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Introduction：
Introduction：
I am a postdoctoral researcher at the University of Manchester. My current research focuses on developing high-quality devices from van der Waals quantum materials for future electronics. Please see my CV or Google Scholar profile for details.
I am currently seeking faculty positions and would sincerely appreciate any information regarding relevant opportunities.
E-mail: zefeiw@gmail.com
Address: National Graphene Institute, University of Manchester, M13 9PL, UK
Research highlights:
Research highlights:
I. Record-high-mobility 2D electronic devices
⭕ Extraordinary electronic quality in proximity screened graphene
Electronic quality is crucial for probing quantum transport, with GaAlAs heterostructures long holding the record after decades of optimization that pushed mobilities to ~5.7 × 10⁷ cm² V⁻¹ s⁻¹. Graphene has progressed from ~10⁴ cm² V⁻¹ s⁻¹ on Si wafers to ~10⁵ and then ~10⁶ cm² V⁻¹ s⁻¹ in suspended and hBN-encapsulated devices respectively, though its low-temperature mobility has been limited by edge scattering and charge inhomogeneity. In collaboration with Prof. Andre Geim, I successfully fabricated devices with graphite proximity gate positioned just 1 nm from graphene. This approach reducs charge inhomogeneity by nearly two orders of magnitude, enabling quantum mobilities of ~10⁷ cm² V⁻¹ s⁻¹ and record transport mobilities exceeding 10⁸ cm² V⁻¹ s⁻¹. This breakthrough allows phenomena such as Shubnikov–de Haas oscillations and the quantum Hall effect to emerge at ultra-low magnetic fields, providing a powerful platform for studying many-body physics in previously inaccessible regimes.
Proximity screening greatly enhances electronic quality of graphene,
Nature 644, 646–651 (2025).
⭕ On-device phase-engineering for record-high-mobility 2D semiconductors
Forming good electrical contacts with atomically thin transition metal dichalcogenide semiconductors (TMDSCs) is difficult due to interfacial barriers. This work introduces an approach that uses interfacial bonding distortion to achieve nearly barrier-free contacts, enabling efficient carrier injection and stable ohmic behavior from room to cryogenic temperatures. The resulting TMDSC transistors demonstrate ultra-low contact resistance (as low as 90 Ω µm, towards the quantum limit), exceptionally high mobility (up to 358,000 cm²V⁻¹s⁻¹), and excellent cryogenic transport properties. Beyond improving contacts, the method allows local tuning of atomic and electronic structures for advanced TMDSC device engineering.
Bridging the gap between atomically thin semiconductors and metal leads, Nature Communications 13, 1777 (2022).
II. Valley physics in 2D electronic devices
⭕ Probe the valley Hall effect using purely electronic means
This work reports the first experimental observation of intrinsic valley Hall effect (VHE) in odd-layer MoS₂ without the need of extrinsic symmetry breaking. Nonlocal transport measurements reveal a cubic scaling of nonlocal resistance with local resistance in monolayer and trilayer devices, consistent with VHE driven by Berry curvatures at inequivalent valleys. The effect persists up to room temperature, with micron-scale valley diffusion lengths. These findings establish odd-layer TMDCs as an ideal platform for topological valley transport and open pathways toward electrically controlled, low-dissipation valleytronics.
Intrinsic valley Hall transport in atomically thin MoS₂,
⭕ Quantum Hall and valley Zeeman effects in Q-valley electrons
This work reports quantum transport studies of Q-valley electrons in few-layer transition metal disulfides (TMDs), enabled by high-mobility BN-encapsulated devices with optimized contacts. Pronounced Shubnikov–de Haas oscillations and the onset of quantum Hall plateaus are observed, revealing distinct Zeeman responses: a valley Zeeman effect in odd-layer TMDs and a spin Zeeman effect in even-layer TMDs. These contrasting behaviors arise from the presence or absence of inversion symmetry, which dictates spin–valley coupling at the Q valleys. The results extend the unique spin–valley physics of monolayer TMDs to few-layer systems, providing new insights into multi-valley band structures and unconventional quantum Hall effects.
Even–odd layer-dependent magnetotransport of high-mobility Q-valley electrons in transition metal disulfides,
III. Nonlinear transport in 2D electronic devices
⭕ Electric-field control of the Berry curvature dipole
This work reports the intrinsic nonlinear Hall effect in twisted bilayer graphene (TBG), arising from a Berry curvature dipole within its flatbands. Unlike extrinsic effects caused by disorder scattering in other graphene superlattices, the observed second harmonic Hall voltage here directly reflects the intrinsic Berry curvature distribution. Applying a displacement field shifts the Berry curvature hotspots, enabling tunable direction and amplitude of the nonlinear Hall response. These results demonstrate that high-quality TBG serves as a sensitive platform for probing Berry curvature and for potential applications in second harmonic generation and rectification.
Intrinsic nonlinear Hall effect and gate-switchable Berry curvature sliding in twisted bilayer graphene,
Physical Review Letters 131, 066301 (2023) editors' suggestion.
⭕ Giant nonlinear Hall effect induced by interaction effects
This study demonstrates a giant nonlinear Hall effect (NHE) in twisted WSe₂ bilayers, enabled by moiré flat bands and strong electron correlations. At half-filling of the first moiré band, the NHE signal peaks sharply, showing a generation efficiency over two orders of magnitude higher than previously reported materials. The enhancement is closely tied to correlation-driven phenomena, with resistivity data suggesting a mass-diverging continuous Mott transition near the insulating state. These findings highlight how moiré engineering can combine Berry curvature dipoles with interaction effects to generate novel quantum responses and establish NHE as a powerful probe of quantum criticality.
Giant nonlinear Hall effect in twisted bilayer WSe₂,
National Science Review 10, nwac232 (2023). ESI highly cited paper.
IV. Functional 2D electronic devices
⭕ 2D semiconductors for functional flexible devices
This study demonstrates that monolayer graphene oxide (GO) membranes are simultaneously impermeable to gases and highly conductive to protons across the basal plane. Contrary to the common assumption of abundant nanoscale pinholes, micrometer-scale GO areas show no helium leakage while exhibiting proton conductivity nearly two orders of magnitude higher than graphene. The enhanced transport originates from oxygen functional groups that distort the graphene lattice and create abundant active sites for proton passage. These findings highlight how chemical functionalization can be harnessed to boost proton transparency of 2D crystals without sacrificing gas impermeability, offering pathways for advanced proton exchange membranes.
Proton and molecular permeation through the basal plane of monolayer graphene oxide,
Nature Communications 14, 7756 (2023).
⭕ Sliding ferroelectric devices based on marginally twisted 2D semiconductors
Robust room-temperature ferroelectricity was reported in marginally twisted MoS₂ heterostructures, arising from broken inversion symmetry and interfacial charge transfer at the twisted bilayer interface. In this work, I contribute marginally twisted bilayer MoS₂ ferroelectric devices, which exhibit pronounced hysteresis behavior of the conductivity when tuning the gate voltages (shown in the right figure). It is the first semiconducting sliding ferroelectric field-effect transistor that has ever been reported.
Interfacial ferroelectricity in marginally twisted 2D semiconductors,
Nature Nanotechnology 17, 390–395 (2022).
Device image gallery：
Device image gallery：
🔸 Graphene quantum capacitor
🔸Monolayer MoS2 valley Hall transistor
🔸Twisted bilayer WSe2 nonlinear Hall device
🔸Double-layer MoS2 FET with Corbino geometry
🔸Double-layer WSe2 FET with Hall bar geometry
🔸Dark-field optical image of a Hall bar device
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