トポロジカル・マター ウェイルフェルミオン半金属とトポロジックフェルミ弧の発見
Su-Yang Xu1, Ilya Belopolski2, Nasser Alidoust1
1Laboratory for Topological Quantum Matter and Spectroscopy (B7), Department of Physics, Princeton University, Princeton, NJ 08544, USA. Princeton Center for Complex Materials, Princeton Institute for Science and Technology of Materials, Princeton University, Princeton, NJ 08544, USA.
Science (New York, N.Y.)
|July 18, 2015
まとめ
研究者らはタンタールアルセニド (TaAs) をウェイル半金属として発見し,これは新しい物質の状態である. この発見により,トポロジカルなフェルミ弧とヴェイルのフェルミオンが直接観測され,物理学と材料科学の新たな道が開かれました.
科学分野:
- 凝縮物質物理学
- 材料科学
- トポロジー
背景:
- ウェイル半金属は,物質のトポロジカル状態であり,新興のウェイルフェルミオンを宿している.
- 独特の電子構造は トポロジーによって保護されたフェルミ弧の表面状態を示します
- これらの性質は,高エネルギー粒子物理学で類似しています.
研究 の 目的:
- 実験的にウェイル半金属を発見し,特徴づけること.
- トポロジカルなフェルミ弧の表面状態と物質内のウェイルフェルミオンを直接観測する.
- フェルミ弧のトポロジカルな性質を,その結末をウェイルノードで観察することで確認する.
主な方法:
- タンタルアルセニド (TaAs) の単一結晶の成長
- 電子構造を検出するための光放出スペクトロスコーピー (PES).
- 大量と表面の電子状態の実験観察.
主要な成果:
- タンタールアルセニド (TaAs) をウェイル半金属として実験的に確認した.
- TaAs単一結晶のトポロジカルフェルミ弧表面状態の直接観測
- TaAsのバルク電子構造におけるウェイルフェルミオンコーンとウェイルノードの観測.
結論:
- フェルミ弧は,トポロジック理論と一致して,ウェイルノードで終わることが観察されました.
- ウェイル半金属としてのTaAsの発見は,トポロジカル現象を研究するためのプラットフォームを提供します.
- この研究は,固体物理と粒子物理を,新興のヴェイルのフェルミオンの研究を通して橋渡ししている.
関連する概念動画
01:17Theory of Metallic Conduction
2.0K
The conduction of free electrons inside a conductor is best described by quantum mechanics. However, a classical model makes predictions close to the results of quantum mechanics. It is called the theory of metallic conduction.
In this theory, Newton's second law of motion is used to determine the acceleration of an electron in the presence of an applied electric field. Then, its velocity is expressed via this acceleration.
An electron moves through the crystal, containing positive ions,...
In this theory, Newton's second law of motion is used to determine the acceleration of an electron in the presence of an applied electric field. Then, its velocity is expressed via this acceleration.
An electron moves through the crystal, containing positive ions,...
2.0K
01:31Ferromagnetism
3.6K
Materials like iron, nickel, and cobalt consist of magnetic domains, within which the magnetic dipoles are arranged parallel to each other. The magnetic dipoles are rigidly aligned in the same direction within a domain by quantum mechanical coupling among the atoms. This coupling is so strong that even thermal agitation at room temperature cannot break it. The result is that each domain has a net dipole moment. However, some materials have weaker coupling, and are ferromagnetic at lower...
3.6K
01:18Fermi Level
2.4K
The Fermi-Dirac function is represented by an S-shaped curve indicating the probability of an energy state being occupied by an electron at a given temperature. The Fermi level is the energy level at which there is a fifty percent chance of finding an electron, and it is positioned between the lower-energy valence band and the higher-energy conduction band.
At absolute zero temperature, electrons fill all energy states up to the Fermi level, leaving upper states empty. As the temperature rises,...
At absolute zero temperature, electrons fill all energy states up to the Fermi level, leaving upper states empty. As the temperature rises,...
2.4K
01:12Fermi Level Dynamics
1.0K
The vacuum level denotes the energy threshold required for an electron to escape from a material surface. It is usually positioned above the conduction band of a semiconductor and acts as a benchmark for comparing electron energies within various materials.
Electron affinity in semiconductors refers to the energy gap between the minimum of its conduction band and the vacuum level and it is a critical parameter in determining how easily a semiconductor can accept additional electrons.
The work...
Electron affinity in semiconductors refers to the energy gap between the minimum of its conduction band and the vacuum level and it is a critical parameter in determining how easily a semiconductor can accept additional electrons.
The work...
1.0K
01:24Metal-Semiconductor Junctions
1.4K
The contact of metal and semiconductor can lead to the formation of a junction with either Schottky or Ohmic behavior.
Schottky Barriers
Schottky barriers arise when a metal with a work function (Φm) contacts a semiconductor with a different work function (Φs). Initially, electrons transfer until the Fermi levels of the metal and semiconductor align at equilibrium. For instance, if Φm > Φs, the semiconductor Fermi level is higher than the metal's before contact. The...
Schottky Barriers
Schottky barriers arise when a metal with a work function (Φm) contacts a semiconductor with a different work function (Φs). Initially, electrons transfer until the Fermi levels of the metal and semiconductor align at equilibrium. For instance, if Φm > Φs, the semiconductor Fermi level is higher than the metal's before contact. The...
1.4K
01:28Types Of Superconductors
1.8K
A superconductor is a substance that offers zero resistance to the electric current when it drops below a critical temperature. Zero resistance is not the only interesting phenomenon as materials reach their transition temperatures. A second effect is the exclusion of magnetic fields. This is known as the Meissner effect. A light, permanent magnet placed over a superconducting sample will levitate in a stable position above the superconductor. High-speed trains that levitate on strong...
1.8K