Shivakumar Jolad

Testing the topological nature of the fractional quantum Hall edge.

We carry out numerical diagonalization for much larger systems than before by restricting the fractional quantum Hall (FQH) edge excitations to a basis that is exact for a short-range interaction and very accurate for the Coulomb interaction. This enables us to perform substantial tests of the predicted universality of the edge physics. Our results suggest the possibility that the behavior of the FQH edge is intrinsically nonuniversal, even in the absence of edge reconstruction, and therefore may not bear a sharp and unique relation to the nature of the bulk FQH state.

Fractional quantum Hall edge: Effect of nonlinear dispersion and edge roton

According to Wens theory, a universal behavior of the fractional quantum Hall edge is expected at sufficiently low energies, where the dispersion of the elementary edge excitation is linear. A microscopic calculation shows that the actual dispersion is indeed linear at low energies, but deviates from linearity beyond certain energy, and also exhibits an edge roton minimum. We determine the edge exponent from a microscopic approach, and find that the nonlinearity of the dispersion makes a surprisingly small correction to the edge exponent even at energies higher than the roton energy. We explain this insensitivity as arising from the fact that the energy at maximum spectral weight continues to show an almost linear behavior up to fairly high energies. We also study, in an effective-field theory, how interactions modify the exponent for a reconstructed edge with multiple edge modes. Relevance to experiment is discussed.

Electron operator at the edge of the 1 ∕ 3 fractional quantum Hall liquid

This study builds upon the work of Palacios and MacDonald [Phys. Rev. Lett. 76, 118 (1996)], wherein they identify the bosonic excitations of Wens approach for the edge of the

Microscopic study of the 2/5 fractional quantum Hall edge

1∕3

Phase diagram for bilayer quantum Hall effect at total filling nuT=5

fractional quantum Hall state with certain operators introduced by Stone. Using a quantum Monte Carlo method, we extend this approach to larger systems containing up to 40 electrons and obtain more accurate thermodynamic limits for various matrix elements for a short-range interaction. The results are in agreement with those of Palacios and MacDonald for small systems, but offer further insight into a detailed approach to the thermodynamic limit. For the short range interaction, the results are consistent with chiral Luttinger liquid predictions. We also study excitations using the Coulomb ground state for up to nine electrons to ascertain the effect of interactions on the results; in this case, our tests of the chiral Luttinger liquid approach are inconclusive.

Measuring diversity and coherence using hierarchical APS-PACS classification of sub fields of physics and their impact on citations.

This paper reports on our study of the edge of the 2/5 fractional quantum Hall state, which is more complicated than the edge of the 1/3 state because of the presence of edge sectors corresponding to different partitions of composite fermions in the lowest two Lambda levels. The addition of an electron at the edge is a nonperturbative process and it is not a priori obvious in what manner the added electron distributes itself over these sectors. We show, from a microscopic calculation, that when an electron is added at the edge of the ground state in the [N(1), N(2)] sector, where N(1) and N(2) are the numbers of composite fermions in the lowest two Lambda levels, the resulting state lies in either [N(1) + 1, N(2)] or [N(1), N(2) + 1] sectors; adding an electron at the edge is thus equivalent to adding a composite fermion at the edge. The coupling to other sectors of the form [N(1) + 1 + k, N(2) - k], k integer, is negligible in the asymptotically low-energy limit. This study also allows a detailed comparison with the two-boson model of the 2/5 edge. We compute the spectral weights and find that while the individual spectral weights are complicated and nonuniversal, their sum is consistent with an effective two-boson description of the 2/5 edge.