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Bilayer graphene coherent states

J C David Fernández, Dennis I. Martínez-Moreno

Published Jul 5, 2020• 0 citations
OpenAlex

Abstract

In this paper we consider the interaction of electrons in bilayer graphene with a constant homogeneous magnetic field which is orthogonal to the bilayer surface. Departing from the energy eigenstates of the effective Hamiltonian, the corresponding coherent states will be constructed. For doing this, first we will determine appropriate creation and annihilation operators in order to subsequently derive the coherent states as eigenstates of the annihilation operator with complex eigenvalue. Then, we will calculate some physical quantities, as the Heisenberg uncertainty relation, the probabilities and current density as well as the mean energy value. Finally, we will explore the time evolution for these states and we will compare it with the corresponding evolution for monolayer graphene coherent states.

Related papers

Bilayer graphene coherent states

David J. Fernández C., Dennis I. Martínez-Moreno

In this paper we consider the interaction of electrons in bilayer graphene with a constant homogeneous magnetic field which is orthogonal to the bilayer surface. Departing from the energy eigenstates of the effective Hamiltonian, the corresponding coherent states will be constructed. For doing this, first we will determine appropriate creation and annihilation operators in order to subsequently derive the coherent states as eigenstates of the annihilation operator with complex eigenvalue. Then, we will calculate some physical quantities, as the Heisenberg uncertainty relation, the probabilities and current density as well as the mean energy value. Finally, we will explore the time evolution for these states and we will compare it with the corresponding evolution for monolayer graphene coherent states.

arXiv:2007.02229•Jul 5, 2020•2 citations

Multiphoton coherent states for bilayer graphene

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Abstract The multiphoton coherent states, a generalization to coherent states, are derived for electrons in bilayer graphene placed in a constant homogeneous magnetic field which is orthogonal to the bilayer surface. For that purpose a generalized annihilation operator is constructed in order to determine the multiphoton coherent states as eigenstates of such operator with complex eigenvalue. In addition, some physical quantities are calculated for these states, as the Heisenberg uncertainty relation, the probability density and the mean energy value. Finally, in order to study the dynamics of the system the time evolution is explored and the time-correlation function is computed.

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Abstract Using exfoliation of graphite, bilayer graphene which is composed of two monolayers of carbon atoms can be obtained. Defining annihilation operator, coherent states for charge carrier of bilayer graphene in a perpendicular magnetic field can be calculated. In this paper, introducing even and odd superposition of bilayer graphene coherent states, we investigate their non-classical properties including entanglement, statistical properties and squeezing. With the use of Concurrence, we have found that these states are entangled and the entanglement goes to zero for large values of coherency parameter. Also, using Mandel parameter and second coherence function, we have realized that only odd states represent sub-Poissonian statistics in some ranges of coherency parameter. In addition, our squeezing considerations show that none of the states exhibits squeezing in quadrature operators. The results of these properties for bilayer graphene coherent states, are different from the similar calculations for monolayer ones.

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In the present thesis, the properties of the entanglement spectra of the ground state of graphene bilayers Bernal-stacked is analytically investigated. In addition, the entanglement spectra of the ground state of the honeycomb lattice in the presence of superconductivity instabilities are analytically studied. We consider not only the eigenvalues of the reduced density matrix that form the entanglement spectrum, but also, its eigenstates. From these eigenstates, we construct topological quantities, such as the Berry phase and the Chern number, in order to investigate the topological properties of the entanglement spectrum. In the first part of this thesis, we present an analytical study of the graphene bilayers, mainly focusing on the effects of the trigonal warping. When the term causing the trigonal warping is neglected, the entanglement Hamiltonian obtained by tracing out one layer shows a proportionality with the energetic Hamiltonian of the remaining monolayer graphene, in the limit of strongly coupled layers. We demonstrate that this proportionality leads to an agreement of the topological quantities of these Hamiltonians. Moreover, we demonstrate that the entanglement spectrum of graphene bilayers with a trigonal warping spectrum clearly differs in the geometric shape from the energy spectrum of the remaining monolayer graphene. However, there is an agreement of the topological quantities such as Berry phase contributions to Chern numbers. In the second part of this thesis, we give a detailed study of graphene in the presence of superconductivity instabilities, mainly considering the s-wave and the chiral dx2−y2 +idxy state.We investigate the relationship between the entanglement and energy spectrum, making use of the concepts of the Chern number constructed from eigenstates of the entanglement Hamiltonian. We demonstrate that the entanglement and remaining subsystem Hamiltonians can have different topologies. These findings are illustrated by considering the entanglement Hamiltonian of the ground state of graphene with dx2−y2 + idxy superconductivity obtained by tracing out one spin direction. Our investigations are based on closed analytical expressions for the full eigensystem in the entire Brillouin zone of bilayer graphene with a trigonally warped spectrum and graphene with superconductivity instabilities.

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Abstract In this paper, we discuss the quantum walk of two interacting particles on graphene structure graph. Based on the localized graphene structure graph, we get three cases for the position of the two particles, that is ∂(i, j) = 0, ∂(i, j) = 1, and ∂(i, j) = 2. Subsequently, we investigate the quantum walk of two interacting particles from a new perspective, namely, based on the view of quantum probability, a localized quantum decomposition was used to get the corresponding creation operators and annihilation operators for the first time. Finally, we get the Hamiltonian and the time evolution operator of two interacting particles on the graphene structure graph.

