Related Experiment Video
Updated: Jul 5, 2025
13:56
Probe Type II Band Alignment in One-Dimensional Van Der Waals Heterostructures Using First-Principles Calculations
Published on: October 12, 2019
7.6K
Tuning commensurability in twisted van der Waals bilayers.
Yanxing Li1, Fan Zhang1, Viet-Anh Ha1,2
1Department of Physics, The University of Texas at Austin, Austin, TX, USA.
Nature
|January 17, 2024
Summary
Large-angle twisted transition metal dichalcogenide bilayers create novel moiré patterns, including quasicrystals and commensurate crystals. These structures exhibit unique electronic behaviors, opening new avenues in moiré physics.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Nanotechnology
Background:
- Moiré superlattices are typically formed in van der Waals bilayers at small twist angles, resulting in long-wavelength patterns with approximate translational symmetry.
- At large twist angles, moiré patterns are generally incommensurate, with exceptions at specific discrete angles.
Purpose of the Study:
- To investigate the distinct platforms offered by large-angle twisted bilayers.
- To explore the creation and electronic properties of moiré patterns at large twist angles in tungsten diselenide bilayers.
Main Methods:
- Fabrication of twisted tungsten diselenide bilayers with large twist angles.
- Utilized valley-resolved scanning tunneling spectroscopy to probe electronic structures.
Main Results:
- Successfully created incommensurate dodecagon quasicrystals at a twist angle of 30°.
- Synthesized commensurate moiré crystals at twist angles of 21.8° and 38.2°.
- Observed distinct electronic behaviors between moiré crystals and quasicrystals, including mini-gap formation in the K valley near the valence band maximum.
Conclusions:
- Large-angle twisted bilayers provide a versatile platform for generating diverse moiré patterns, including quasicrystals.
- These systems exhibit unique electronic properties, differing significantly from small-angle moiré structures.
- This work expands the design space for exploring novel moiré physics beyond traditional small-angle regimes.
Related Concept Videos
01:22Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)
1.1K
Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the...
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the...
1.1K
01:08Spin–Spin Coupling Constant: Overview
924
In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must...
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must...
924
01:09Theories of Dissolution: The Danckwerts' Model and Interfacial Barrier Model
303
Various dissolution theories provide insight into the factors that influence the dissolution rate. Danckwerts' Model suggests that turbulence, rather than a stagnant layer, characterizes the dissolution medium at the solid-liquid interface. In this model, the agitated solvent contains macroscopic packets that move to the interface via eddy currents, facilitating the absorption and delivery of the drug to the bulk solution. The regular replenishment of solvent packets maintains the...
303
01:31Dielectric Polarization in a Capacitor
4.7K
The presence of a dielectric medium in a capacitor not only changes the voltage and capacitance but also affects the electric field. In general, dielectrics can be of two types: polar and nonpolar. In a polar dielectric, the positive and negative charges in the molecules are separated by a distance and hence have a permanent dipole moment. In contrast, no such charge separation exists in a nonpolar dielectric, however the nonpolar molecules get polarized in the presence of an external electric...
4.7K
01:19Equivalent Capacitance
1.4K
Multiple capacitors can be connected in a circuit in series or parallel configuration. When the capacitor combination is connected to a battery, the potential drop across each capacitor and the magnitude of charge stored in the individual capacitor depends on the type of the connection. The capacitor combination is replaced by a single equivalent capacitor that stores the same amount of charge as the combination for a given potential difference.
The following strategies are adopted to calculate...
The following strategies are adopted to calculate...
1.4K
01:02¹H NMR: Interpreting Distorted and Overlapping Signals
1.0K
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are...
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are...
1.0K