Difference between 1D lattice and 2D lattice on BEC

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Discussion Overview

The discussion revolves around the differences between one-dimensional (1D) and two-dimensional (2D) optical lattices in the context of Bose-Einstein Condensation (BEC). Participants explore theoretical implications, experimental realizations, and the characteristics of these lattices.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants note that in one-dimensional systems, there is typically no phase transition, referencing the Wagner-Mermin theorem, which implies no BEC occurs in such systems.
  • Others argue that real experimental situations involve spatially inhomogeneous systems, which can lead to finite size effects that differ from theoretical predictions in 1D and 2D systems.
  • A participant mentions the Tonks-Girardeau gas as a transition in 1D systems where bosons behave like fermions, suggesting that BEC behavior can vary significantly in low-dimensional structures.
  • One participant clarifies that a 1D optical lattice is created using a pair of laser beams, while a 2D optical lattice involves a configuration that resembles a tube shape.
  • Another participant proposes that achieving a 1D lattice can be done using six laser beams to create three standing wave patterns, allowing for the trapping of atoms at intensity maxima.
  • There is a discussion about how the strength of the trapping potential affects the behavior of atoms in these lattices, with implications for their kinetic energy and movement.

Areas of Agreement / Disagreement

Participants express differing views on the implications of dimensionality for BEC, with some asserting that 1D systems lack BEC due to the Wagner-Mermin theorem, while others highlight exceptions and complexities in real-world scenarios. The discussion remains unresolved regarding the definitive characteristics and behaviors of BEC in 1D versus 2D lattices.

Contextual Notes

The discussion includes references to theoretical theorems and experimental setups, but lacks consensus on the implications of dimensionality for BEC. There are also mentions of specific conditions under which BEC may or may not occur, depending on the lattice configuration and external factors.

Choi Si Youn
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I studied in AMO physics. nowaday, I study about BEC.

I'm wonder, Difference between 1D lattice and 2D lattice on BEC.
In the web, they just explain what they do using that.


Maybe just short word, or sentence, give me a huge knowledge.


Thanks you, and Have a nice day!
 
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I don't know exactly from which part of the "web" you have your information, so I just can guess:
In one dimensional systems, there is usually no phase transition (look for Wagner Mermin theorem), so also no BEC.
 
DrDu said:
In one dimensional systems, there is usually no phase transition (look for Wagner Mermin theorem), so also no BEC.

The Wagner-Mermin theorem is valid for spatially homogeneous systems in the thermodynamic limit. Any real experimental situation necessarily includes spatially inhomogeneous systems, which therefore have finite size. While the thermodynamic limit is usually well justified in 3D, this is usually not the case in real 2D and 1D systems. Accordingly there are several realizations of BEC in lowdimensional structures. I do not know much about 1D, but I know there is a transition from "usual" BEC behaviour towards bosons, which mimic fermions, which is called Tonks-Girardeau gas (see Nature 429, 277-281 (2004) by Peredes et al.). If I remember correctly, also the dependence of the critical temperatur on the system size and particle number differ strongly in 1D and 2D.
 
Oh...'1D','2D' means "Optical lattice's dimension"////
and I found a difference what I wonder, Difference between 1D optical lattice and 2D optical lattice.
1D optical lattice is made by a pair of laser beams , and it makes interference of single standard wave. and 2D optical lattice's shape look like 1D but 2D's shape look like tube.

if that is wrong or something miss, please reply again.
 
I am not an expert on that, but I think the easiest way to achieve a 1D lattice is to use 6 laser beams and therefore 3 standing wave patterns perpendicular to each other. This gives you a situation similar to a solid, where you have the equivalent of fixed lattice sites at the maxima of the standing waves of the crossing area, divided by some trapping potential (the minima of the standing waves). The atoms will be positioned at these intensity maxima. Now you can tune the strength of the trapping potential by varying the intensity of the standing waves. If the trapping potential in a dimension is large compared to the kinetic energy of the atoms, they will be trapped in this dimension. If you lower the trapping potential you will gradually reach the regime, where the atoms can move freely in that dimension.
 

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