Semiconductor Ferromagnetic Insulator Heterostructure for Topological Quantum Computing
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Solution Overview
Problem
Existing topological quantum computing devices require an external magnetic field to lift spin degeneracy in semiconductor nanowires, which is inconvenient for practical implementation.
Innovation Solution
A heterostructure comprising a semiconductor and a ferromagnetic insulator, such as InAs and EuS, is used, where the inherent magnetic field of the ferromagnetic insulator induces Majorana zero modes in the semiconductor, eliminating the need for an external magnetic field, and the materials are lattice-matched to prevent dislocations and oxidation, allowing for epitaxial growth without exposing the semiconductor to air.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an external magnetic field is applied to lift spin degeneracy in semiconductor nanowires, then the topological regime can be induced, but the device complexity and fabrication difficulty increase due to requiring external electromagnets
Solution Approach 1:
The patent extracts the magnetic field generation function from an external electromagnet and relocates it to an internal ferromagnetic insulator layer integrated within the nanowire heterostructure. This eliminates the need for external magnetic field application while maintaining the spin degeneracy lifting effect necessary for topological regime induction.
Solution Approach 2:
The ferromagnetic insulator acts as an intermediary that mediates between the semiconductor nanowire and the required magnetic field. Instead of directly applying an external magnetic field, the ferromagnetic insulator generates a localized magnetic field at the interface, enabling spin degeneracy lifting through exchange interaction without requiring external electromagnets.
2Ease of manufacture
If the semiconductor is exposed to air during ferromagnetic insulator deposition, then the deposition process can be simplified, but oxidation occurs at the semiconductor surface causing interface roughness and degrading device performance
Solution Approach 1:
The patent employs an inert atmosphere (vacuum or protective gas environment) during the ferromagnetic insulator deposition process to prevent oxidation of the semiconductor surface. This maintains the cleanliness and flatness of the semiconductor-ferromagnetic insulator interface while still allowing for practical deposition processes.
Solution Approach 2:
The patent performs preliminary surface preparation and deposition of the ferromagnetic insulator in a controlled environment before any potential oxidation can occur. By preparing the semiconductor surface and immediately covering it with the ferromagnetic insulator layer in an inert atmosphere, the interface quality is preserved while enabling subsequent processing steps.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the induction of the topological regime in nanowires without an external magnetic field, reducing fabrication complexities and improving device performance by maintaining coherent lattice matching and avoiding interface roughness and oxidation, thus enhancing the feasibility of topological quantum computing.
Implementation Method 1
The exchange field between the semiconductor and the ferromagnetic insulator cause the split in the energy levels of the electrons in the semiconductor
Implementation Method 2
Lifting the electron spin degeneracies in solid state materials plays a key role in semiconductor spintronics and is believed to be on the critical path for the development of quantum computation, communication and sensing. In topological quantum computing as well, a requirement for obtaining topologically protected states is to lift the spin degeneracy
Implementation Method 3
The materials are lattice-matched to prevent dislocations and oxidation, allowing for epitaxial growth without exposing the semiconductor to air
Data Source
AI summary
A first aspect provides a topological quantum computing device comprising a network of semiconductor-superconductor nanowires, each nanowire comprising a length of semiconductor formed over a substrate and a coating of superconductor formed over at least part of the semiconductor; wherein at least some of the nanowires further comprise a coating of ferromagnetic insulator disposed over at least part of the semiconductor. A second aspect provides a method of fabricating a quantum or spintronic device comprising a heterostructure of semiconductor and ferromagnetic insulator, by: forming a portion of the semiconductor over a substrate in a first vacuum chamber, and growing a coating of the ferromagnetic insulator on the semiconductor by epitaxy in a second vacuum chamber connected to the first vacuum chamber by a vacuum tunnel, wherein the semiconductor comprises InAs and the ferromagnetic insulator comprises EuS.