Gauge fields from strain in graphene

Abstract

We revise the tight binding approach to strained or curved graphene in the presence of external probes such as Photoemission or Scanning Tunneling Microscopy experiments. We show that extra terms arise in the continuum limit of the tight binding Hamiltonian which can not be accounted for by changes in the hopping parameters due to lattice deformations, encoded in the parameter \beta. These material independent extra couplings are of the same order of magnitude as the standard ones and have a geometric origin. They include corrections to the position-dependent Fermi velocity and to a new vector field. We show that the new vector field does not couple to electrons like a standard gauge field and that no ? \beta-independent pseudomagnetic fields exist in strained graphene.Comment: Revised version as publishe

Understanding electron behavior in strained graphene as a reciprocal space distortion

“…As we will see, this mapping and the fact that f (k * ) is equal to its undistorted counterpart lead to pure geometrical effects that only very recently have been identified. [18][19][20][21][22] The other terms depend on the same distortion, but contain hopping corrections. These terms are explicitly detailed in the Appendix A. f ǫ (k * ) contains the modification of the spectrum due to first order in β, while f ǫ 2 (k * ) is the second order correction in β.…”

“…18 The possible physical relevance of the extra β−independent term, predicted in the work of Kitt et al, was discussed by de Juan et al within the TB approach. 19 They also obtained an extra β−independent pseudovector potential but with zero curl. Therefore, they concluded that in strained graphene no β−independent pseudomagnetic field exist.…”

“…16,17 In recent works, the standard description of the straininduced vector field has been supplemented with the explicit inclusion of the local deformation of the lattice vectors. [18][19][20][21][22] After accounting for the actual atomic positions to the TB Hamiltonian, Kitt et al proposed an extra pseudovector potential which is β−independent and different at each of the strained Dirac points. 18 The possible physical relevance of the extra β−independent term, predicted in the work of Kitt et al, was discussed by de Juan et al within the TB approach.…”

Analytic approach to magneto-strain tuning of electronic transport through a graphene nanobubble: perspectives for a strain sensor

“…Conductance experiments have shown the emergence of pseudo-relativistic Landau levels in the presence of strain solely, thus suggesting that the magnitude of the associated pseudo-magnetic fields can reach over 100 Tesla for a small nano-bubble [18,19] or ridge [20] in graphene. From the theoretical perspective, strain-induced gauge fields have been incorporated into extended Dirac Hamiltonians that involve the simultaneous description of both non-equivalent Dirac cones [10,14,16,17,21,22]. Other physical effects, such as charge density waves, can also be included in the form of generalized SU(2) gauge fields [22].…”

“…Perhaps an even more interesting feature arises under the presence of mechanical strain. Within the Dirac approximation, strain enters as a gauge field whose curl represents a pseudo-magnetic field that reverses sign at each Dirac point, thus breaking the valley symmetry [10][11][12][13][14][15][16][17]. Conductance experiments have shown the emergence of pseudo-relativistic Landau levels in the presence of strain solely, thus suggesting that the magnitude of the associated pseudo-magnetic fields can reach over 100 Tesla for a small nano-bubble [18,19] or ridge [20] in graphene.…”