Spin-splitting analysis of a two-dimensional electron gas in almost strain-free ${\text{In}}_{0.89}{\text{Ga}}_{0.11}\text{Sb}/{\text{In}}_{0.88}{\text{Al}}_{0.12}\text{Sb}$ by magnetoresistance measurements

We investigated the spin-splitting in an almost strain-free ${\text{In}}_{0.89}{\text{Ga}}_{0.11}{\text{Sb/In}}_{0.88}{\text{Al}}_{0.12}\text{Sb}$ two-dimensional electron gas (2DEG) by magnetoresistance measurements at 1.5 K. A large effective gyromagnetic factor ($g$ factor) $\left|g^{\ast }\right|=33–34$ was obtained by means of the coincidence method, which assumes an effective mass $m^{\ast }=0.021m_0$ at the Fermi energy. In spite of the large $g$ factor and the high mobility $\left(\mu =9.8\times {10}^4{\text{cm}}^2/\text{V}\text{s}\right)$, a vanishing spin-splitting was also found around $B\sim 0.8\text{T}$ by analyzing the second derivative of the magnetoresistance. This effect originates from the interplay between the Rashba and Dresselhaus spin-orbit interactions, and we theoretically confirmed the fact that the Dresselhaus spin-splitting energy $\Delta E_{0D}=3.5\text{meV}$ was more than twice as large as the Rashba spin-splitting energy $\Delta E_{0R}=1.5\text{meV}$. Moreover, we demonstrated that the theoretical curves of the normalized spin splitting, including the $g$ factor and the spin-orbit interactions, were well fitted to the experimental points with the Dresselhaus spin-orbit interaction. Therefore, we concluded that the Dresselhaus spin-orbit interaction is dominant in our 2DEG in spite of its narrow band gap.

Figure 1

Schematic layer structure of our InGaSb/InAlSb 2DEG.

Figure 2

Magnetoresistance curves as a function of the inverse perpendicular magnetic field $1/B_P$ for various tilted angles. The curves are offset by $250\Omega$. The dashed curves are a guide to the eyes to indicate the Zeeman spin-splitting enhancement.

Figure 3

Second derivative of a magnetoresistance curve as a function of the inverse magnetic field $1/B$. The arrow indicates the narrowest peak corresponding to zero spin splitting.

Figure 4

Schematics of Landau levels (a) with the Rashba spin-orbit interaction and (b) with the Dresselhaus spin-orbit interaction. The effective $g$ factor is negative.

Figure 5

Calculated conduction band profile (solid curve), as well as the distribution of electron concentration (dashed curve) near the channel.

Figure 6

Magnetic field dependence of the normalized spin splitting with the experimental and the calculated results assuming (a) the Rashba term and (b) the Dresselhaus term. The closed and open circles indicate the experimental and the calculated points, respectively. The error bars of the experimental points correspond to the Landau level broadening of 0.6 meV.