arXiv:cond-mat/0608378 · Physical Review B

Generalized quantum Hall projection Hamiltonians

Steven H. Simon, Edward H. Rezayi, Nigel R. Cooper

Published Feb 12, 2007• 71 citations

Abstract

Certain well known quantum Hall states---including the Laughlin states, the Moore-Read Pfaffian, and the Read-Rezayi Parafermion states---can be defined as the unique lowest degree symmetric analytic function that vanishes as at least $p$ powers as some number $(g+1)$ of particles approach the same point. Analogously, these same quantum Hall states can be generated as the exact highest density zero energy state of simple angular momentum projection operators. Following this theme we determine the highest density zero energy state for many other values of $p$ and $g$.

DOI: 10.1103/physrevb.75.075318

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Quaternate generalization of Pfaffian state at $ν=5/2$

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Tracing non-Abelian anyons via impurity particles

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arXiv:cond-mat/0608378 · Physical Review B

Generalized quantum Hall projection Hamiltonians

Steven H. Simon, Edward H. Rezayi, Nigel R. Cooper

Published Feb 12, 2007• 71 citations

arXiv HTML PDF

Abstract

p

powers as some number

(g+1)

of particles approach the same point. Analogously, these same quantum Hall states can be generated as the exact highest density zero energy state of simple angular momentum projection operators. Following this theme we determine the highest density zero energy state for many other values of

p

and

g

DOI: 10.1103/physrevb.75.075318

Related papers

Model anisotropic quantum Hall states

Ruizhi Qiu, F. D. M. Haldane, Xin Wan +2 more

Model quantum Hall states including Laughlin, Moore-Read, and Read-Rezayi states are generalized into appropriate anisotropic form. The generalized states are exact zero-energy eigenstates of corresponding anisotropic two- or multibody Hamiltonians, and explicitly illustrate the existence of geometric degree of freedom in the fractional quantum Hall effect. These generalized model quantum Hall states can provide a good description of the quantum Hall system with anisotropic interactions. Some numeric results of these anisotropic quantum Hall states are also presented.Model quantum Hall states including Laughlin, Moore-Read, and Read-Rezayi states are generalized into appropriate anisotropic form. The generalized states are exact zero-energy eigenstates of corresponding anisotropic two- or multibody Hamiltonians, and explicitly illustrate the existence of geometric degree of freedom in the fractional quantum Hall effect. These generalized model quantum Hall states can provide a good description of the quantum Hall system with anisotropic interactions. Some numeric results of these anisotropic quantum Hall states are also presented.

arXiv:1201.1983Physical Review BMar 15, 201288 citations

Beyond paired quantum Hall states: Parafermions and incompressible states in the first excited Landau level

N. Read, Edward H. Rezayi

The Pfaffian quantum Hall states, which can be viewed as involving pairing either of spin-polarized electrons or of composite fermions, are generalized by finding the exact ground states of certain Hamiltonians with $k+1$ -body interactions, for all integers $k>~1.$ The remarkably simple wave functions of these states involve clusters of k particles, and are related to correlators of parafermion currents in two-dimensional conformal field theory. The $k=2$ case is the Pfaffian. For $k>~2,$ the quasiparticle excitations of these systems are expected to possess non-Abelian statistics, like those of the Pfaffian. For $k=3,$ these ground states have large overlaps with the ground states of the (two-body) Coulomb-interaction Hamiltonian for electrons in the first excited Landau level at total filling factors $\ensuremath{\nu}=2+3/5,2+2/5.$The Pfaffian quantum Hall states, which can be viewed as involving pairing either of spin-polarized electrons or of composite fermions, are generalized by finding the exact ground states of certain Hamiltonians with $k+1$-body interactions, for all integers $k>~1.$ The remarkably simple wave functions of these states involve clusters of k particles, and are related to correlators of parafermion currents in two-dimensional conformal field theory. The $k=2$ case is the Pfaffian. For $k>~2,$ the quasiparticle excitations of these systems are expected to possess non-Abelian statistics, like those of the Pfaffian. For $k=3,$ these ground states have large overlaps with the ground states of the (two-body) Coulomb-interaction Hamiltonian for electrons in the first excited Landau level at total filling factors $\ensuremath{\nu}=2+3/5,2+2/5.$

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Fractional Quantum Hall Effects

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Quaternate generalization of Pfaffian state at $ν=5/2$ Quaternate generalization of Pfaffian state at $ν=5/2$

