| 1. |
- Azimi Mousolou, Vahid, et al.
(författare)
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Hierarchy of magnon mode entanglement in antiferromagnets
- 2020
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 102:22
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Tidskriftsartikel (refereegranskat)abstract
- Continuous variable entanglement between magnon modes in Heisenberg antiferromagnets with Dzyaloshinskii-Moriya (DM) interaction is examined. Different bosonic modes are identified, which allows us to establish a hierarchy of magnon entanglement. We argue that entanglement between magnon modes is determined by a simple lattice-specific parameter, together with the ratio of the strengths of the DM and Heisenberg exchange interactions, and that magnon entanglement can be detected by means of quantum homodyne techniques. As an illustration of the relevance of our findings for possible entanglement experiments in the solid state, a typical antiferromagnet with the perovskite crystal structure is considered, and it is shown that long wave length magnon modes have a maximal degree of entanglement.
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| 2. |
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| 3. |
- Hofmann, Johannes, 1988, et al.
(författare)
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Anomalously long lifetimes in two-dimensional Fermi liquids
- 2023
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 108:12
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Tidskriftsartikel (refereegranskat)abstract
- A precise characterization of the recently discovered crossover to hydrodynamic transport in electron liquids, and in particular of a conjectured exotic odd-parity transport regime, requires a full solution of the Fermi-liquid collision integral at all temperatures beyond state-of-the-art analytic leading-logarithmic approximations. We develop a general basis expansion of the linearized collision integral applicable at all temperatures, and employ this to determine the decay rates of Fermi surface perturbations in two-dimensional electron liquids. In particular, we provide exhaustive data on the decay rates for a new odd-parity regime, in which parity-even Fermi surface deformations decay rapidly but odd-parity modes are anomalously longlived. We find that this transport regime exists at fairly large temperatures T≲0.1TF, putting this regime within the reach of current experiments.
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| 4. |
- Hofmann, Johannes, 1988, et al.
(författare)
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Collective modes in interacting two-dimensional tomographic Fermi liquids
- 2022
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Ingår i: Physical Review B Condensed Matter. - 0163-1829. ; 106
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Tidskriftsartikel (refereegranskat)abstract
- We develop an analytically solvable model for interacting two-dimensional Fermi liquids with separate collisional relaxation rates for parity-odd and parity-even Fermi surface deformations. Such a disparity of collisional lifetimes exists whenever scattering is restricted to inversion-symmetric Fermi surfaces, and should thus be a generic feature of two-dimensional Fermi liquids. It implies an additional unanticipated "tomographic" transport regime (in between the standard collisionless and hydrodynamic regimes) in which even-parity modes are overdamped while odd-parity modes are collisionless. We derive expressions for both the longitudinal and the transverse conductivity and discuss the collective mode spectrum along the collisionless-tomographic-hydrodynamic crossover. Longitudinal modes cross over from zero sound in the collisionless regime to hydrodynamic first sound in the tomographic and hydrodynamic regime, where odd-parity damping appears as a subleading correction to the lifetime. In charged Fermi liquids with long-range Coulomb coupling, these modes reduce to plasmons with a strongly suppressed odd-parity correction to the damping. The transverse response, by contrast, has a specific tomographic transport regime with two imaginary odd-parity modes, one of which requires a finite repulsive interaction, distinct from both the shear sound in the collisionless regime and an overdamped diffusive current mode in the hydrodynamic limit. Our work demonstrates that there are deep many-body aspects of interacting Fermi liquids, which are often thought to be well-understood theoretically, remaining unexplored.
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| 5. |
- Hofmann, Johannes, 1988
(författare)
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Electromagnetic response of composite Dirac fermions in the half-filled Landau level
- 2021
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Ingår i: Physical Review B Condensed Matter. - 0163-1829. ; 104
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Tidskriftsartikel (refereegranskat)abstract
- An effective field theory of composite Dirac fermions was proposed by Son [Phys. Rev. X 5, 031027 (2015)] as a theory of the half-filled Landau level with explicit particle-hole symmetry. We compute the electromagnetic response of this Son-Dirac theory on the level of the random phase approximation (RPA), where we pay particular attention to the effect of an additional composite-fermion dipole term that is needed to restore Galilean invariance. We find that once this dipole correction is taken into account, spurious interband transitions and collective modes that are present in the response of the unmodified theory either cancel or are strongly suppressed. We demonstrate that this gives rise to a consistent theory of the half-filled Landau level valid at all frequencies, at least to leading order in the momentum. In addition, the dipole contribution modifies the Fermi-liquid response at small frequency and momentum, which is a prediction of the Son-Dirac theory within the RPA that distinguishes it from a separate description of the half-filled Landau level by Halperin, Lee, and Read within the RPA.
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