Helical liquids and Majorana bound states in quantum wires

Helical liquids and Majorana bound states in quantum wires

10 Jun 2010 | Yuval Oreg, Gil Refael, and Felix von Oppen
This paper explores the formation of helical liquids and Majorana bound states in quantum wires. The authors show that when spin-orbit coupling is combined with a Zeeman field or strong interactions, a helical liquid can form in single-channel quantum wires. In such a liquid, electrons with opposite velocities have opposite spin precessions. The presence of a conventional s-wave superconductor in proximity to the wire can lead to the formation of zero-energy Majorana bound states, which are robust against local decoherence and can be used for fault-tolerant quantum memory. Majorana bound states are of great interest in quantum computation due to their non-Abelian statistics, which allows for topological quantum information processing through braiding operations. The paper discusses various physical systems that can host Majorana states, including fractional quantum Hall states, p-wave superconductors, and helical edge modes of topological insulators. However, these systems are experimentally challenging to realize. The authors propose that quantum wires with strong spin-orbit coupling, such as InAs or InSb wires, and banded carbon nanotubes, can form a helical liquid similar to the edges of a topological insulator. These wires can support Majorana states when in proximity to s-wave superconductors and magnetic fields. The authors explain how these states can be created and manipulated by varying the chemical potential, which can be achieved using micron-sized gates. The paper presents a detailed analysis of the Hamiltonian for a spin-orbit coupled quantum wire, showing how the energy spectrum depends on the magnetic field, superconducting gap, and chemical potential. The zero-momentum gap, $ E_0 $, is crucial for the formation of Majorana states. The authors demonstrate that Majorana states can form when these parameters vary spatially or when the chemical potential is tuned. The paper also discusses experimental realizations of Majorana states, including tunneling experiments and Josephson junctions. The authors show that by tuning the superconducting gap, spin gap, or chemical potential, Majorana states can be created and detected. The unique properties of Majorana states, such as their non-Abelian statistics, make them promising for quantum information processing. The paper concludes by emphasizing the potential of these systems for future quantum computing applications.This paper explores the formation of helical liquids and Majorana bound states in quantum wires. The authors show that when spin-orbit coupling is combined with a Zeeman field or strong interactions, a helical liquid can form in single-channel quantum wires. In such a liquid, electrons with opposite velocities have opposite spin precessions. The presence of a conventional s-wave superconductor in proximity to the wire can lead to the formation of zero-energy Majorana bound states, which are robust against local decoherence and can be used for fault-tolerant quantum memory. Majorana bound states are of great interest in quantum computation due to their non-Abelian statistics, which allows for topological quantum information processing through braiding operations. The paper discusses various physical systems that can host Majorana states, including fractional quantum Hall states, p-wave superconductors, and helical edge modes of topological insulators. However, these systems are experimentally challenging to realize. The authors propose that quantum wires with strong spin-orbit coupling, such as InAs or InSb wires, and banded carbon nanotubes, can form a helical liquid similar to the edges of a topological insulator. These wires can support Majorana states when in proximity to s-wave superconductors and magnetic fields. The authors explain how these states can be created and manipulated by varying the chemical potential, which can be achieved using micron-sized gates. The paper presents a detailed analysis of the Hamiltonian for a spin-orbit coupled quantum wire, showing how the energy spectrum depends on the magnetic field, superconducting gap, and chemical potential. The zero-momentum gap, $ E_0 $, is crucial for the formation of Majorana states. The authors demonstrate that Majorana states can form when these parameters vary spatially or when the chemical potential is tuned. The paper also discusses experimental realizations of Majorana states, including tunneling experiments and Josephson junctions. The authors show that by tuning the superconducting gap, spin gap, or chemical potential, Majorana states can be created and detected. The unique properties of Majorana states, such as their non-Abelian statistics, make them promising for quantum information processing. The paper concludes by emphasizing the potential of these systems for future quantum computing applications.
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