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A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
Published on: September 5, 2019
Spin order in paired quantum Hall states.
Ivailo Dimov1, Bertrand I Halperin, Chetan Nayak
1Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547, USA.
Physical Review Letters
|June 4, 2008
Summary
We found that quantum Hall states at 5/2 exhibit spontaneous ferromagnetism. This suggests that even weak ferromagnetic fluctuations can lead to polarized superconducting states in these systems.
Area of Science:
- Condensed Matter Physics
- Quantum Mechanics
- Materials Science
Background:
- Quantum Hall states are exotic states of matter observed in 2D electron systems under strong magnetic fields.
- Even-denominator filling fractions, particularly at nu=5/2, are predicted to host non-Abelian anyonic excitations, crucial for topological quantum computing.
- Understanding the ground state properties, including spin ordering, is vital for realizing these exotic states.
Purpose of the Study:
- To investigate the spin ordering in paired quantum Hall states at even-denominator filling fractions, focusing on nu=5/2.
- To explore the interplay between spin ordering and pairing in these systems.
- To provide theoretical and numerical evidence for the ground state properties of the nu=5/2 quantum Hall state.
Main Methods:
- Numerical simulations to provide evidence for spontaneous ferromagnetism at nu=5/2.
- Development of a Ginzburg-Landau (GL) theory for the spin degrees of freedom in paired Hall states, modeled as a perturbed CP2 model.
- Application of BCS Stoner mean-field theory to compute coefficients in the GL theory for coexisting order parameters.
Main Results:
- Numerical evidence indicates spontaneous ferromagnetism in the incompressible ground state at nu=5/2.
- The Ginzburg-Landau theory for spin degrees of freedom is identified as a perturbed CP2 model.
- Ferromagnetic fluctuations can induce partially or fully polarized superconducting states, even when repulsion is below the Stoner instability threshold.
Conclusions:
- The nu=5/2 quantum Hall state is predicted to exhibit spontaneous ferromagnetism.
- The Ginzburg-Landau theory provides a framework for understanding spin ordering in paired Hall states.
- Ferromagnetic fluctuations play a significant role in determining the polarization of superconducting states in these systems.
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