Designing flat bands by strain

Bi, Zhen; Yuan, Noah F. Q.; Fu, Liang

doi:10.1103/physrevb.100.035448

Cited by 196 publications

(213 citation statements)

References 49 publications

(70 reference statements)

Supporting

Mentioning

198

Contrasting

Unclassified

Order By: Relevance

“…TMD monolayers have their spin-valley locked conduction and valence band edges at the ± corners of Brillouin zone, which are described by the massive Dirac model (24). We focus here on the physics at these band edges in a homobilayer moiré, formed by a small twisting or strain applied to one layer in R-stacking (25) (c.f. Fig.…”

Section: Resultsmentioning

confidence: 99%

Giant magnetic field from moiré induced Berry phase in homobilayer semiconductors

Chen

Yao

2019

National Science Review

View full text Add to dashboard Cite

When quasiparticles move in condensed matters, the texture of their internal quantum structure as a function of position and momentum can give rise to Berry phases that have profound effects on the material's properties. Seminal examples include the anomalous Hall and spin Hall effects from the momentum-space Berry phases in homogeneous crystals. Here, we explore a conjugate form of electron Berry phase arising from the moiré pattern: the texture of atomic configurations in real space. In homobilayer transition metal dichalcogenides, we show the real-space Berry phase from moiré patterns manifests as a periodic magnetic field with magnitudes up to hundreds of Tesla. This quantity distinguishes moiré patterns from different origins, which can have identical potential landscape but opposite quantized magnetic flux per supercell. For low energy carriers, the homobilayer moirés realize topological flux lattices for the quantum spin Hall effect. An interlayer bias can continuously tune the spatial profile of moiré magnetic field, whereas the flux per supercell is a topological quantity that can only have a quantized jump observable at moderate bias. We also reveal the important role of the non-Abelian Berry phase in shaping the energy landscape in small moiré patterns. Our work points to new possibilities to access ultra-high magnetic fields that can be tailored on the nanoscale by electrical and mechanical controls.

show abstract

Section: Resultsmentioning

confidence: 99%

Giant magnetic field from moiré induced Berry phase in homobilayer semiconductors

Chen

Yao

2019

National Science Review

View full text Add to dashboard Cite

show abstract

“…We modified the continuum model as described in ref. 8 to include the effect of strain. The influence of relaxation is incorporated by estimating the area ratio of AA and AB regions, which translates to the ratio of uAA/uAB as described in ref.…”

Section: Extended Continuum Modelmentioning

confidence: 99%

Spectroscopic signatures of many-body correlations in magic-angle twisted bilayer graphene

Xie

Lian

Jäck

et al. 2019

Nature

626

503

View full text Add to dashboard Cite

The discovery of superconducting and insulating states in magic angle twisted bilayer graphene (MATBG) 1,2 has ignited considerable interest in understanding the nature of electronic interactions in this chemically pristine material system. The phenomenological similarity of the MATBG transport properties as a functionof doping with those of the high-Tc cuprates and other unconventional superconductors 1,2,3 suggests the possibility that MATBG may be a highly interacting system. However, there have not been any direct experimental evidence for strong many-body correlations in MATBG. Here we provide such evidence from using high-resolution spectroscopic measurements, as a function of carrier density, with a scanning tunneling microscopy (STM). We find MATBG to display unusual spectroscopic characteristics that can be attributed to electron-electron interactions over a wide range of doping, including when superconductivity emerges in this system. We show that our measurements cannot be explained with a mean-field approach for modeling electron-electron interaction in MATBG. The breakdown of a mean-field approach for understanding the properties of other correlated superconductors, such as cuprates, has long inspired the study of highly correlated Hubbard model 3 . We experimental effort has come from NSF-MRSEC programs through the Princeton

show abstract

“…Details of continuum model can be found in the Supplemental Material. We may include more ingredients such as lattice relaxation [32,59] and strain [60] to better describe TBG, thus the Fermi surface topology will depend on more details of the model. Nevertheless, the existence of high-order VHS and critical twist angle θ c is robust [60].…”

mentioning

confidence: 99%

Magic of high-order van Hove singularity

Yuan¹,

Isobe²,

Fu³

2019

Nat Commun

Self Cite

152

153

View full text Add to dashboard Cite

The van Hove singularity in density of states generally exists in periodic systems due to the presence of saddle points of energy dispersion in momentum space. We introduce a new type of van Hove singularity in two dimensions, resulting from high-order saddle points and exhibiting power-law divergent density of states. We show that high-order van Hove singularity can be generally achieved by tuning the band structure with a single parameter in moiré superlattices, such as twisted bilayer graphene by tuning twist angle or applying pressure, and trilayer graphene by applying vertical electric field. Correlation effects from high-order van Hove singularity near Fermi level are also discussed.

show abstract

Designing flat bands by strain

Cited by 196 publications

References 49 publications

Giant magnetic field from moiré induced Berry phase in homobilayer semiconductors

Giant magnetic field from moiré induced Berry phase in homobilayer semiconductors

Spectroscopic signatures of many-body correlations in magic-angle twisted bilayer graphene

Magic of high-order van Hove singularity

Contact Info

Product

Resources

About