Monolayer transition metal dichalcogenides having giant valley-polarized Rydberg excitons revealed by magneto-photocurrent spectroscopy

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 to excitation photon energy to a predetermined wavelength bandwidth;
• a linear polarizer configured to linearly polarize the filtered excitation photon energy;
• a quarter waveplate configured to convert the linearly polarized excitation photon energy into circularly polarized excitation photon energy;
• and
• a focusing element configured to focus the circularly polarized excitation photon energy to excite the transition metal dichalcogenides positioned on a piezo stage microscope;
• wherein an external magnetic field is applied to the transition metal dichalcogenides when it is exposed to the focused circularly polarized excitation photon energy.

A method of revealing excitons in a transition metal dichalcogenides comprising:

• providing the transition metal dichalcogenides, the transition metal dichalcogenides comprising:
• a substrate;
• a bottom layer of boron nitride;
• a tungsten diselenide monolayer positioned on the bottom layer of boron nitride;
• a top layer of boron nitride positioned on the tungsten diselenide monolayer such that the bottom layer of boron nitride and the top layer of boron nitride at least partially encapsulate the tungsten diselenide monolayer;
• a source electrode positioned on the substrate;
• a drain electrode positioned on the substrate;
• and
• a top gate electrode positioned on the top layer of boron nitride;
• 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 50× objective, the circularly polarized excitation photon energy to a spot size of about 2 μm onto the tungsten diselenide monolayer of the transition metal dichalcogenides.