Dresden 2020 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 80: Quantum transport and quantum Hall effects
HL 80.8: Talk
Friday, March 20, 2020, 11:45–12:00, POT 51
Measurements of large density of states in 2D systems: case of narrow HgTe quantum wells — •Aleksandr Kuntsevich1, Grigorii Minkov2, Nikolai Mikhailov3, and Sergei Dvoretsky3 — 1P.N. Lebedev Physical Institute, Moscow, Russia — 2Ural Federal University,Ekaterinburg, Russia — 3Institute of Semiconductor Physics, Novosibirsk, Russia
For heavy carriers, mobility and cyclotron splitting are small, magneto-oscillations are damped, and it is hard to access experimentally the density of states or effective mass. Narrow HgTe quantum wells serve as a model system. The valence band in such structures contains well-conductive Dirac-like light holes at the Γ point and poorly conductive heavy hole subband located in the local valleys.
We propose and employ two methods to measure the density of states for these heavy holes. The first method uses a gate-recharging technique to measure thermodynamical entropy per particle. As the Fermi level is tuned with gate voltage from light to heavy subband, the entropy increases dramatically, and the value of this increase gives an estimate for the density of states. The second method determines the density of states for heavy holes indirectly from the gate voltage dependence of the period of the Shubnikov-de Haas oscillations for light holes. The results obtained by both methods are in the reasonable agreement with each other. Our approaches can be applied to measure large effective carrier masses in other two-dimensional gated systems.[To be published in PRB]