Yue Yu

We consider a quaternately generalized Pfaffian QGPf $(\frac{1}{J(z_i,z_j,z_k,z_l)})[J(z_1,...,z_N)]^2$ in which the square of Vandermonde determinant, $[J(z_1,...,z_N)]^2$ , implies the upmost Landau level is half filled. This wave function is the unique highest density zero energy state of a special short range interacting Hamiltonian. One can think this quaternate composite fermion liquid as a competing ground state of Moore-Read (MR) Pfaffian state at $ν=5/2$ . The degeneracy of the quasihole excitations above the QGPf is higher than that of Moore-Read even Read-Rezayi quasiholes. The QGPf is related to a unitary conformal field theory with $Z_2\times Z_2$ parafermions in coset space $SU(3)_2/U(1)^2$ . Because of the level-rank duality between $SU(3)_2$ and $SU(2)_3$ in conformal field theory, these quasiholes above this QGPf state obeying non-abelian anyonic statistics are expected to support the universal quantum computation at $ν=5/2$ as Read-Rezayi quasiholes at $ν=13/5$ . The edge states of QGPf are very different from those of the Pfaffian's.We consider a quaternately generalized Pfaffian QGPf$(\frac{1}{J(z_i,z_j,z_k,z_l)})[J(z_1,...,z_N)]^2$ in which the square of Vandermonde determinant, $[J(z_1,...,z_N)]^2$, implies the upmost Landau level is half filled. This wave function is the unique highest density zero energy state of a special short range interacting Hamiltonian. One can think this quaternate composite fermion liquid as a competing ground state of Moore-Read (MR) Pfaffian state at $ν=5/2$. The degeneracy of the quasihole excitations above the QGPf is higher than that of Moore-Read even Read-Rezayi quasiholes. The QGPf is related to a unitary conformal field theory with $Z_2\times Z_2$ parafermions in coset space $SU(3)_2/U(1)^2$ . Because of the level-rank duality between $SU(3)_2$ and $SU(2)_3$ in conformal field theory, these quasiholes above this QGPf state obeying non-abelian anyonic statistics are expected to support the universal quantum computation at $ν=5/2$ as Read-Rezayi quasiholes at $ν=13/5$. The edge states of QGPf are very different from those of the Pfaffian's.

arXiv:0801.3541Jan 23, 20080 citations

Tracing non-Abelian anyons via impurity particles

Niccolò Baldelli, Bruno Juliá-Díaz, Utso Bhattacharya +2 more

Non-Abelian excitations are an interesting feature of many fractional quantum Hall phases, including those phases described by the Moore-Read (or Pfaffian) wave function. However, the detection of the non-Abelian quasiparticles is challenging. Here, we consider a system described by the Moore-Read wave function and assume that impurity particles bind to its quasiholes. Then, the angular momentum of the impurities, reflected also by the impurity density, provides a useful witness of the physics of the non-Abelian excitations. By demanding that the impurities are constrained to the lowest Landau level, we are able to write down the corresponding many-body wave function describing both the Moore-Read liquid and the impurities. Through Monte Carlo sampling, we determine the impurity angular momentum, and we show that it suggests a quantum-statistical parameter $\ensuremath{\alpha}=a\ensuremath{\nu}\ensuremath{-}b+P/2$ for the quasiholes, where $\ensuremath{\alpha}$ ranges from 0 for bosons to 1 for fermions. A reasonable agreement with the Monte Carlo results is obtained for $a=1/4$ , $b=1/8$ , and $P=0,1$ depending on the parity of the particle number in the Moore-Read liquid. This parity dependence of the angular momentum serves as an unambiguous demonstration of the non-Abelian nature of the excitations. In addition to the studies of excitations in the Moore-Read liquid, we also apply our scheme to Laughlin liquids, for which we focus on interacting bosonic impurities. With this, the impurities themselves form Laughlin states, which allows for a study of hierarchical fractional quantum Hall states.Non-Abelian excitations are an interesting feature of many fractional quantum Hall phases, including those phases described by the Moore-Read (or Pfaffian) wave function. However, the detection of the non-Abelian quasiparticles is challenging. Here, we consider a system described by the Moore-Read wave function and assume that impurity particles bind to its quasiholes. Then, the angular momentum of the impurities, reflected also by the impurity density, provides a useful witness of the physics of the non-Abelian excitations. By demanding that the impurities are constrained to the lowest Landau level, we are able to write down the corresponding many-body wave function describing both the Moore-Read liquid and the impurities. Through Monte Carlo sampling, we determine the impurity angular momentum, and we show that it suggests a quantum-statistical parameter $\ensuremath{\alpha}=a\ensuremath{\nu}\ensuremath{-}b+P/2$ for the quasiholes, where $\ensuremath{\alpha}$ ranges from 0 for bosons to 1 for fermions. A reasonable agreement with the Monte Carlo results is obtained for $a=1/4$, $b=1/8$, and $P=0,1$ depending on the parity of the particle number in the Moore-Read liquid. This parity dependence of the angular momentum serves as an unambiguous demonstration of the non-Abelian nature of the excitations. In addition to the studies of excitations in the Moore-Read liquid, we also apply our scheme to Laughlin liquids, for which we focus on interacting bosonic impurities. With this, the impurities themselves form Laughlin states, which allows for a study of hierarchical fractional quantum Hall states.

