Monolayer transition metal dichalcogenides having giant valley-polarized Rydberg excitons revealed by magneto-photocurrent spectroscopy
A transition metal dichalcogenides device includes a substrate, at least one layer of boron nitride, a tungsten diselenide monolayer positioned such that the at least one layer of boron nitride at least partially encapsulates the tungsten diselenide monolayer, and a plurality of electrodes. Each of the plurality of electrodes includes gold and few-layer graphene, and the at least one layer of boron nitride includes hexagonal few-layer boron nitride. The tungsten diselenide monolayer is configured to reveal excitons when at least one of a K valley and a K′ valley of the tungsten diselenide monolayer is exposed to excitation photon energy and an external magnetic field. The excitons are giant valley-polarized Rydberg excitons in excited states ranging from 2 s to 11 s when the external magnetic field is in the range of about −17 T to about 17 T.
1. A transition metal dichalcogenides device comprising:
a substrate;
at least one layer of boron nitride;
a tungsten diselenide monolayer positioned such that the at least one layer of boron nitride at least partially encapsulates the tungsten diselenide monolayer; and
a plurality of electrodes comprising:
a source electrode positioned on the substrate;
a drain electrode positioned on the substrate; and
a top gate electrode positioned on a top layer of the at least one layer of boron nitride.
2. The device of claim 1 , wherein each of the source electrode, drain electrode, and top gate electrode comprise gold and few-layer graphene.
3. The device of claim 1 , wherein the at least one layer of boron nitride comprises hexagonal few-layer boron nitride.
4. The device of claim 1 , wherein the substrate comprises at least one of a silicon dioxide layer and a silicon layer.
5. The device of claim 1 , wherein the tungsten diselenide monolayer is configured to reveal excitons when at least one of a K valley and a K′ valley of the tungsten diselenide monolayer is exposed to excitation photon energy and an external magnetic field.
6. The device of claim 5 , wherein the excitons are giant valley-polarized Rydberg excitons in excited states ranging from 2 s to 11 s when the external magnetic field is in the range of about −17 T to about 17 T.
7. A system for revealing excitons in a transition metal dichalcogenides comprising:
a broadband light source configured to emit excitation photon energy;
a tunable filter configured to filter the excitation photon energy to a predetermined wavelength bandwidth;
a linear polarizer configured to linearly polarize the filtered excitation photon energy; and
a quarter waveplate configured to convert the linearly polarized excitation photon energy into circularly polarized excitation photon energy to excite the transition metal dichalcogenides.
8. The system of claim 7 , wherein an external magnetic field is applied to the transition metal dichalcogenides when it is exposed to the focused circularly polarized excitation photon energy.
9. The system of claim 7 , further comprising a half waveplate positioned between the linear polarizer and the quarter waveplate.
10. The system of claim 9 , further comprising a mechanical chopper positioned between the half waveplate and the quarter waveplate.
11. The system of claim 7 , wherein the broadband light source comprises a supercontinuum laser.
12. The system of claim 7 , further comprising a focusing element configured to focus the circularly polarized excitation photon energy to excite the transition metal dichalcogenides.
13. The system of claim 7 , wherein the predetermined wavelength bandwidth is about 1 nm.
14. The system of claim 7 , wherein the transition metal dichalcogenides comprises:
a substrate;
at least one layer of boron nitride;
a tungsten diselenide monolayer positioned such that the at least one layer of boron nitride at least partially encapsulates the tungsten diselenide monolayer; and
a plurality of electrodes.
15. The system of claim 14 , wherein the tungsten diselenide monolayer is configured to reveal excitons when at least one of a K valley and a K′ valley of the tungsten diselenide monolayer is exposed to the focused circularly polarized excitation photon energy and the external magnetic field.
16. The system of claim 15 , wherein the excitons are giant valley-polarized Rydberg excitons in excited states ranging from 2 s to 11 s when the external magnetic field is in the range of about −17 T to about 17 T.
17. A method of revealing excitons in a transition metal dichalcogenides comprising:
providing the transition metal dichalcogenides, the transition metal dichalcogenides comprising:
a substrate;
at least one layer of boron nitride;
a tungsten diselenide monolayer positioned such that the at least one layer of boron nitride at least partially encapsulates the tungsten diselenide monolayer; and
a plurality of electrodes;
exposing the transition metal dichalcogenides to an external magnetic field;
emitting excitation photon energy from a broadband light source;
filtering, via a tunable filter, the excitation photon energy to a predetermined wavelength bandwidth;
linearly polarizing, via a linear polarizer, the filtered excitation photon energy;
converting, via a quarter waveplate, the linearly polarized excitation photon energy to circularly polarized excitation photon energy; and
focusing, via a focusing element, the circularly polarized excitation photon energy onto the tungsten diselenide monolayer of the transition metal dichalcogenides.
18. The method of claim 17 , wherein the tungsten diselenide monolayer is configured to reveal excitons when at least one of a K valley and a K′ valley of the tungsten diselenide monolayer is exposed to the focused circularly polarized excitation photon energy and the external magnetic field.
19. The method of claim 18 , wherein the excitons are giant valley-polarized Rydberg excitons in excited states ranging from 2 s to 11 s when the external magnetic field is in the range of about −17 T to about 17 T.