Nanoscale Trapping of Interlayer Excitons in a 2D Semiconductor Heterostructure

Abstract

For quantum technologies based on single excitons and spins, the deterministic placement and control of a single exciton is a longstanding goal. MoSe 2 -WSe 2 heterostructures host spatially indirect interlayer excitons (IXs) that exhibit highly tunable energies and unique spin-valley physics, making them promising candidates for quantum information processing. Previous IX trapping approaches involving moireś uperlattices and nanopillars do not meet the quantum technology requirements of deterministic placement and energy tunability. Here, we use a nanopatterned graphene gate to create a sharply varying electric field in close proximity to a MoSe 2 -WSe 2 heterostructure. The dipole interaction between the IX and the electric field creates an ∼20 nm trap. The trapped IXs show the predicted electric-field-dependent energy, saturation at low excitation power, and increased lifetime, all signatures of strong spatial confinement. The demonstrated architecture is a crucial step toward the deterministic trapping of single IXs, which has broad applications to scalable quantum technologies.

Localized interlayer excitons in MoSe2–WSe2 heterostructures without a moiré potential

“…Figure 2a shows the electric field dependence of the PL while keeping the sample charge neutral 16 . In the DC region, we observe a Stark shift of 0.6 eV/(V/nm) that matches with the known dipole moment of the IX 16 , 17 . By adding the hBN bilayer between the TMD layers, we increase the separation between the electron and hole and consequently the IX permanent dipole moment will increase by a factor of two.…”

Self-Trapped Interlayer Excitons in van der Waals Heterostructures

“…5,29−35 Strain has also been proposed as an effective way to trap the IX, in which the band structures of TMDC heterostructures are modified by strain, resulting in the static potential well. 16,36−38 The spatially varying electric fields enable the localization of the IX due to its permanent dipole moment, 10,39,40 where the deterministic placement and control of a single trapped IX have been achieved. 39 Alternatively, a free exciton could be trapped by local deformation of the lattice stemming from the strong coupling between excitons and phonons.…”

Trapping Interlayer Excitons in van der Waals Heterostructures by Potential Arrays

“…trap sizes that are comparable to those created by strains, defects, and moiré potentials. [19,20,41,42] Five potential landscapes of trap arrays with radii of 100 nm, 20 nm, 11 nm, 5 nm and 2.5 nm are constructed (Figure 2a). For ease of comparison, all of these primary trap potentials have the same total area.…”

“…[14,15] The transport of IXs can be modulated by their localizationdelocalization transitions across lattice potentials. [16,17] Moreover, the strong repulsive dipole-dipole interactions among IXs can be engineered by confining them in potential traps created by strains, disorders or moiré potentials, [18][19][20] which may provide rich opportunities * xuedan.ma@anl.gov for the study of quantum optical nonlinearities and creation of quantum photon sources. [21][22][23] While great strides have been made in trapping IXs in TMDs using strains and moiré potentials, [18,20,24,25] the influence of the potential trap nature, such as the trap geometries and densities, on the related photodynamics of the IXs including their trapping and localization remain largely unexplored.…”