高温インターフェースの超伝導性は,金属と絶縁性銅酸化物との間の超伝導性です
A Gozar1, G Logvenov, L Fitting Kourkoutis
1Brookhaven National Laboratory, Upton, New York 11973-5000, USA.
Nature
|October 10, 2008
まとめ
研究者は,新しい酸化銅二重層で,高トランジション温度 (高T ((c)) 超伝導性を達成しました. この強力な現象は,オゾン曝露後に50Kを超えて,インターフェースで発生し,量子研究のための新しい道を開きます.
科学分野:
- 凝縮物質物理学 凝縮物質物理学
- マテリアルサイエンス 材料科学
- ナノテクノロジー ナノテクノロジー
背景:
- インターフェイスで高トランジション温度 (高Tc) 超伝導性を達成することは,アプリケーションと量子現象を縮小された次元で研究するために不可欠です.
- 従来の金属は,電子密度が高いため,インターフェース効果が限られており,超伝導性を阻害します.
- 銅酸化物は,高いT (c) と短いコヒーレンス長さを提供しますが,原子的に完璧なインターフェースを必要とします.
研究 の 目的:
- ナノメートルサイズのインターフェイスに限定された高T (c) 超伝導性を実現し,調査する.
- 絶縁性および金属性銅酸化物の二重層における超伝導性を調査する.
- 強化された超伝導性特性を達成する際のインターフェースの役割を理解する.
主な方法:
- 二重層の製造には,断熱剤 (La(2) CuO(4) と金属 (La(1.55) Sr(0.45) CuO(4) を使用する.
- 二重層における超伝導的移行温度 (T(c)) の特徴.
- 二重層をオゾンに曝露し,T (c) 強化を調査する.
主要な成果:
- 超伝導性は,La(2) CuO(4) とLa(1.55) Sr(0.45) CuO(4) の二重層で観察され,T(c) は約15Kまたは30Kであった.
- 超伝導性は2〜3nmの狭いインターフェース領域に限られていた.
- オゾン曝露は,1~2ユニット細胞のインターフェース層から発生したT (c) を50K以上に大幅に増加させた.
結論:
- 新しい二酸化銅層は,強固な,インターフェース限定の超伝導性を示す.
- 原子の完璧性と特定の層配列は,これらのシステムで高いT (c) を達成するために重要である.
- オゾン処理は,インターフェースの超伝導性を大幅に強化する経路を提供し,インターフェースの重要な役割を強調します.
関連する概念動画
02:32Bonding in Metals
Metallic bonds are formed between two metal atoms. A simplified model to describe metallic bonding has been developed by Paul Drüde called the “Electron Sea Model”.
01:24Superconductor
A substance that reaches superconductivity, a state in which magnetic fields cannot penetrate, and there is no electrical resistance, is referred to as a superconductor. In 1911, Heike Kamerlingh Onnes of Leiden University, a Dutch physicist, observed a relation between the temperature and the resistance of the element mercury. The mercury sample was then cooled in liquid helium to study the linear dependence of resistance on temperature. It was observed that, as the temperature decreased, the...
01:28Types Of Superconductors
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...
01:17Theory of Metallic Conduction
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,...
01:28Magnetostatic Boundary Conditions
An electric field suffers a discontinuity at a surface charge. Similarly, a magnetic field is discontinuous at a surface current. The perpendicular component of a magnetic field is continuous across the interface of two magnetic mediums. In contrast, its parallel component, perpendicular to the current, is discontinuous by the amount equal to the product of the vacuum permeability and the surface current. Like the scalar potential in electrostatics, the vector potential is also continuous...
01:24Metal-Semiconductor Junctions
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 semiconductor's...
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 semiconductor's...