2017/05/12 by G. M. Minkov, V. Ya. Aleshkin, O. E. Rut +6 · 1 citation
Chemistry · Engineering · Physics and Astronomy · #Advanced Semiconductor Detectors and Materials #Amplitude #Asymmetry #Atomic physics #Band gap #Chemistry #Condensed matter physics #Degeneracy (biology) #Degenerate energy levels #Density of states #Effective mass (spring–mass system) #Energy level splitting #Laser #Physics #Quantum and electron transport phenomena #Quantum mechanics #Quantum well #Topological Materials and Phenomena #Valence (chemistry) #Valence band #cond-mat.mtrl-sci
paper · pdf · doi:10.1103/physrevb.96.035310
published as Phys. Rev. B 96, 035310 (2017) · 8 pages, 11 figures
arxiv created 2017/05/12 · openalex created_date 2017/05/26 · openalex publication_date 2017/07/26 · arxiv updated 2017/08/02 · openalex updated_date 2026/08/05
The energy spectrum of the valence band in HgTe/CdxHg_1\ensuremath-xTe quantum wells of a width (8--20) nm has been studied experimentally by magnetotransport effects and theoretically in the framework of a four-band kP method. Comparison of the Hall density with the density found from a period of the Shubnikov--de Haas (SdH) oscillations clearly shows that the degeneracy of states of the top of the valence band is equal to 2 at the hole density p<5.5\ifmmode×\else\texttimes\fi1011\phantom\rule4pt0excm^\ensuremath-2. Such degeneracy does not agree with the calculations of the spectrum performed within the framework of the four-band kP method for symmetric quantum wells. These calculations show that the top of the valence band consists of four spin-degenerate extremes located at k\ensuremath≠0 (valleys) which gives the total degeneracy K=8. It is shown that taking into account the ``mixing of states'' at the interfaces leads to the removal of the spin degeneracy that reduces the degeneracy to K=4. Accounting for any additional asymmetry, for example, due to the difference in the mixing parameters at the interfaces, the different broadening of the boundaries of the well, etc., leads to reduction of the valleys degeneracy, making K=2. It is noteworthy that for our case twofold degeneracy occurs due to degeneracy of two single-spin valleys. The hole effective mass (mh) determined from analysis of the temperature dependence of the amplitude of the SdH oscillations shows that mh is equal to (0.25\ifmmode±\else\textpm\fi0.02)m0 and weakly increases with the hole density. Such a value of mh and its dependence on the hole density are in a good agreement with the calculated effective mass.