Boundary effects on the local density of states of one-dimensional Mott insulators and charge density wave states

Abstract

We determine the local density of states (LDOS) for spin-gapped one-dimensional charge density wave (CDW) states and Mott insulators in the presence of a hard-wall boundary. We calculate the boundary contribution to the single-particle Green function in the low-energy limit using field theory techniques and analyze it in terms of its Fourier transform in both time and space. The boundary LDOS in the CDW case exhibits a singularity at momentum 2kF, which is indicative of the pinning of the CDW order at the impurity. We further observe several dispersing features at frequencies above the spin gap, which provide a characteristic signature of spin-charge separation. This demonstrates that the boundary LDOS can be used to infer properties of the underlying bulk system. In presence of a boundary magnetic field mid-gap states localized at the boundary emerge. We investigate the signature of such bound states in the LDOS. We discuss implications of our results on STM experiments on quasi-1D systems such as two-leg ladder materials like Sr14Cu24O41. By exchanging the roles of charge and spin sectors, all our results directly carry over to the case of one-dimensional Mott insulators.

Theory of interacting topological crystalline insulators

“…As a result, there appears a gap in the flavor sector, while the charge sector remains gapless and fluctuates. Boundaries and impurities affect the charge mode by pinning a fluctuating charge density wave, which can be detected by scanning tunneling microscope measurement similar to the case of Luther-Emery liquid with a spin gap [42].…”

Boundary Resonances inS=1/2Antiferromagnetic Chains Under a Staggered Field

“…The low-energy effective theory of the system is the quantum sine Gordon field theory with boundaries. In fact, this theory is integrable even in the presence of a boundary, and boundary bound states (BBS) of elementary excitations have been found in the exact solution [9][10][11][12][13][14]. The existence of BBS, and modification of the selection rules, imply extra resonances in addition to those in the bulk.…”

Quasiparticle Scattering off Defects and Possible Bound States in Charge-Ordered YBa2Cu3OyZhou1, Hirata2, Wu3 et al. 2017Phys. Rev. Lett.111331View full textAdd to dashboardCite

“…A natural question is whether the effect is sensitive to the uniaxial nature of the modulation in high fields [2,13] or to a possible d-wave symmetry of the intra-unit-cell form factor [59,60] in high fields. Theoretically, bound states have been found, under certain conditions, in models of one-dimensional CDW [61,62] and in the d-density-wave state [63][64][65][66][67][68], but they do not occur at E F (note that they only need to have a finite weight at E F to contribute to the Knight shift). Also, the possible presence of a Dirac cone in the band structure could provide clues on the reconstructed Fermi-surface in high fields.…”