Dephasing time of two-dimensional holes in GaAs open quantum dots: Magnetotransport measurements

We report magnetotransport measurements of two-dimensional holes in open quantum dots, patterned as either a single dot or an array of dots, on a GaAs quantum well. For temperatures $T$ below $500\mathrm{mK}$, we observe signatures of coherent transport, namely, conductance fluctuations and weak antilocalization. From these effects, the hole dephasing time ${\tau }_{\varphi }$ together with an upper limit for the spin-orbit scattering time are extracted using the random matrix theory. The calculated ${\tau }_{\varphi }$ shows a $T$ dependence close to $T^{-2}$, and its absolute value is found to be approximately one order of magnitude smaller than that reported for electrons.

Figure 1

Upper panel: Magnetoconductance of D1 for $p=2.3\times {10}^{15}{\mathrm{m}}^{-2}$ at $T=80$ (bold trace), 95, 135, 200, 300, and $500\mathrm{mK}$. For clarity, traces are shifted upward by $0.5e^2∕h$. A magnetoconductance trace measured in a second cooldown is also shown and is shifted downward by $1.5e^2∕h$. Inset: Scanning electron microscope picture of D1. Lower panel: Magnetoconductance of A1 for $p=2.3\times {10}^{15}{\mathrm{m}}^{-2}$ at $80\mathrm{mK}$.

Figure 2

(Color online) $g\left(B\right)-g(B=0)$ as a function of $B$ at indicated temperatures for (a) A1 and (b) A2 at $p=2.3\times {10}^{15}{\mathrm{m}}^{-2}$ as well as (c) A1 and (d) A2 at $p=1.7\times {10}^{15}{\mathrm{m}}^{-2}$. Solid lines show the fits of the WAL peak using the RMT. The mean conductance $⟨g⟩$ at $B=0$ is given for each case.

Figure 3

Dephasing time ${\tau }_{\varphi }$ of holes as a function of $T$. (a) ${\tau }_{\varphi }$ extracted from the WAL correction to the conductivity in samples A1 and A2. (b) ${\tau }_{\varphi }$ calculated from the variance of the MCFs in samples D1 and D2. Open and solid symbols correspond to asymmetric and symmetric confining potentials, respectively. The dotted lines indicate various $T$ dependencies. Error bars are determined from uncertainties in the number of modes in the quantum point contacts and in the dots areas.

Figure 4

Magnified view of the MCFs of (a) D1 and (b) D2 at $p=2.3\times {10}^{15}{\mathrm{m}}^{-2}$ and $T=80\mathrm{mK}$ after background subtraction (see text). The mean conductance $⟨g⟩$ is calculated in the range $-0.2<B<0.2\mathrm{T}$. (c) Variance of the MCFs as a function of $T$ for D1 and D2.