arXiv:2102.02072Physical review. B./Physical review. BJul 16, 202121 citations

Energy projection and modified Laughlin states

Mikael Fremling, Jørgen Fulsebakke, Niall Moran +1 more

We develop a method to efficiently calculate trial wave functions for quantum Hall systems which involve projection onto the lowest Landau level. The method essentially replaces the lowest Landau level projection by projection onto the $M$ lowest eigenstates of a suitably chosen Hamiltonian acting within the lowest Landau level. The resulting ``energy projection'' is a controlled approximation to the exact lowest Landau level projection which improves with increasing $M$ . It allows us to study the projected trial wave functions for system sizes close to the maximal sizes that can be reached by exact diagonalization and can be straightforwardly applied in any geometry. As a first application and test case, we study a class of trial wave functions first proposed by Girvin and Jach [Girvin and Jach, Phys. Rev. B 29, 5617 (1984)], which are modifications of the Laughlin states involving a single real parameter. While these modified Laughlin states probably represent the same universality class exemplified by the Laughlin wave functions, we show by extensive numerical work for systems on the sphere and torus that they provide a significant improvement of the variational energy, overlap with the exact wave function and properties of the entanglement spectrum.We develop a method to efficiently calculate trial wave functions for quantum Hall systems which involve projection onto the lowest Landau level. The method essentially replaces the lowest Landau level projection by projection onto the $M$ lowest eigenstates of a suitably chosen Hamiltonian acting within the lowest Landau level. The resulting ``energy projection'' is a controlled approximation to the exact lowest Landau level projection which improves with increasing $M$. It allows us to study the projected trial wave functions for system sizes close to the maximal sizes that can be reached by exact diagonalization and can be straightforwardly applied in any geometry. As a first application and test case, we study a class of trial wave functions first proposed by Girvin and Jach [Girvin and Jach, Phys. Rev. B 29, 5617 (1984)], which are modifications of the Laughlin states involving a single real parameter. While these modified Laughlin states probably represent the same universality class exemplified by the Laughlin wave functions, we show by extensive numerical work for systems on the sphere and torus that they provide a significant improvement of the variational energy, overlap with the exact wave function and properties of the entanglement spectrum.

arXiv:1601.06736Physical review. B./Physical review. BJun 24, 201615 citations

p

powers as some number

(g+1)

p

and

g

k+1

-body interactions, for all integers

k>~1.

The remarkably simple wave functions of these states involve clusters of k particles, and are related to correlators of parafermion currents in two-dimensional conformal field theory. The

k=2

case is the Pfaffian. For

k>~2,

the quasiparticle excitations of these systems are expected to possess non-Abelian statistics, like those of the Pfaffian. For

k=3,

these ground states have large overlaps with the ground states of the (two-body) Coulomb-interaction Hamiltonian for electrons in the first excited Landau level at total filling factors $\ensuremath{\nu}=2+3/5,2+2/5.$

Quaternate generalization of Pfaffian state at

ν=5/2

We consider a quaternately generalized Pfaffian QGPf

(\frac{1}{J(z_i,z_j,z_k,z_l)})[J(z_1,...,z_N)]^2

in which the square of Vandermonde determinant,

[J(z_1,...,z_N)]^2

, implies the upmost Landau level is half filled. This wave function is the unique highest density zero energy state of a special short range interacting Hamiltonian. One can think this quaternate composite fermion liquid as a competing ground state of Moore-Read (MR) Pfaffian state at

ν=5/2

. The degeneracy of the quasihole excitations above the QGPf is higher than that of Moore-Read even Read-Rezayi quasiholes. The QGPf is related to a unitary conformal field theory with

Z_2\times Z_2

parafermions in coset space

SU(3)_2/U(1)^2

. Because of the level-rank duality between

SU(3)_2

and

SU(2)_3

in conformal field theory, these quasiholes above this QGPf state obeying non-abelian anyonic statistics are expected to support the universal quantum computation at

ν=5/2

as Read-Rezayi quasiholes at

ν=13/5

. The edge states of QGPf are very different from those of the Pfaffian's.

a=1/4

b=1/8

, and

P=0,1

depending on the parity of the particle number in the Moore-Read liquid. This parity dependence of the angular momentum serves as an unambiguous demonstration of the non-Abelian nature of the excitations. In addition to the studies of excitations in the Moore-Read liquid, we also apply our scheme to Laughlin liquids, for which we focus on interacting bosonic impurities. With this, the impurities themselves form Laughlin states, which allows for a study of hierarchical fractional quantum Hall states.

M

lowest eigenstates of a suitably chosen Hamiltonian acting within the lowest Landau level. The resulting ``energy projection'' is a controlled approximation to the exact lowest Landau level projection which improves with increasing

M

. It allows us to study the projected trial wave functions for system sizes close to the maximal sizes that can be reached by exact diagonalization and can be straightforwardly applied in any geometry. As a first application and test case, we study a class of trial wave functions first proposed by Girvin and Jach [Girvin and Jach, Phys. Rev. B 29, 5617 (1984)], which are modifications of the Laughlin states involving a single real parameter. While these modified Laughlin states probably represent the same universality class exemplified by the Laughlin wave functions, we show by extensive numerical work for systems on the sphere and torus that they provide a significant improvement of the variational energy, overlap with the exact wave function and properties of the entanglement spectrum.