Emergent momentum scale, localization, and van Hove singularities in the graphene twist bilayer

2013 ◽  
Vol 87 (24) ◽  
Author(s):  
S. Shallcross ◽  
S. Sharma ◽  
O. Pankratov
2020 ◽  
Vol 6 (1) ◽  
Author(s):  
M. Umar Farooq ◽  
Arqum Hashmi ◽  
Tomoya Ono ◽  
Li Huang

AbstractUsing first-principles calculations, we investigate the possibility of realizing valley Hall effects (VHE) in blistered graphene sheets. We show that the Van Hove singularities (VHS) induced by structural deformations can give rise to interesting spin–valley Hall phenomena. The broken degeneracy of spin degree of freedom results in spin-filtered VH states and the valley conductivity have a Hall plateau of ±e2/2h, while the blistered structures with time-reversal symmetry show the VHE with the opposite sign of $$\sigma _{xy}^{K/K^{\prime}}$$ σ x y K / K ′ (e2/2h) in the two valleys. Remarkably, these results show that the distinguishable chiral valley pseudospin state can occur even in the presence of VHS induced spin splitting. The robust chiral spin–momentum textures in both massless and massive Dirac cones of the blistered systems indicate significant suppression of carrier back-scattering. Our study provides a different approach to realize spin-filtered and spin-valley contrasting Hall effects in graphene-based devices without any external field.


2001 ◽  
Vol 706 ◽  
Author(s):  
A. G. Souza Filho ◽  
A. Joribo ◽  
G. Dresselhaus ◽  
M. S. Dresselhaus ◽  
A. K. Swan ◽  
...  

AbstractWe analyze the dependence of the second-order G'-band profile in terms of their (n,m) indices by measuring the resonance Raman spectra of several semiconducting and metalic isolated single wal carbon nanotubes. We show that this profile is very sensitive to the electronic structure, thus making it possible to get structural (n,m) information and to probe the splitting of the van Hove singularities in the electronic density of states due to the trigona warping effect.


2013 ◽  
Vol 28 (35) ◽  
pp. 1350161 ◽  
Author(s):  
SUNANDAN GANGOPADHYAY ◽  
ANIRBAN SAHA ◽  
SWARUP SAHA

Interaction of linearized gravitational waves with a otherwise free particle has been studied quantum mechanically in a noncommutative (NC) phase-space to examine whether the particle's response to the gravitational wave gets modified due to spatial and/or momentum noncommutativity. The result shows that momentum noncommutativity introduces a oscillatory noise with a specific frequency determined by the fundamental momentum scale and particle mass. Because of the global nature of the phase-space noncommutativity such noise will have similar characteristics for all detector sites and thus will stand out in a data cross-correlation procedure. If detected, this noise will provide evidence of momentum noncommutativity and also an estimation of the relevant noncommutative parameter.


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