Fractional quantum Hall effect in CdTe

The fractional quantum Hall (FQH) effect is reported in a high mobility CdTe quantum well at millikelvin temperatures. Fully developed FQH states are observed at filling factor 4/3 and 5/3 and are found to be both spin-polarized ground state for which the lowest energy excitation is not a spin flip. This can be accounted for by the relatively high intrinsic Zeeman energy in this single valley two-dimensional electron gas. FQH minima are also observed in the first excited $\left(N=1\right)$ Landau level at filling factor 7/3 and 8/3 for intermediate temperatures. In contrast, the 5/2 FQH state remains absent down to $T\sim 10\text{mK}$.

Figure 1

(Color online) Hall resistance $R_{xy}$ and longitudinal resistance $R_{xx}$ versus perpendicular magnetic field for different temperatures.

Figure 2

(Color online) (a) Longitudinal resistance $R_{xx}$ at $\nu =4/3$ as a function of inverse temperature for cooldown A (stars) and for cooldown B at $\theta =0°$ (circles) and $\theta =55.6°$ (triangles). Same data for cooldown B at $\nu =5/3$ (open symbols). Simulations of the thermally activated resistance (dashed lines) (see text). Inset: corresponding total FQH gaps at $\nu =4/3$ and $\nu =5/3$ as a function of the total field $B_{total}$. Expected evolution of the gaps for different ground states (dotted lines) (see text). (b) Angular dependence of magnetotransport in the upper spin branch of the $N=0$ LL at fixed temperature $T\sim 390\text{mK}$. Increasing tilting angle $\theta$ indicated by the arrow. (c) Schematic representation of the CF fan diagram at fixed CF cyclotron energy as a function of the Zeeman energy (see text). $E_{\text{CF}}\left(N\right)$ is the energy of the $N\text{th}$ CF level. The arrows depict the spin orientation of each subband. (d) Position of the CF level crossings in the ($\left|B_{\text{CF}}^{\ast }\right|$, $B_{total}$) plane (see text). The arrows depict the spin polarization of the ground state in different region.

Figure 3

(Color online) Magnetoresistance $R_{xx}$ in the lower spin branch of the $N=1$ LL at $T=534\text{mK}$. Corresponding filling factors are indicated on top. Inset: angular dependence of the $\nu =7/3$ minimum at $T=600\text{mK}$.