to within 5%, as those of the pyramids, for 66 ÅϽV 1/3 Ͻ150 Å, which is the region of interest, in which the typical ͑uniformly sized and distributed͒ experimental selfassembled pyramidal dot dimensions range. [17][18][19][20][21] Nevertheless we have found that even for structures of a given shape and volume, E gs varies depending on the particular aspect ratio Q of the dot. This variation is volume dependent in the sense that the range of Q within which ⌬E gs ϭ͓E gs (Q) ϪE gs (Qϭ1)͔/E gs (Q) ͑i.e., the percentual variation of the ground state energy of a structure with a given Q, relative to that of a structure with Qϭ1) is, say, 3%, is smaller for small volumes than it is for large volumes.…”