Dipolar excitonic quantum wires at atomically sharp lateral interfaces

The gist: The lateral MoSe2/WSe2 interface serves as an intrinsic platform for engineering one-dimensional quantum matter through atomically sharp boundaries and dynamic electrostatic control.

Emergence of Interfacial Excitons

The emergence of 1D quantum matter is demonstrated at the atomically sharp interface between monolayer semiconductors using lateral MoSe2 − WSe2 heterostructures The system hosts interfacial excitonic quasiparticles that are bound to the crystal junction. Photoluminescence spectroscopy resolves these excitons into a ladder of discrete states, establishing nanoscopic 1D confinement at length scales ≲3 nm. These excitons possess exceptional large permanent in-plane electric dipole moments exceeding e × 2 nm and exhibit micron-scale, highly anisotropic diffusion confined to the interface.

Structural and Dynamic Engineering

The lateral geometry enables dynamic, in-situ reconfiguration of the exciton’s internal structure. By introducing electrostatic doping, a collapse of the dipole moment and a 20-fold reduction in radiative lifetime are demonstrated. This structural tunability establishes lateral interfaces as a uniquely powerful platform for the ‘bottomup’ engineering of 1D quantum matter. The configuration features a global back gate (BG) and split top gates (SG1, SG2) to enable the independent regulation of carrier density and in-plane electric fields.

Spectroscopic Signatures of 1D Confinement

The interfacial exciton state is experimentally identified by a dominant new resonance at EXLI ≈ 1.53 eV. Position-resolved PL imaging demonstrates that XLI emits exclusively from the 1D junction region, extending continuously along its ∼ 20 µm length. The time-correlated single-photon counting (TCSPC) yields a radiative lifetime of τ = 14.6±0.1 ns.

Quantized Motion and Dipole Moment

The XLI lineshape resolves into a ladder of narrow, discrete peaks with linewidths Γ ≈ 1–3 meV, which is an unambiguous signature of motional quantization. The energy levels follow a linear trend, En = E0 + ħωxn, yielding a harmonic level spacing of ħωx = 7.2 ± 0.5 meV. The extracted dipole lengths yield de-h ∼ 2.2 nm for the lowest state (n = 1) and decreasing systematically to ∼ 1.6 nm for higher state (n = 5)

Tunability via Dipole Collapse

Upon introducing either electron or hole doping, the XLI state undergoes a sharp, continuous blue shift of ∆E ≈ 70 meV within a narrow voltage window 0.5 V) or hole (VBG < −2 V) doping, the XLI state undergoes a sharp, continuous blue shift of ∆E ≈ 70 meV within a narrow voltage window (∼ 1 V)> This lifetime collapse occurs in synchrony with the observed blue shift, suggesting that both observables probe a common underlying reconfiguration of the exciton’s internal structure. The proposed behavior is the direct result of a gate-controlled “dipole collapse”. This structural change inferred solely from temporal dynamics predicts the order of magnitude spectral shift, providing definitive evidence for the dipole-collapse mechanism.

Implications for Quantum Matter

The high mobilities (∼1200 cm2/Vs) suggest that interfacial excitons are protected by suppressed momentum relaxation due to reduced dimensionality. This suggests the atomically sharp channels as low-loss interconnects and high-performance transistors for future excitonic circuitry. The large permanent dipole moment and stable 1D confinement provide an ideal arena for many-body physics, offering a unique “knob” to realize strongly correlated phases, such as a Tonks-Girardeau gas of dipolar bosons. The lateral junction provides a unique platform for the active engineering of 1D excitonic devices and the exploration of novel quantum phases in reduced dimensions.

Methods Summary

Device fabrication involves stacking LHS flakes under an inert Ar atmosphere using a dry stacking procedure with PDMS droplets covered by a PC film. Measurements are conducted at 4 K in a cryogenic confocal microscopy setup that also provides electrical access to the sample. Lifetime measurements utilize Time Correlated Single Photon Counting (TCSPC) method with an excitation laser pulse average power 100nW. Finite-element method (FEM) electrostatic simulations are used to provide quantitative information of the inplane fields and charge densities at a Type-II TMDs lateral interface. Spectral analysis involves modeling the PL intensity as the sum of five Voigt profiles.

References

[1] Thierry Giamarchi. Quantum Physics in One Dimension. Oxford University Press, 2003 <ref:9pg12,[1] Thierry Giamarchi. Quantum Physics in One Dimension. Oxford University Press, 2003>

[2] M. A. Cazalilla et al. One dimensional bosons: From condensed matter systems to ultracold gases. Rev. Mod. Phys. 83, pp 1405–1466, (Dec 2011) <ref:9pg12,[2] M. A. Cazalilla et al. One dimensional bosons: From condensed matter systems to ultracold gases>

[3] Rafał Ołdziejewski et al. Excitonic TonksGirardeau and charge density wave phases in monolayer semiconductors. Phys.

1. In-situ structural engineering of quantum matter can be achieved by using lateral interfaces as a platform for dynamic tuning of wavefunctions within a single atomic monolayer. This allows for dynamic, in-situ reconfiguration of the exciton’s internal structure through electrostatic doping, enabling the bottomup engineering of 1D quantum matter.

2. AI systems can be developed to predict exciton properties based on gate voltages by using models derived from the paper's equations, such as de-h(VBG) = de-h ln(τ (VBG)/τ0) ln(τ/τ0). This system could accurately predict the blue shift of XLI center energy and lifetime collapse upon doping.

3. AI models can be trained to classify exciton states based on their spectral signatures, specifically distinguishing between a discrete ladder of narrow peaks and broad emission originating from random, isolated defect states. This would allow for the unambiguous identification of quantized center-of-mass (COM) motion in novel quantum systems.

4. AI can be used to design optimized device architectures by simulating the effects of different gate configurations on the in-plane electric field Fx. This system could predict which split-gate arrangements yield the most effective anti-aligned fields for inducing dipole collapse, as shown in Fig 4 d and e.

5. AI systems can perform automated spectral analysis to extract key physical parameters from complex photoluminescence data, such as the harmonic level spacing of 7.2 +/- 0.5 meV or the permanent dipole length de-h.

One-dimensional (1D) quantum systems are a cornerstone of many-body physics. However, their realization in solids has traditionally relied on top-down methods, which are limited by structural disorder and coarse confinement. Here, we demonstrate a fundamentally distinct route: the emergence of 1D quantum matter at the atomically sharp interface between monolayer semiconductors. Using lateral MoSe 2-WSe 2 heterostructures, we identify interfacial excitonic quasiparticles that are bound to the crystal junction. Photoluminescence spectroscopy resolves these excitons into a ladder of discrete states, establishing nanoscopic 1D confinement at length scales of 3 nm. These excitons possess exceptional large permanent in-plane electric dipole moments exceeding e x 2 nm, and exhibit micron-scale, highly anisotropic diffusion confined to the interface. Crucially, the lateral geometry enables dynamic, in-situ reconfiguration of the exciton's internal structure. By introducing electrostatic doping, we demonstrate a collapse of the dipole moment and a 20-fold reduction in radiative lifetime. This structural tunability establishes lateral interfaces as a uniquely powerful platform for the 'bottom-up' engineering of 1D quantum matter. By enabling the dynamic tuning of wavefunctions within a single atomic monolayer, this work opens a scalable route toward 1D excitonic circuits and strongly correlated 1D bosonic phases.