Dirac to Weyl Semimetal Phase Transition via Thickness Control
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Solution Overview
Problem
Current research on phase transitioning from Dirac semimetals to Weyl semimetals faces limitations in stability, particularly under low temperatures or strong magnetic fields.
Innovation Solution
A method involving the formation of Dirac semimetals with specific bismuth-antimony, sodium-bismuth, or cadmium-arsenic compositions on a gallium arsenic substrate to a thickness of 2 nm to 10 nm through molecular beam epitaxy, with a cadmium telluride buffer and capping layers, to induce a stable phase transition to a Weyl semimetal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phase transition from Dirac semimetal to Weyl semimetal is induced under low temperatures or strong magnetic fields, then the phase transition can be achieved, but the stability of the phase transition is poor
Solution Approach 1:
The patent changes the thickness parameter of the Dirac semimetal film from bulk (3D) to thin film (2-10 nm) scale. This parameter change fundamentally alters the electronic structure and stabilizes the Weyl semimetal phase at room temperature, eliminating the need for low temperature or strong magnetic field conditions while achieving stable phase transition.
Solution Approach 2:
The patent transitions from three-dimensional Dirac semimetal to two-dimensional Weyl semimetal by reducing the thickness to 2-10 nm. This dimensional reduction (3D to 2D) changes the electronic band structure and stabilizes the Weyl phase, allowing room temperature operation and improving phase transition stability.
2Reliability
If the thickness of Dirac semimetal is reduced to 2 nm to 10 nm, then the phase transition to Weyl semimetal is stabilized, but the manufacturing precision requirements increase
Solution Approach 1:
The patent introduces a CdTe buffer layer as an intermediary between the substrate and the Dirac semimetal film. This buffer layer serves multiple functions: it provides a suitable crystal structure template, controls the thickness of the subsequent film, and facilitates the growth of high-quality thin films with precise thickness control, thereby enabling stable Weyl phase transition.
Solution Approach 2:
The patent employs molecular beam epitaxy (MBE) to replace conventional fabrication methods. MBE allows atomic-layer precision control of film thickness through controlled deposition rates and timing, enabling precise control of the 2-10 nm thickness range required for stable Weyl phase transition.
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 allows for a stable and controlled phase transition from Dirac to Weyl semimetal, optimizing thickness-dependent characteristics, enhancing the stability and properties of the resulting Weyl semimetal.
Implementation Method 1
forming a Dirac semimetal having a thickness of 2 nm to 10 nm on the cadmium telluride (CdTe) buffer layer by annealing a mixture of bismuth element (Bi) and antimony element (Sb)
Implementation Method 2
by annealing a mixture of bismuth element (Bi) and antimony element (Sb) at a temperature of 250° C. to 350° C.
Implementation Method 3
a phase transition from the Dirac semimetal to a Weyl semimetal (WSM) is induced, wherein the Dirac semimetal is any one semimetal of a bismuth-antimony-based semimetal
Data Source
AI summary
The present disclosure relates to a method of phase-transitioning a three-dimensional Dirac semimetal into a two-dimensional Weyl semimetal and a semimetal that undergoes a phase transition by the same. The Dirac semimetal according to one embodiment may be any one semimetal of a bismuth-antimony-based semimetal, a sodium-bismuth-based semimetal, and a cadmium-arsenic-based semimetal, and may be formed on a substrate to have a thickness of 2 nm to 10 nm so that a phase transition to a Weyl semimetal is induced.