原子Bose-Hubbardシステムにおけるフェーズスリップ誘発的消散

D McKay¹, M White, M Pasienski

¹Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801, USA.

Nature

|May 3, 2008

まとめ

段階スライプは,超冷たい原子のボース・ハバード系における分散を制御する. この研究は,量子トンネリングと相転移の熱活性化を明らかにし,超流体分散におけるそれらの役割を明らかにしています.

科学分野:

原子,分子,光学物理学
凝縮物質物理学凝縮物質物理学
量子ガスとは,量子ガスのことです.

背景:

段階スライプは,ボゾン系における分散に極めて重要であり,超流動性や超伝導性に影響を及ぼします.
小規模な超伝導体における相転移の理解は,騒音と混乱のために困難です.
以前の研究は,しばしば高温の熱変動に焦点を当て,低温の量子効果がよりはっきりしないようにしました.

研究の目的:

清潔なボゼ・ハバード系内の消散における相滑落の役割を調査する.
光学格子における超冷たい原子の低速度状態を調査する.
消散強度の温度依存性とその基礎となるメカニズムを測定する.

主な方法:

3D光学格子に閉じ込められた超冷たい原子の輸送を実験的に研究する.
制御不能の変数を最小限に抑えるために,クリーンでよく特徴づけられたボゼ・ハバード系を使用しています.
原子運動の減圧率を測定し,飛行時間画像を通して運動誘発の特徴を観察する.

主要な成果:

段階のスライプが,超冷たい原子のボゼ・ハバード系における消散を引き起こすことを実証した.
ゼロ温度ダッピングを含むモデルに適したダッピング率を観測した.
低温でのフェーズスリップの量子トンネリングから,より高い温度での熱活性化へのクロスオーバーを特定しました.

結論:

超流体系における分散を制御するフェーズスライプの基本的役割を明らかにした.
量子トンネリングとフェーズスリップの熱活性化メカニズムに関する実験的証拠を提供した.
ボーゼ・ハバードシステムは,ボゾン散乱の理論のための貴重なテストベッドとして機能し,薄膜の現象の理解を伝えることができます.

さらに関連する動画

09:09

Safe Experimentation in Optical Levitation of Charged Droplets Using Remote Labs

Published on: January 10, 2019

08:19

Induction of Microstreaming by Nonspherical Bubble Oscillations in an Acoustic Levitation System

Published on: May 9, 2021

関連する概念動画

02:39

Phase Transitions: Vaporization and Condensation

The physical form of a substance changes on changing its temperature. For example, raising the temperature of a liquid causes the liquid to vaporize (convert into vapor). The process is called vaporization—a surface phenomenon. Vaporization occurs when the thermal motion of the molecules overcome the intermolecular forces, and the molecules (at the surface) escape into the gaseous state. When a liquid vaporizes in a closed container, gas molecules cannot escape. As these gas phase molecules...

02:33

Phase Transitions: Sublimation and Deposition

Some solids can transition directly into the gaseous state, bypassing the liquid state, via a process known as sublimation. At room temperature and standard pressure, a piece of dry ice (solid CO2) sublimes, appearing to gradually disappear without ever forming any liquid. Snow and ice sublimate at temperatures below the melting point of water, a slow process that may be accelerated by winds and the reduced atmospheric pressures at high altitudes. When solid iodine is warmed, the solid sublimes...

01:23

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...

01:28

Induced Electric Dipoles

A permanent electric dipole orients itself along an external electric field. This rotation can be quantified by defining the potential energy because the external torque does work in rotating it. Then, the potential energy is minimum at the parallel configuration and maximum at the antiparallel configuration. While the former is a stable equilibrium, the latter is an unstable equilibrium.
Since the absolute value of potential energy holds no physical meaning, its zero value can be chosen as per...

01:25

Deactivation Processes: Jablonski Diagram

Luminescence, the emission of light by a substance that has absorbed energy, is a process that involves the interaction of molecules with light. The energy-level diagram, or Jablonski diagram, is a graphical representation of these interactions, illustrating the various states and transitions a molecule can undergo. In a typical Jablonski diagram, the lowest horizontal line represents the ground-state energy of the molecule, which is usually a singlet state. This state represents the energies...

01:12

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...

関連する実験動画