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In this paper we consider the interaction of electrons in bilayer graphene with a constant homogeneous magnetic field which is orthogonal to the bilayer surface. Departing from the energy eigenstates of the effective Hamiltonian, the corresponding coherent states will be constructed. For doing this, first we will determine appropriate creation and annihilation operators in order to subsequently derive the coherent states as eigenstates of the annihilation operator with complex eigenvalue. Then, we will calculate some physical quantities, as the Heisenberg uncertainty relation, the probabilities and current density as well as the mean energy value. Finally, we will explore the time evolution for these states and we will compare it with the corresponding evolution for monolayer graphene coherent states.
In this paper we consider the interaction of electrons in bilayer graphene with a constant homogeneous magnetic field which is orthogonal to the bilayer surface. Departing from the energy eigenstates of the effective Hamiltonian, the corresponding coherent states will be constructed. For doing this, first we will determine appropriate creation and annihilation operators in order to subsequently derive the coherent states as eigenstates of the annihilation operator with complex eigenvalue. Then, we will calculate some physical quantities, as the Heisenberg uncertainty relation, the probabilities and current density as well as the mean energy value. Finally, we will explore the time evolution for these states and we will compare it with the corresponding evolution for monolayer graphene coherent states.
Abstract The multiphoton coherent states, a generalization to coherent states, are derived for electrons in bilayer graphene placed in a constant homogeneous magnetic field which is orthogonal to the bilayer surface. For that purpose a generalized annihilation operator is constructed in order to determine the multiphoton coherent states as eigenstates of such operator with complex eigenvalue. In addition, some physical quantities are calculated for these states, as the Heisenberg uncertainty relation, the probability density and the mean energy value. Finally, in order to study the dynamics of the system the time evolution is explored and the time-correlation function is computed.
Abstract Using exfoliation of graphite, bilayer graphene which is composed of two monolayers of carbon atoms can be obtained. Defining annihilation operator, coherent states for charge carrier of bilayer graphene in a perpendicular magnetic field can be calculated. In this paper, introducing even and odd superposition of bilayer graphene coherent states, we investigate their non-classical properties including entanglement, statistical properties and squeezing. With the use of Concurrence, we have found that these states are entangled and the entanglement goes to zero for large values of coherency parameter. Also, using Mandel parameter and second coherence function, we have realized that only odd states represent sub-Poissonian statistics in some ranges of coherency parameter. In addition, our squeezing considerations show that none of the states exhibits squeezing in quadrature operators. The results of these properties for bilayer graphene coherent states, are different from the similar calculations for monolayer ones.
In the present thesis, the properties of the entanglement spectra of the ground state of graphene bilayers Bernal-stacked is analytically investigated. In addition, the entanglement spectra of the ground state of the honeycomb lattice in the presence of superconductivity instabilities are analytically studied. We consider not only the eigenvalues of the reduced density matrix that form the entanglement spectrum, but also, its eigenstates. From these eigenstates, we construct topological quantities, such as the Berry phase and the Chern number, in order to investigate the topological properties of the entanglement spectrum. In the first part of this thesis, we present an analytical study of the graphene bilayers, mainly focusing on the effects of the trigonal warping. When the term causing the trigonal warping is neglected, the entanglement Hamiltonian obtained by tracing out one layer shows a proportionality with the energetic Hamiltonian of the remaining monolayer graphene, in the limit of strongly coupled layers. We demonstrate that this proportionality leads to an agreement of the topological quantities of these Hamiltonians. Moreover, we demonstrate that the entanglement spectrum of graphene bilayers with a trigonal warping spectrum clearly differs in the geometric shape from the energy spectrum of the remaining monolayer graphene. However, there is an agreement of the topological quantities such as Berry phase contributions to Chern numbers. In the second part of this thesis, we give a detailed study of graphene in the presence of superconductivity instabilities, mainly considering the s-wave and the chiral dx2−y2 +idxy state.We investigate the relationship between the entanglement and energy spectrum, making use of the concepts of the Chern number constructed from eigenstates of the entanglement Hamiltonian. We demonstrate that the entanglement and remaining subsystem Hamiltonians can have different topologies. These findings are illustrated by considering the entanglement Hamiltonian of the ground state of graphene with dx2−y2 + idxy superconductivity obtained by tracing out one spin direction. Our investigations are based on closed analytical expressions for the full eigensystem in the entire Brillouin zone of bilayer graphene with a trigonally warped spectrum and graphene with superconductivity instabilities.
Abstract In this paper, we discuss the quantum walk of two interacting particles on graphene structure graph. Based on the localized graphene structure graph, we get three cases for the position of the two particles, that is ∂(i, j) = 0, ∂(i, j) = 1, and ∂(i, j) = 2. Subsequently, we investigate the quantum walk of two interacting particles from a new perspective, namely, based on the view of quantum probability, a localized quantum decomposition was used to get the corresponding creation operators and annihilation operators for the first time. Finally, we get the Hamiltonian and the time evolution operator of two interacting particles on the graphene structure graph.