A5019679209- Graphene research and applications
- 2D Materials and Applications
- Quantum and electron transport phenomena
- Topological Materials and Phenomena
- MXene and MAX Phase Materials
- Diamond and Carbon-based Materials Research
- Mechanical and Optical Resonators
- Semiconductor materials and devices
- Boron and Carbon Nanomaterials Research
- Chalcogenide Semiconductor Thin Films
- Advanced MEMS and NEMS Technologies
- Force Microscopy Techniques and Applications
- Magnetic properties of thin films
- Molecular Junctions and Nanostructures
- Advanced Thermoelectric Materials and Devices
- Semiconductor materials and interfaces
- Organic Electronics and Photovoltaics
- Machine Learning in Materials Science
- Advancements in Semiconductor Devices and Circuit Design
- Industrial Automation and Control Systems
- Plasmonic and Surface Plasmon Research
- Interactive and Immersive Displays
- Modular Robots and Swarm Intelligence
- Nanopore and Nanochannel Transport Studies
- Low-power high-performance VLSI design
Stanford University
2019-2024
SLAC National Accelerator Laboratory
2021-2024
Lancaster University
2023
Institute of Photonic Sciences
2019
University of California, Berkeley
2019
When two sheets of graphene are stacked at a small twist angle, the resulting flat superlattice minibands expected to strongly enhance electron-electron interactions. Here we present evidence that near three-quarters ($3/4$) filling conduction miniband these enhanced interactions drive twisted bilayer into ferromagnetic state. We observe emergent hysteresis, with giant anomalous Hall (AH) effect as large $10.4\ \mathrm{k\Omega}$ and signs chiral edge states in narrow density range around an...
We have previously reported ferromagnetism evinced by a large hysteretic anomalous Hall effect in twisted bilayer graphene (tBLG). Subsequent measurements of quantized resistance and small longitudinal confirmed that this magnetic state is Chern insulator. Here we report that, when tilting the sample an external field, highly anisotropic. Because spin-orbit coupling negligible such anisotropy unlikely to come from spin, but rather favors theories which orbital. know no other case has purely...
We present transport measurements of bilayer graphene with 1.38{\deg} interlayer twist and apparent additional alignment to its hexagonal boron nitride cladding. As other devices angles substantially larger than the magic angle 1.1{\deg}, we do not observe correlated insulating states or band reorganization. However, several highly unusual behaviors in magnetotransport. For a large range densities around half filling moir\'e bands, magnetoresistance is quadratic. Over these same densities,...
Anisotropic hopping in a toy Hofstadter model was recently invoked to explain rich and surprising Landau spectrum measured twisted bilayer graphene away from the magic angle. Suspecting that such anisotropy could arise unintended uniaxial strain, we extend Bistritzer–MacDonald include heterostrain present detailed analysis of its impact on band structure magnetotransport. We find strain strongly influences structure, shifting three otherwise-degenerate van Hove points different energies....
In a stack of atomically thin van der Waals layers, introducing interlayer twist creates moiré superlattice whose period is function angle. Changes in that angle even hundredths degree can dramatically transform the system’s electronic properties. Setting precise and uniform for remains difficult; hence, determining mapping its spatial variation very important. Techniques have emerged to do this by imaging moiré, but most these require sophisticated infrastructure, time-consuming sample...
The electronic properties of moiré heterostructures depend sensitively on the relative orientation between layers stack. For example, near-magic-angle twisted bilayer graphene (TBG) commonly shows superconductivity, yet a TBG sample with one rotationally aligned to hexagonal Boron Nitride (hBN) cladding layer provided experimental observation orbital ferromagnetism. To create samples graphene/hBN, researchers often align edges exfoliated flakes that appear straight in optical micrographs....
We present the design and implementation of a measurement system that enables parallel drive detection small currents voltages at numerous electrical contacts to multi-terminal device. This system, which we term feedback lock-in, combines digital control-loop with software-defined lock-in measurements dynamically source measure small, pre-amplified potentials. The effective input impedance each current/voltage probe can be set via software, permitting any given contact behave as an...
The electronic properties of moir\'e heterostructures depend sensitively on the relative orientation between layers stack. For example, near-magic-angle twisted bilayer graphene (TBG) commonly shows superconductivity, yet a TBG sample with one rotationally aligned to hexagonal Boron Nitride (hBN) cladding layer provided first experimental observation orbital ferromagnetism. To create samples graphene/hBN, researchers often align edges exfoliated flakes that appear straight in optical...
Scanning probe techniques are popular, non-destructive ways to visualize the real space structure of Van der Waals moir\'es. The high lateral spatial resolution provided by these enables extracting moir\'e lattice vectors from a scanning image. We have found that extracted values, while precise, not necessarily accurate. Scan-to-scan variations in behavior piezos which drive probe, and thermally-driven slow relative drift between sample, produce systematic errors extraction vectors. In this...
Scanning probe techniques are popular, nondestructive ways to visualize the real space structure of Van der Waals moirés. The high lateral spatial resolution provided by these enables extracting moiré lattice vectors from a scanning image. We have found that extracted values, while precise, not necessarily accurate. Scan-to-scan variations in behavior piezos drive and thermally driven slow relative drift between sample produce systematic errors extraction vectors. In this Letter, we identify...
We present CircuitGlue, an electronic converter board that allows heterogeneous components to be readily interconnected. Electronic are plugged into eight-pin programmable header on the board, and assignment of each pin in is configured software. CircuitGlue supports a variety connections, including power, ground, analog signals, various digital protocols at different voltages. As such, off-the-shelf modules instantly compatible no matter what voltage levels, interface types, communication...
Anisotropic hopping in a toy Hofstadter model was recently invoked to explain rich and surprising Landau spectrum measured twisted bilayer graphene away from the magic angle. Suspecting that such anisotropy could arise unintended uniaxial strain, we extend Bistritzer-MacDonald include heterostrain. We find strain strongly influences band structure, shifting three otherwise-degenerate van Hove points different energies. Coupled Boltzmann magnetotransport calculation, this reproduces...
In a stack of atomically-thin Van der Waals layers, introducing interlayer twist creates moir\'e superlattice whose period is function angle. Changes in that angle even hundredths degree can dramatically transform the system's electronic properties. Setting precise and uniform for remains difficult, hence determining mapping its spatial variation very important. Techniques have emerged to do this by imaging moir\'e, but most these require sophisticated infrastructure, time-consuming sample...