Theoretical calculations show that twisted double bilayer graphene (TDBG) under a transverse electric field develops a valley Chern number 2 at charge neutrality. Using thermodynamic and thermal activation measurements we report the experimental observation of a universal closing of the charge neutrality gap in the Hofstadter spectrum of TDBG at 1/2 magnetic flux per unit cell, in agreement with theoretical predictions for a valley Chern number 2 gap. Our theoretical analysis of the experimental data shows that the interaction energy, while larger than the flat-band bandwidth in TDBG near 1° does not alter the emergent valley symmetry or the single-particle band topology.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1103/PhysRevLett.133.246401 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Flexible Control of Chiral Superconductivity in Optically Driven Nodal Point Superconductors with Antiferromagnetism.
Phys Rev Lett
December 2024
Institute for Structure and Function and Department of Physics and Chongqing Key Laboratory for Strongly Coupled Physics, Chongqing University, Chongqing 400044, People's Republic of China and Center of Quantum Materials and Devices, Chongqing University, Chongqing 400044, People's Republic of China.
Recent studies have attracted widespread attention on magnet-superconductor hybrid systems with emergent topological superconductivity. Here, we present the Floquet engineering of realistic two-dimensional topological nodal-point superconductors that are composed of antiferromagnetic monolayers in proximity to an s-wave superconductor. We show that Floquet chiral topological superconductivity arises due to light-induced breaking of the effective time-reversal symmetry.
View Article and Find Full Text PDFEmergent Symmetry and Valley Chern Insulator in Twisted Double-Bilayer Graphene.
Phys Rev Lett
December 2024
Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78758, USA.
Theoretical calculations show that twisted double bilayer graphene (TDBG) under a transverse electric field develops a valley Chern number 2 at charge neutrality. Using thermodynamic and thermal activation measurements we report the experimental observation of a universal closing of the charge neutrality gap in the Hofstadter spectrum of TDBG at 1/2 magnetic flux per unit cell, in agreement with theoretical predictions for a valley Chern number 2 gap. Our theoretical analysis of the experimental data shows that the interaction energy, while larger than the flat-band bandwidth in TDBG near 1° does not alter the emergent valley symmetry or the single-particle band topology.
View Article and Find Full Text PDFTheory of Quantum Anomalous Hall Phases in Pentalayer Rhombohedral Graphene Moiré Structures.
Phys Rev Lett
November 2024
Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Article Synopsis
- * These FQAH phases are linked to unique electron interactions that lead to the formation of a Chern-1 band, which isn't present in noninteracting conditions.
- * The study also explores additional multi-layer graphene structures and identifies conditions under which a similar Chern-1 band can occur, potentially allowing for FQAH physics in other configurations.
Quantum Valley Hall Effect without Berry Curvature.
Phys Rev Lett
November 2024
Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea; Center for Theoretical Physics (CTP), Seoul National University, Seoul 08826, Korea; and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea.
The quantum valley Hall effect (QVHE) is characterized by the valley Chern number (VCN) in a way that one-dimensional (1D) chiral metallic states are guaranteed to appear at the domain walls (DW) between two domains with opposite VCN for a given valley. Although in the case of QVHE, the total Berry curvature (BC) of the system is zero, the BC distributed locally around each valley makes the VCN well defined as long as intervalley scattering is negligible. Here, we propose a new type of valley-dependent topological phenomenon that occurs when the BC is strictly zero at each momentum.
View Article and Find Full Text PDFTrion sensing of a zero-field composite Fermi liquid.
Nature
November 2024
Department of Physics, University of Washington, Seattle, WA, USA.
The half-filled lowest Landau level is a fascinating platform for researching interacting topological phases. A celebrated example is the composite Fermi liquid, a non-Fermi liquid formed by composite fermions in strong magnetic fields. Its zero-field counterpart is predicted in a twisted MoTe bilayer (tMoTe)-a recently discovered fractional Chern insulator exhibiting the fractional quantum anomalous Hall effect.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!