arXiv subjects

Biswajeet Nayak

Publications and source records attributed to Biswajeet Nayak.

3 recordsLinked to original sources

arXiv2026

1D Interface-Induced Real-Space Berry Curvature Gradient Encoded in SpinValley-Coupled Nonlinear Photocurrent in Lateral Heterostructure

Symmetry breaking enables helicity-dependent optoelectronic responses in quantum materials. In two-dimensional transition-metal dichalcogenides (TMDs), circular photocurrent (CPC) is typically observed under oblique illumination via the circular photon drag effect, while realization of the intrinsic circular photogalvanic effect (CPGE) under normal incidence remains challenging. Here, we report a clear signature of CPGE in chemical vapor deposition-grown monolayer 2D lateral heterostructure (LHS). By probing the nonlocal photocurrent across the 1D hetero-interface, we observe a helicity-dependent photocurrent consistent with a spin-valley-coupled CPGE-dominated mechanism driven by interface-induced Berry-curvature asymmetry, i.e., Berry curvature dipole. Spatially and spectrally resolved measurements under selective excitation of the MoSe2, WSe2, and the interface regions exhibit distinct magnitudes and polarities of the CPG responses. These contrasting behaviors highlight the opposite spin-valley dichroism for MoSe2 and WSe2, as well as enhanced valley mixing at the 1D interface. Our findings establish LHS as a robust platform for realizing a hetero-interface-induced CPGE-like response and highlight its potential for valleytronics and optospintronics.

cond-mat.mes-hall↗

arXiv2026

Dipolar excitonic quantum wires at atomically sharp lateral interfaces

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.

cond-mat.mes-hall↗

arXiv2025

Multi Moire Networks in Engineered Lateral Hetero-Bilayers: Programmable Phononic Reconfiguration and Second Harmonic Generation

Moire engineering in two-dimensional transition metal dichalcogenides enables access to correlated quantum phenomena. Realizing such effects demands simultaneous control over twist angle and material composition to modulate phonons, excitons, and their interactions. However, most studies rely on exfoliated flakes, limiting scalability and systematic exploration. Here, we demonstrate a scalable multi-moire network by vertically stacking CVD-grown monolayer lateral heterostructures. Signatures of moire non-rigidity, including phonon frequency softening, linewidth broadening, and strain localization, are attributed to two lattice relaxation modes; rotational reconstruction and volumetric dilation. Micro-angle-resolved photoemission spectroscopy reveals that interfacial orbital interactions modulate interlayer coupling. At aligned angles, molybdenum diselenides exhibit reduced valley polarization and Davydov splitting, indicating strain-induced symmetry breaking and chiral phonon effects. Notably, SHG modulation was obderved with variation in twist angle due to lower coherence and band-offset-driven phase delay. First-principles calculations support these findings. This work provides a route to programmable, scalable multi-moire platforms for opto-straintronics, quantum sensing, and on-chip photonics.

cond-mat.mes-hall↗