arXiv subjects

Rwik Dutta

Publications and source records attributed to Rwik Dutta.

4 recordsLinked to original sources

arXiv2026

Topology and compact molecular orbitals in twisted bilayer WSe$_2$

Recent observations of superconductivity in twisted bilayer WSe$_2$ (tWSe$_2$) have motivated theoretical proposals for unconventional pairing mechanisms. A central question is whether band topology plays an essential role in the system's correlation physics. In this letter, we develop a first-principles-based description of the top moir\'e valence bands in tWSe$_2$. Using density functional theory (DFT) calculations, we identify the bands in the relevant range of twist angles to be topologically non-trivial, with the top valence bands carrying Chern numbers $C=(+1,+1)$ for the $K$ valley. In order to treat the strong correlation physics, we construct compact molecular orbitals directly from the DFT wave functions through a partial Wannierization procedure and with the guidance of spinful $C_{3z}$ symmetry representations. This yields a localized $f$ orbital together with a complementary topological $c$ orbital, allowing us to extract hopping and hybridization amplitudes from first principles. The resulting parameters provide an ab initio benchmark for the effective Hamiltonian. Our work establishes a foundation for understanding superconductivity in moir\'e TMDs and highlights tWSe$_2$ as a promising platform for exploring topological superconductivity.

cond-mat.str-el↗

arXiv2026

Tunable Interlayer Charge-transfer States in MoSe$_2$/WS$_2$ Moir\'e Superlattices

Moir\'e superlattices formed by transition metal dichalcogenide (TMD) heterobilayers provide a versatile platform for studying strongly correlated electronic, excitonic, and topological phenomena in solids. In particular, angle-aligned MoSe$_2$/WS$_2$ heterobilayers, which have a Type-I band alignment at zero vertical electric field, host rich correlated spin and charge physics. Here, combining large-scale first-principles calculations and optical reflection spectroscopy, we report a thorough study of the emergent moir\'e excitonic states and interlayer charge-transfer states in angle-aligned electron-doped MoSe$_2$/WS$_2$ moir\'e superlattices. The moir\'e excitonic states serve as sensitive optical probes to the localization profile of doped electrons. We observe a series of interlayer charge-transfer transitions from n/n$_0$ = 1 to 4 (where n$_0$ denotes the moir\'e density) when the vertical electric field switches the heterostructure band alignment from Type-I to Type-II. By tuning the vertical electric field, we can precisely control the interlayer electron localization, realizing a Fermi-Hubbard model with a tunable charge-transfer band on an effective honeycomb lattice. Furthermore, Monte Carlo simulation of the doping dependence of the electric-field susceptibility predicts that multiple correlated charge-ordered states appear at both integer and fractional fillings. Our results provide a holistic understanding of the emergent optical excitations and the correlated charge-transfer states in electron-doped MoSe$_2$/WS$_2$ moir\'e superlattices.

cond-mat.mes-hall↗

arXiv2026

Signatures of moir\'e intralayer biexcitons and exciton-phason coupling in WSe2/WS2 heterostructures

Interactions among electronic and lattice degrees-of-freedom are foundational to various phases in condensed-matter physics, yet the dynamic interplay between excitonic and phononic quasiparticles represents an equivalent, underexplored frontier. Moir\'e superlattices provide an ideal platform for realizing these interactions by offering localized intralayer excitons (IALX) and ultralow-energy collective lattice modes, such as phasons. Here, by optically suppressing ultrafast charge-transfer (CT) to interlayer excitons in WSe2/WS2 heterostructures, we uncover dynamics of moir\'e IALX revealing long lifetimes ({\tau} > 1000 ps) arising from localized Wannier and in-plane CT nature. We then observe moir\'e intralayer intervalley biexcitons with binding energy ~ 16 meV, with long lifetimes due to moir\'e confinement. Furthermore, we find time-domain signatures of strong coupling between moir\'e-IALX and ~ 10 micro-eV phasons, evidenced as twist-angle-dependent GHz oscillations in IALX dynamics. Our findings establish moir\'e superlattices as interacting hybrid quantum systems and for engineering non-equilibrium phenomena, as well as for GHz-scale optoelectronics.

cond-mat.mes-hall↗

arXiv2025

Imaging Electron-Hole Asymmetry in the Quantum Melting of Generalized Wigner Crystals

Two-dimensional moir\'e materials provide a versatile platform to explore phase transitions in strongly correlated systems. Using scanning tunneling microscopy (STM) we have imaged the density-driven melting of generalized Wigner crystals (GWCs) and Mott insulators (MIs) in electron-doped, near-60{\deg} twisted MoSe2 bilayers featuring a triangular moir\'e superlattice. We observe striking electron-hole asymmetry in GWC melting: hole-doped GWCs yield interaction-driven disordered states whereas electron-doped GWCs melt into delocalized liquid-like states. This asymmetry arises from the broken particle-hole symmetry of the moir\'e superlattice, which produces electron and hole Fermi pockets with different momentum geometries upon GWC condensation. MI states melt without such asymmetry, consistent with the absence of a symmetry-breaking density modulation. This work provides direct visualization of the novel emergent phases that appear as GWCs undergo quantum melting transitions.

cond-mat.str-el↗