高温超伝導体では,超伝導性と反鉄磁性が混ざらない
I Bozovic1, G Logvenov, M A J Verhoeven
1Oxxel GmbH, Technologiepark Universitaet, Bremen 28359, Germany. ibozovic@pacbell.net
Nature
|April 25, 2003
まとめ
高温超伝導性理論は,反鉄磁気と超伝導性の状態は,薄い層でも混じり合わない. ドーピングは,バンドギャップ内で新しい電子状態を生み出すように見える.
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
- 量子力学は,量子力学という
背景:
- 高温超伝導性の理論は,しばしばそれを反鉄磁力学と結びつける.
- 一般的な仮定は,ドーピングは,親化合物のバレンスの帯に穴を作り,超伝導性につながるということです.
- これらのモデルは,類似のエネルギー状態による反鉄磁気と超伝導相の混合を予測しています.
研究 の 目的:
- 超薄層の材料における反鉄磁性と超伝導性の関係を調査する.
- 高温超伝導性の支配的なモデルをテストするために.
- ナノスケールで反鉄磁性と超伝導性の相が混合しているかどうかを判断する.
主な方法:
- 1ユニットセル厚のLa2CuO4 (反鉄磁性) とLa1.85Sr0.15CuO4 (超伝導) の層を製造する.
- La2CuO4バリアを通過する超電流の流れの測定.
- La1.85Sr0.15CuO4層の超伝導性特性の特徴について.
主要な成果:
- 抗鉄磁性La2CuO4層は絶縁性であり,超電流を完全に遮断し,衰退の長さは1年であった.
- 超伝導性のLa1.85Sr0.15CuO4層は,単独で超伝導性を示した.
- これらの発見は,このスケールでの反鉄磁性と超伝導性の相混合の欠如を示しています.
結論:
- 実験結果は,現在のほとんどの高温超伝導性理論と矛盾しています.
- 相混合の欠如は,反鉄磁性と超伝導性が,これまで考えられていたよりもはっきりしている可能性があることを示唆しています.
- ドーピングは,単に値帯に穴を開くのではなく,バンドギャップ内の新しい電子状態を誘導する可能性があります.
さらに関連する動画
09:06Visualizing Uniaxial-strain Manipulation of Antiferromagnetic Domains in Fe1+YTe Using a Spin-polarized Scanning Tunneling Microscope
Published on: March 24, 2019
04:51Comparison of Two Different Synthesis Methods of Single Crystals of Superconducting Uranium Ditelluride
Published on: July 8, 2021
関連する概念動画
Superconductor
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...
Types 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...
Ferromagnetism
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...
Paramagnetism
Paramagnets are materials with unpaired electrons that possess a finite magnetic moment. In the absence of a magnetic field, these moments are randomly oriented, and thus the net moment is zero. Under an external field, a torque acting on the moments tends to align them along the field's direction. However, the random thermal motion of electrons produces a torque opposite to the external field and tries to disorient the moments. These two competing effects align only a few moments along the...
Theory 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,...
Magnetostatic 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...
