Tse-Ming Chen

Quantum geometry encodes how Bloch wavefunctions change across momentum space, endowing electronic bands with length, phase, and response scales beyond their dispersion. In this Editorial, we outline how quantum geometry shapes the modern condensed matter phenomena, including linear and nonlinear transport, optical selection rules, collective modes, fractional Chern phases, flatband superconductivity, magnetism, and many-body quantum information. We present the organizing principles for designing, interpreting, and harvesting electronic responses in quantum materials with nontrivial Bloch-state texture.

Twisted bilayer graphene near the quasicrystalline twist angle reveals strong interlayer coupling and an anomalous fourfold-to-twelvefold Landau-level transition in electron transport.

Advances in atomically thin two‐dimensional materials have created new opportunities to regulate interfacial charge transfer and surface reactivity in electrocatalysis. Among anodic reactions relevant to sustainable energy conversion, the iodide oxidation reaction (IOR) has emerged as an attractive alternative to the oxygen evolution reaction because of its lower overpotential, faster kinetics, and simultaneous generation of value‐added iodine species. Here, by using scanning electrochemical cell microscopy, we show that the electronic structure of graphene can be engineered to promote IOR through two experimentally distinct routes: electrostatic gating in monolayer graphene and twist‐angle control in bilayer graphene. Gate‐dependent measurements show that hole doping promotes iodide oxidation, whereas electron doping suppresses it, consistent with Fermi‐level modulation of electron extraction from iodide. Magic‐angle twisted bilayer graphene (MATBG) exhibits a lower onset potential and stronger IOR response than monolayer and Bernal‐stacked bilayer graphene. The enhanced activity of MATBG is associated with a moiré‐reconstructed interfacial electronic environment that facilitates IOR. These results establish electronic‐structure engineering of graphene as an effective strategy for regulating nanoscale iodide oxidation and highlight Dirac‐cone engineering as a tunable platform for sustainable iodine redox electrochemistry.

Among two-dimensional semiconductors, tungsten diselenide (WSe₂) is particularly suitable for monolithic complementary metal-oxide-semiconductor (CMOS) architectures due to its tunable carrier polarity. Surface oxidation has emerged as a simple and effective route to control polarity and enhance p-type behavior; however, despite its widespread use, fundamental characterization of the oxide-induced electrostatic landscape in WSe₂ remains limited. Here, we employ surface oxidation and selective-area oxide removal to form a lateral junction within few-layer WSe₂. We apply a modified broadband electrostatic force microscopy technique to map nanoscale capacitance variations, providing contact-free insight into local carrier dynamics analogous to conventional MOS C-V measurements, probing oxide-induced electronic effects beyond conventional spectroscopy methods. Bias-dependent measurements reveal a distinct p-n junction between oxidized and oxide-removed regions, with a built-in surface potential difference of approximately 120 meV measured by Kelvin probe force microscopy, demonstrating spatially controlled polarity engineering without heterogeneous material integration. Field-effect transistors fabricated on the n- and p-regions integrated into a complementary inverter circuit exhibit ultralow peak static power consumption ∼13 pW at V_D = 1 V, among the lowest reported for WSe₂-based logic circuits. We demonstrate self-powered photovoltaic photodetection resulting from the in-built electric field of the p-n junction, with fast, reproducible submillisecond response, symmetric rise and fall times, linear current-power dependence, and minimal charge trapping─key metrics for robust and reliable photodetection. Together, these results establish oxide-defined lateral p-n junctions in WSe₂ as a compelling platform for reliable, ultralow-power electronic and optoelectronic applications.

Moiré superlattices, arising from overlaying atomic layers with slight mismatch or rotation, have transformed the study of emergent electronic and quantum phenomena beyond those of the constituent materials. Expanding this paradigm, here we demonstrate moiré superlattice formation at the interface between strongly correlated oxides and two-dimensional layered materials. The integration of complex oxides, a classic family of strongly correlated electron systems with transition metal dichalcogenides, enables the realization of an emerging class of moiré-engineered heterostructures that may potentially extend beyond conventional van der Waals systems. Herein, we reveal the presence of moiré superlattices in oxide-WS₂ heterostructures across varying twist angles and demonstrate highly tunable moiré periodicity as well as ultrafast charge transfer in these oxide-transition metal dichalcogenide systems. Direct observation of moiré exciton minibands confirms the emergence of moiré electronic structures, enabling twist-tunable discrete quantum states and unconventional charge dynamics. In combination with continuum modeling and density functional theory, our results elucidate the intricate interplay between moiré periodicity, quantum confinement, and band-flattening effects. By harnessing the synergy between complex oxides and layered materials, this work establishes a versatile platform for engineering artificial quantum states, providing previously inaccessible insights into correlated quantum phenomena and quantum material engineering.

