Research ArticleCONDENSED MATTER PHYSICS

Electrically controllable router of interlayer excitons

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Science Advances  07 Oct 2020:
Vol. 6, no. 41, eaba1830
DOI: 10.1126/sciadv.aba1830
  • Fig. 1 Control 2D potential energy of interlayer excitons by electrical field.

    (A) PL of WSe2 bilayer. The emission centering at ~736 and ~784 nm are ascribed to the intralayer excitons and interlayer excitons transition, respectively. PL spectra of interlayer exciton for gate voltage of 0 and 10 V, showing that the peak position redshifts by ~24 nm. Sample temperature is 10 K. a.u., arbitrary units. (B) Contour plot of the interlayer exciton emission intensity as a function of the applied gate voltage and wavelength. The excitation power is 30 μW operated at 532 nm. (C) Schematic structural diagram of one excitonic transistor. (D) Schematic of exciton energy offset for exciton dynamic regimes of trap, free diffusion, and spreading when applying negative (top), zero (middle), and positive (bottom) gate voltages, respectively. (E to G) Real-space emission intensity map for exciton trap, diffusion, and spreading, corresponding to gate voltage VG = −9, 0, and 11 V, respectively. The white dashed lines indicate the bottom electrode edges. Scale bars, 2 μm. (H) Emission intensity profiles across the electrode extracted from the real-space emission intensity maps. The excitation spot was focused on the center of the electrode. The excitation power is ~200 nW operated at 532 nm.

  • Fig. 2 Exciton transistor operations.

    Real-space emission intensity map for exciton ON and OFF operation, corresponding to voltage applied to electrode 2 [E2 (G)] VG = 9 V (A), −9 V (B), respectively. The voltage applied to electrode 1 [E1 (S)] and electrode 3 [E3 (D)] is 4 and 0 V, respectively. The white dashed lines indicate the bottom electrode edges. Scale bars, 2 μm. (C) Emission intensity profiles along the solid black arrows in (A) and (B). The excitation power is ~600 nW operated at 532 nm. Both VG = 0 and 9 V can be seen as ON state, which is in stark difference with VG = −9 V (OFF state).

  • Fig. 3 Unidirectional movement for excitonic transistor operation.

    (A) Optical image of the device. The black areas are the bottom electrodes. (B) Real-space emission intensity map when one transistor is in ON state. The VS = 0 V and VD1 = −1 V create a potential energy offset, and the perturbation in gate voltage ΔVG1 = 20 V. To improve the contrast of the image, the image shows the normalized PL intensity difference between ON and OFF state when VG1,ON = 10 V and VG1,OFF = −10 V. No voltages were applied on transistors 2 and 3. (C) Real-space emission intensity map when switching on the second transistor. VS = 0 V, VD2 = −1 V, VG2,ON = 10 V, and VG2,OFF = −10 V. Voltages applied on transistor 1 are the same as those in (B). No voltages were applied on transistor 3. The white dashed lines indicate the bottom electrode edges. The excitation spot was focused on the center of the triangle electrode. The solid red arrows are a guide to the eye. The excitation power is ~100 μW operated at 730 nm. Scale bars, 5 μm.

  • Fig. 4 Point-to-point movement for excitonic router operation.

    The exciton signal routing can be achieved by directly applying electric gate voltage on ports 1, 2, and 3. All gate voltages are set to zero. (A) Exciton propagation from port 1 to port 2; V1 = 0 V, V3 = 3 V, V2,ON = −3 V, and V2,OFF = 3 V. (B) Exciton propagation from port 2 to port 3; V1 = 8 V, V2 = 0 V, V3,ON = −1 V, and V3,OFF = 10 V. (C) Exciton propagation from port 3 to port 1; V2 = 4 V, V3 = 0 V, V1,ON = −0.5 V, and V1,OFF = 6 V. (D) Excitons propagation from port 3 to both port 1 and port 2; V3 = 0 V, V1,ON = 0 V, V1,OFF = 8 V, V2,ON = 0 V, and V2,OFF = 8 V. To improve the contrast of the images, the images show the normalized PL intensity difference between ON and OFF state. The solid white arrows parallel to the excitons propagation direction are drawn as a guide to the eye. The red circles show the laser excitation spot. The excitation power is ~200 μW operated at 730 nm. Scale bars, 5 μm.

Supplementary Materials

  • Supplementary Materials

    Electrically controllable router of interlayer excitons

    Yuanda Liu, Kévin Dini, Qinghai Tan, Timothy Liew, Kostya S. Novoselov, Weibo Gao

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