Fig. 3
From: Evidence for a topological excitonic insulator in InAs/GaSb bilayers
Excitonic insulator gap and topological edge states. a Sketch of the measurement setup. b Arrhenius plot of the conductance minimum for different back-gate bias voltages. The data can be fit by σ xx ∝ exp(−Δ/2k b T) to obtain Δ. Here the σ xx is normalized by its value at 2.5 K. Dashed lines are guides to the eye. Black circles are for V b = 0 V, red squares are for V b = −1.5 V, green down-triangles are for V b = −3 V, blue up-triangles are for V b = −4.5 V, and yellow stars are for V b = −6 V. c Measured gap energy Δ as a function of back-gate bias voltage. d Diagram for capacitance measurement. In addition to the dc V f and V b, a small low frequency ac voltage was applied to the front-gate, and the capacitance between the front-gate and the quantum wells was measured. e Gap energy as a function of temperature for V b = 0 V. At the charge-neutral point, the gap energies were extracted from c q. The dotted-dashed line is from the calculation. The error bars come from the uncertainties in c q and the temperature. f Nonlocal measurement performed in a mesoscopic H-bar for V b = 0 V at 0 T and 30 mK. The electrical current is passed through contacts 3 and 4, and the voltage is measured between contacts 1 and 2. The dashed line indicates the expected resistance value calculated from the Landauer–Büttiker formula. The edge current path is shown in the inset as red and green arrows