The precise nature of Kondo spins has remained enigmatic when extended to multiple spin impurities or, more intriguingly, when the localized spin itself may already be the consequence of many-body interactions in a presumably delocalized open nanoconstriction, such as a quantum point contact (QPC). It is experimentally challenging to distinguish the Kondo state from other coexisting many-body spin states in such a strongly correlated system. Here we lithographically define an all-on-chip electronic resonator (ER) and a QPC in a high-mobility GaAs/AlGaAs heterostructure transistor. Local Kondo screening of the QPC spin and nonlocal spin singlet across the ER-QPC integration is controllable in response to ER occupancy parity. We also show that the 0.7 anomaly, another strongly correlated state in QPCs, not only has a different physical origin but furthermore counteracts the Kondo spin singlet. These results demonstrate a noninvasive quantum method for sensing spontaneous magnetic impurities within an open nanoconstriction.

Ferroelectricity realized in van der Waals (vdW) materials with non‐centrosymmetric stacking configurations holds promise for future 2D devices with nonvolatile and reconfigurable functionalities. However, the epitaxial growth of ferroelectric vdW materials often struggles to achieve an energetically unfavorable stacking configuration that enables electric polarization. This challenge is particularly evident when performing heteroepitaxy on another vdW substrate to create versatile and scalable ferroelectric building blocks designed for large‐area, atomic‐scale thicknesses. Here, epitaxial hexagonal boron nitride (h‐BN) multilayer films are successfully grew on single‐crystal graphene synthesized on a miscut SiC (0001) substrate. Theoretical calculations illustrate that the moiré‐patterned h‐BN/graphene hetero‐interface intrinsically exhibits polarization, leading to a polarized AB stacking in multilayer h‐BN films to minimize the total formation energy, which is validated experimentally by the layer‐dependent band dispersions. The as‐grown multilayer h‐BN layers demonstrated robust, homogeneous ferroelectricity with switchable out‐of‐plane polarization via interlayer sliding. This study establishes an effective route for stacking‐controlled heteroepitaxy, enabling the large‐scale integration of vdW materials with ferroelectricity and versatile functionalities, offering a promising platform for next‐generation 2D ferroelectric devices.

Strain engineering has quickly emerged as a viable option to modify the electronic, optical and magnetic properties of 2D materials. However, it remains challenging to arbitrarily control the strain. Here we show that by creating atomically-flat surface nanostructures in hexagonal boron nitride, we achieve an arbitrary on-chip control of both the strain distribution and magnitude on high-quality molybdenum disulfide. The phonon and exciton emissions are shown to vary in accordance with our strain field designs, enabling us to write and draw any photoluminescence color image in a single chip. Moreover, our strain engineering offers a powerful means to significantly and controllably alter the strengths and energies of interlayer excitons at room temperature. This method can be easily extended to other material systems and offers a promise for functional excitonic devices.

Epitaxial growth is of significant importance over the past decades, given it has been the key process of modern technology for delivering high-quality thin films. For conventional heteroepitaxy, the selection of proper single crystal substrates not only facilitates the integration of different materials but also fulfills interface and strain engineering upon a wide spectrum of functionalities. Nevertheless, the lattice structure, regularity and crystalline orientation are determined once a specific substrate is chosen. Here, we reveal the growth of twisted oxide lateral homostructure with controllable in-plane conjunctions. The twisted lateral homostructures with atomically sharp interfaces can be composed of epitaxial “blocks” with different crystalline orientations, ferroic orders and phases. We further demonstrate that this approach is universal for fabricating various complex systems, in which the unconventional physical properties can be artificially manipulated. Our results establish an efficient pathway towards twisted lateral homostructures, adding additional degrees of freedom to design epitaxial films.