Programmable Re-entrant Topological Polaritons in Graphene Grating/α-MoO3 Heterostructure.
Hanchao Teng1,2,3, Chengyu Jiang1,2, Min Liu1,2
1CAS Key Laboratory of Nanophotonic Materials and Devices, CAS Key Laboratory of Standardization and Measurement for Nanotechnology, National Center for Nanoscience and Technology, Beijing 100190, P. R. China.
Nano Letters
|January 26, 2026
Summary
Researchers developed a novel graphene/α-MoO3 heterostructure for active control of polariton topology. This platform enables dynamic, multistate switching between hyperbolic and elliptic phases, crucial for reconfigurable nanophotonics.
Area of Science:
- Condensed Matter Physics
- Nanophotonics
- Materials Science
Background:
- Active control of polariton topology is essential for advanced nanophotonic devices.
- Current platforms face limitations due to material structures and restricted tuning.
Purpose of the Study:
- To introduce a new graphene grating/α-MoO3 heterostructure for tunable polariton topology.
- To demonstrate doping-driven topological transitions and control over polariton behavior.
Main Methods:
- Fabrication of a graphene grating on α-MoO3 substrate.
- Engineering the interplay between material anisotropy and synthetic anisotropy.
- Utilizing electrical doping for dynamic tuning of polariton states.
- Experimental validation using scanning near-field optical microscopy (s-SNOM).
Main Results:
- Demonstrated a doping-driven re-entrant topological transition (Hyperbolic-Elliptic-Hyperbolic).
- Showcased geometric control over the number of topological transitions via grating fill factor.
- Experimentally validated tilted, asymmetric polaritons and vortex patterns.
Conclusions:
- The graphene/α-MoO3 heterostructure provides a versatile platform for programming polaritonic topology, directionality, and symmetry.
- This approach paves the way for advanced reconfigurable nanophotonic devices.
Related Concept Videos
01:10α-Alkylation of Ketones via Enolate Ions
3.8K
Ketones with α protons are deprotonated by strong bases like lithium diisopropylamide (LDA) to form enolate ions. The anion is stabilized by resonance, and its hybrid structure exhibits negative charges on the carbonyl oxygen and the α carbon. This ambident nucleophile can attack an electrophile via two possible sites: the carbonyl oxygen, known as O-attack, or the α carbon, known as C-attack. The nucleophilic attack via the carbanionic site is preferred. This is due to the...
3.8K
01:10Factors Affecting α-Alkylation of Ketones: Choice of Base
3.6K
α-Alkylation of ketones is achieved in the presence of alkyl halides and a base. The reaction proceeds via the formation of an enolate ion followed by nucleophilic substitution. The choice of base employed is essential as it is the key factor in determining the reaction outcome.
The reaction involving bases like EtO− whose conjugate acid EtOH (pKa = 15.9) is stronger than the ketone (pKa = 19.2) results in an equilibrium mixture with higher ketone concentration. As a consequence,...
The reaction involving bases like EtO− whose conjugate acid EtOH (pKa = 15.9) is stronger than the ketone (pKa = 19.2) results in an equilibrium mixture with higher ketone concentration. As a consequence,...
3.6K
01:19Oral Hypoglycemic Agents: α-Glucosidase Inhibitors
568
α-glucosidase inhibitors, including acarbose (Precose), miglitol (Glyset), and voglibose (Voglib) (primarily available in Asia), are drugs that control blood sugar levels by delaying the digestion of starch and disaccharides. They achieve this by inhibiting α-glucosidase enzymes in the intestine, which slow the absorption of carbohydrates in the intestine, which in turn leads to a prolonged release of the glucoregulatory hormone GLP-1 from intestinal L-cells.
Acarbose and miglitol are...
Acarbose and miglitol are...
568
01:21Acid-Catalyzed α-Halogenation of Aldehydes and Ketones
4.9K
By replacing an α-hydrogen with a halogen, acid-catalyzed α-halogenation of aldehydes or ketones yields a monohalogenated product
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
4.9K
00:51Base-Promoted α-Halogenation of Aldehydes and Ketones
4.2K
α-Halogenation of aldehydes and ketones is a reaction involving the substitution of α hydrogens with halogens in the presence of a base. The reaction begins with the abstraction of α hydrogen by the base to produce a nucleophilic enolate ion. This intermediate undergoes a subsequent nucleophilic substitution with the halogen to produce a monohalogenated carbonyl compound. If the starting substrate has more than one α hydrogen, it is difficult to stop the reaction...
4.2K
01:17Reactions of α-Halocarbonyl Compounds: Nucleophilic Substitution
3.9K
Nucleophilic substitution in α-halocarbonyl compounds can be achieved via an SN2 pathway. The reaction in α-haloketones is generally carried out with less basic nucleophiles. The use of strong basic nucleophiles leads to the generation of α-haloenolate ions, which often participate in other side reactions.
3.9K