Publications
Domain-Dependent Surface Adhesion in Twisted Few-Layer Graphene: Platform for Moiré-Assisted Chemistry
Twisted van der Waals multilayers are widely regarded as a rich platform to access novel electronic phases thanks to the multiple degrees of freedom available for controlling their electronic and chemical properties. Here, we propose that the stacking domains that form naturally due to the relative twist between successive layers act as an additional ”knob” for controlling the behavior of these systems and report the emergence and engineering of stacking domain-dependent surface chemistry in twisted few-layer graphene.
Structural evolution of the kagome superconductors A V3Sb5 (A = K, Rb, and Cs) through charge density wave order
The kagome superconductors KV3Sb5, RbV3Sb5, and CsV3Sb5 are known to display charge density wave (CDW) order which impacts the topological characteristics of their electronic structure. Details of their structural ground states and how they evolve with temperature are revealed here using single crystal x-ray crystallographic refinements as a function of temperature, carried out with synchrotron radiation. The compounds KV3Sb5 and RbV3Sb5 present 2×2×2 superstructures in the Fmmm space group with a staggered trihexagonal deformation of vanadium layers.
Melting of generalized Wigner crystals in transition metal dichalcogenide heterobilayer Moiré systems (Nature Communications, (2022), 13, 1, (7098), 10.1038/s41467-022-34683-x)
The original version of this Article contained an error in the Acknowledgements, which incorrectly read ‘The authors acknowledge support by the NSF [Platform for the Accelerated Realization, Analysis, and Discovery of Interface Materials (PARADIM)] under cooperative agreement no. DMR-U638986.’. The correct version states ‘DMR-1539918’ in place of ‘DMRU638986’. This has been corrected in both the PDF and HTML versions of the Article. © The Author(s) 2023.
Machine learning discovery of new phases in programmable quantum simulator snapshots
Machine learning has recently emerged as a promising approach for studying complex phenomena characterized by rich datasets. In particular, data-centric approaches lead to the possibility of automatically discovering structures in experimental datasets that manual inspection may miss. Here, we introduce an interpretable unsupervised-supervised hybrid machine learning approach, the hybrid-correlation convolutional neural network (hybrid-CCNN), and apply it to experimental data generated using a programmable quantum simulator based on Rydberg atom arrays.
Melting of generalized Wigner crystals in transition metal dichalcogenide heterobilayer Moiré systems
Moiré superlattice systems such as transition metal dichalcogenide heterobilayers have garnered significant recent interest due to their promising utility as tunable solid state simulators. Recent experiments on a WSe2/WS2 heterobilayer detected incompressible charge ordered states that one can view as generalized Wigner crystals. The tunability of the transition metal dichalcogenide heterobilayer Moiré system presents an opportunity to study the rich set of possible phases upon melting these charge-ordered states.
Fractional correlated insulating states at one-third filled magic angle twisted bilayer graphene
The observation of superconductivity and correlated insulating states in twisted bilayer graphene has motivated much theoretical progress at integer fillings. However, little attention has been given to fractional fillings. Here we show that the three-peak structure of Wannier orbitals, dictated by the symmetry and topology of flat bands, facilitates the emergence of a state we name a “fractional correlated insulator” at commensurate fractional filling of ν = n ± 1/3.
Hamiltonian reconstruction as metric for variational studies
Variational approaches are among the most powerful techniques to approximately solve quantum many-body problems. These encompass both variational states based on tensor or neural networks, and parameterized quantum circuits in variational quantum eigensolvers. However, self-consistent evaluation of the quality of variational wavefunctions is a notoriously hard task. Using a recently developed Hamiltonian reconstruction method, we propose a multi-faceted approach to evaluating the quality of neural-network based wavefunctions.
Harnessing interpretable and unsupervised machine learning to address big data from modern X-ray diffraction
The information content of crystalline materials becomes astronomical when collective electronic behavior and their fluctuations are taken into account. In the past decade, improvements in source brightness and detector technology atmodern X-ray facilities have allowed a dramatically increased fraction of this information to be captured. Now, the primary challenge is to understand and discover scientific principles from big datasets when a comprehensive analysis is beyond human reach.
Quantum Phases of Transition Metal Dichalcogenide Moiré Systems
Moiré systems provide a rich platform for studies of strong correlation physics. Recent experiments on heterobilayer transition metal dichalcogenide Moiré systems are exciting in that they manifest a relatively simple model system of an extended Hubbard model on a triangular lattice. Inspired by the prospect of the hetero-transition metal dichalcogenide Moiré system's potential as a solid-state-based quantum simulator, we explore the extended Hubbard model on the triangular lattice using the density matrix renormalization group.
Strong interlayer interactions in bilayer and trilayer moire superlattices
Moire superlattices constructed from transition metal dichalcogenides have demonstrated a series of emergent phenomena, including moire excitons, flat bands, and correlated insulating states. All of these phenomena depend crucially on the presence of strong moire potentials, yet the properties of these moire potentials, and the mechanisms by which they can be generated, remain largely open questions. Here, we use angle-resolved photoemission spectroscopy with submicron spatial resolution to investigate an aligned WS2/WSe2moire superlattice and graphene/WS2/WSe2trilayer heterostructure.