超伝導体におけるピーク効果体制における2つの共存する渦形相
M Marchevsky1, M J Higgins, S Bhattacharya
1NEC Research Institute, Princeton, New Jersey 08540, USA. marchev@research.nj.nec.com
Nature
|February 24, 2001
まとめ
NbSe2のような超伝導体のピーク効果は,異なるピニング強度を持つ2つの共存する渦状物質相によって説明されます. この相の共存は,乱れによる移行を促し,40年前の謎を解く.
科学分野:
- 凝縮物質物理学 凝縮物質物理学
- 超伝導性に関する研究.
- マテリアルサイエンス 材料科学
背景:
- タイプIIの超伝導体は,ピーク効果として知られる超伝導体から通常の金属への移行の近くで,臨界電流の異常を示します.
- このピーク効果は,流れが消滅する前にピークを迎えるという点で,40年間も説明がつかないままです.
研究 の 目的:
- NbSe2.2におけるピーク効果の根本的なメカニズムを調査する.
- 渦の段階における臨界電流の実際の空間分布を視覚化するために.
主な方法:
- A.C.ホールのスキャニング顕微鏡を使用した.
- NbSe2.2における臨界電流のリアル空間分布を視覚化しました.
主要な成果:
- 異なるピニング強度を持つ2つの異なる渦状物質相を特定し,ピーク効果体制でマクロスケールで共存しました.
- これらの相の組成と変換が,歴史効果と異常な電圧応答を説明することを実証した.
結論:
- 2つの渦状物質相の共存が,NbSe2.2のピーク効果の原因となっている.
- この相共存は,非熱的相変遷の特徴である.
関連する概念動画
Phase Transitions
Whether solid, liquid, or gas, a substance's state depends on the order and arrangement of its particles (atoms, molecules, or ions). Particles in the solid pack closely together, generally in a pattern. The particles vibrate about their fixed positions but do not move or squeeze past their neighbors. In liquids, although the particles are closely spaced, they are randomly arranged. The position of the particles are not fixed—that is, they are free to move past their neighbors to occupy...
¹H NMR: Interpreting Distorted and Overlapping Signals
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
Atomic Nuclei: Nuclear Relaxation Processes
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis, the precessing magnetic moments are randomly oriented around the z-axis. This...
¹H NMR Signal Multiplicity: Splitting Patterns
When protons A and X are coupled, their nuclear spin energy levels are slightly modified. This is because the energy required to excite proton A to a spin state parallel to proton X is slightly different from the energy required for it to become anti-parallel to spin X. Consequently, there are two possible excitation frequencies for A (A1 and A2), depending on the spin state of X, and vice versa. The mutual nature of coupling implies that the difference between frequencies A1 and A2, indicated...
Fermi Level Dynamics
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...
Phase Transitions
A phase transition is the process in which a substance changes from one state of matter to another, like from a solid to a liquid, liquid to gas, or vice versa, at a specific temperature and under given pressure conditions. This change is spontaneous and is affected by alterations in temperature and pressure. These parameters impact the strength of the forces between molecules (intermolecular forces) in the substance.During a phase transition, both the initial and final phases of the substance...


