Research

Research Interests

A central challenge in contemporary condensed matter physics is to understand how strongly interacting and topologically entangled electrons give rise to new forms of quantum matter. Van der Waals materials, particularly two-dimensional systems, provide an exceptionally tunable platform for discovering and controlling these emergent phases. My research explores these systems through complementary approaches, including top-down mesoscopic device assembly and fabrication, and bottom-up atomic-scale materials engineering by molecular beam epitaxy. Using scanning tunneling microscopy, spectroscopy, and quantum transport, I investigate the microscopic origins of emergent quantum states and develop new ways to manipulate them.

Imaging Quasiparticles in Quantum Hall Systems

Quantum Hall phases provide a clean platform where strong interactions produce emergent quasiparticles that are fundamentally different from electrons, including skyrmions and fractionally charged anyons. Direct real-space probes of individual quantum Hall quasiparticles are essential for understanding their structure and interactions, how they are bound and stabilized, and how they might ultimately be manipulated for topological quantum computing.

In my postdoctoral work, we developed a delicate STM measurement protocol for gated monolayer graphene quantum Hall systems, designed to minimize tip-induced perturbations. By controlling the impurity potential and Landau-level filling, we directly imaged split Landau orbitals, integer quantum Hall quasiparticles, and localized multi-anyon states.

Real-space Imaging of Quantum Hall Quasiparticles
J. Deng*, Y. Sun*, et al. arXiv:2606.25036

*Real-space spectral density profile of three-anyon bound state*

Correlated Phases in Rhombohedral Multilayer Graphene

Rhombohedral multilayer graphene provides an exceptionally tunable platform in which superconductivity, orbital magnetism, electronic crystallization, and Fermi-surface reconstruction can emerge from the same interacting electron system.

In my postdoctoral work, we mapped a rich phase diagram in rhombohedral hexalayer graphene using quantum transport measurements, revealing multiple unconventional superconducting phases and multiferroic behavior arising from intertwined symmetry-breaking orders. More strikingly, we carried out STM measurement and identified an unexpected metallic electron crystal and an oblique-to-honeycomb quantum phase transition in rhombohedral hexalayer graphene.

These discoveries motivate a broader research program that combines local spectroscopy, electrostatic control, and complementary transport measurements to determine how competing quantum orders emerge, coexist, and transform at the microscopic scale.

Superconductivity and ferroelectric orbital magnetism in semimetallic rhombohedral hexalayer graphene
J. Deng*, J. Xie*, H. Li*, et al. arXiv:2508.15909

Magnetic-field-induced superconductivity in hexalayer rhombohedral graphene
J. Deng, et al. arXiv:2603.13498

*A quantum transport phase diagram in rhombohedral hexalayer graphene*

Creating and Engineering New Quantum Materials

When van der Waals materials are reduced to the one- or two-dimensional limit, enhanced interactions and reduced dimensionality can stabilize phases that are absent in their bulk counterparts. Their weak interlayer bonding also enables atomically precise assembly of materials with different structures and functionalities, providing new opportunities to engineer electronic, magnetic, and collective quantum states.

During my Ph.D., we used molecular beam epitaxy and scanning tunneling microscopy to create and investigate low-dimensional quantum materials, including correlated W₆Te₆ and Nb₆Te₆ atomic wires, organic–semiconductor heterostructures with interlayer hybridization, and VCl₃/NbSe₂ heterostructures exhibiting interface-induced ferroelectric behavior.

Alternating-chiral charge density waves and associated spin polarization in monolayered NbTe₂
Y. Bai*, G. Cao*, H. Zhang*, J. Deng*, et al. Nature Communications (2026). https://doi.org/10.1038/s41467-026-75813-z

Evidence of ferroelectricity in an antiferromagnetic vanadium trichloride monolayer
J. Deng*, D. Guo*, Y. Wen*, S. Lu*, et al. Science Advances 11 (10), eado6538 (2025)

van der Waals Engineering of Charge Density Waves in One-Dimensional Nb₆Te₆ Nanowires
X. Lin*, J. Deng*, Y. Bai*, et al. ACS Nano 18 (20), 13241-13248 (2024)

Observations of Charge-Density-Wave States in W₆Te₆ Wires
J. Deng, et al. Nano Letters 23 (17), 7831-7837 (2023)

Band alignment and interlayer hybridization in monolayer organic/WSe₂ heterojunction
Y. Guo*, L. Wu*, J. Deng*, et al. Nano Research 15 (2), 1276-1281 (2022)

Precise Tuning of Band Structures and Electron Correlations by van der Waals Stacking of One-dimensional W₆Te₆ Wires
J. Deng, et al. Nano Letters 20 (12), 8866-8873 (2020)