Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [bose-einstein-condensate]

A Bose–Einstein condensate is a state of matter of a dilute gas of bosons cooled to temperatures very close to absolute zero. In this state, a large fraction of the bosons occupy the *lowest quantum state* so that macroscopic quantum phenomena are in evidence. Use for all related BEC processes.

0
votes
0answers
22 views

JILA Rubidium-87 Bose Einstein condensate

Why was the observation of Bose-Einstein condensation by JILA considered so special? I was under the impression that they were not nearly the first group to observe it, since it was observed with ...
0
votes
1answer
25 views

What's “bimodal” about BEC velocity distributions?

I was just reviewing some papers discussing Bose-einstein condensation, specifically "Creation of a Bose-condensed gas of 87Rb by laser cooling" by Hu et al., and I saw repeated references to the ...
1
vote
1answer
27 views

Macroscopic population of excited states for Bose-Einstein condensation?

I am currently learning about Bose-Einstein condensation (BEC). I understand that the ground state is rapidly populated when the temperature goes below the critical temperature. This macroscopic ...
0
votes
0answers
9 views

Physical interpretation of Bogolyubov sound with zero momentum in BEC

The point with zero momentum in the spectrum of acoustic phonon corresponds to a translation of the crystal. Is there an interpretation like this of the Bogolyubov sound in BEC? I have read that in ...
8
votes
1answer
62 views

Why is the density of a BEC so low?

I've just begun reading C. Pethick and H. Smith's textbook "Bose-Einstein condensation in dilute gases" (Cam. Uni. Press). In the Introduction, they contrast the density of atoms at the centre of a ...
2
votes
0answers
17 views

Bose-Einstein Condensate bonding

How would a material bond with a BEC? Would it have valence electrons? If you were to have a couple hundred atoms in BEC, would they bond with a couple hundred other atoms, a lower amount that how ...
0
votes
1answer
37 views

Is it BEC-BCS crossover the natural framework to explain superconductivity from ultracold atoms?

I know that superfluidity and superconductivity have very distinct characteristics and have specific theories. However, it seems that in ultra-cold atomic gases these phenomena can be understood by a ...
1
vote
1answer
28 views

Phase change into Bose-Einstein Condensate

I am a high school chemistry/physics teacher and I was just wondering what the phase change into/out of a Bose-Einstein Condensate is called? Thanks!
0
votes
1answer
40 views

Why we can't write low energy effective field theory for a gapless system?

Assume that we have an Hamiltonian $$H=H_0+H_{int}$$ where $H_0$ has gappless excitations and $H_{int}$ has usual two body interactions. If $H_0$ were gapped I would able to get low energy effective ...
0
votes
0answers
18 views

Heating A Condensate

There is so much literature out there on Bose Condensates, that it is literally all about the cooling of a gas. But I am interested in the physics of the condensate heating up - can someone explain ...
0
votes
0answers
14 views

Can I distinguish a Bose-Einstein Condensate of composite bosons from one of elementary bosons?

The only requirement for an ensemble of particles to undergo a transition into a BEC is to be bosons. But two fermions also make a bosons. Are there physical, measureable implications of a BEC being ...
0
votes
0answers
35 views

Where is the gauge symmetry in an ideal Bose gas?

It seems in the literature that there is a certain notion of a “macroscopic wavefunction” associated with a Bose-Einstein system (see this PSE answer) which exhibits a global $U(1)$-phase symmetry. ...
3
votes
2answers
52 views

Do macroscopic bodies also show quantum nature at extremely low temperatures?

If we consider atoms or molecules and cool them to extremely low tempertures, will they also show quantum nature. Will their wave nature also get dominated? And if they are bosons, will they become a ...
0
votes
1answer
19 views

How to write a wave-fuction of bose einstein condesate bosons in second quantization representation?

Can we write wave function of bose einstein condensation like this $|\psi \rangle=\frac{{c^{\dagger}}^N}{ \sqrt{N!}} |0\rangle$. Or it will be different?
0
votes
0answers
12 views

super bunching effect of bosons

Let say we consider a $N$ pair of elementry bosons (i.e $N$ composite bosons). At very low temperature these bosons will condense into the ground state. If we find the mean occupation number $\langle ...
5
votes
0answers
50 views

Bose Condensation; interacting vs. non-interacting

I have some problems unifying, the two way I learned how a Bose condensate appears. The main problem is that the observables seem to be quite different. In statistical physics lecture one starts with ...
4
votes
2answers
122 views

Why do composite bosons form a BEC?

I found this question here but it does not fully answer my question. The answer there was that "composite bosons can occupy the same state when the state is spatially delocalized on a scale larger ...
1
vote
2answers
41 views

What is the criteria of trapped ideal gas to form Bose-Einstein condensate (BEC)?

If we have ideal gas of bosons in a trapped harmonic potential, is the only necessary thing for BEC is a temperature less than the transition temperature? Or is there any other things we should keep ...
2
votes
2answers
58 views

What happens when we cool down the gas of non-identical particles?

For gas of identical particles, when we cool it down to extremely low temperature we can see one of two types of behaviour depending on the symmetry of wavefunction with respect to argument ...
0
votes
1answer
56 views

Order parameter and Bose-Einstein condensation

I want to study about order parameter and symmetry breaking related to bose einstein condensation in interacted system. Which book i should read? also i want to learn this in second quantization ...
0
votes
0answers
15 views

Free energy of non-interacting bosons in mean field

The result As a mathematician I am currently struggling to understand Tóth's Phase transition in an interacting Bose system. An application of the theory of Ventsel' and Freidlin. The free energy (...
1
vote
0answers
31 views

What are the anti-commutation relations needed to be fulfilled by fermionic Bogoliubov transformation?

Bogoliubov transformations are a well used tool to get rid off interaction terms in second quantized Hamiltonians. I'm interested in the fermionic Bogoliubov transformation used in BCS theory, e.g. \...
0
votes
0answers
82 views

Is the ground state a Schrödinger cat state?

Consider the following Bose-Hubbard Hamiltonian which describes a Bose-Einstein condensate confined in a two-well potential: $$ H= -T(a_L^\dagger a_R + a_L a_R^\dagger ) + \frac{U}{2}(n_L^2+n_R^2-...
0
votes
0answers
27 views

What is the super-bunching effects of composite boson?

What is the super-bunching effects of composite boson ?
1
vote
3answers
54 views

In what conditions we can take ground state energy $E_0$ equal to zero?

Like in 3D harmonic oscillator , $E_m = {h} \omega {(m_x +m_y + m_z + 3/2)}$, At ground state energy $m=0$ and $ E_m = h \omega(3/2)$. While discussing Bose-Einstein condensation, for calculations we ...
3
votes
1answer
70 views

Bose condensate in 4d

Could a boson gas condensate in a hypervolume $V$ in 4D? How can I find its critical temperature and the heat capacity? In the books it just said volume $V$, it does not specify the dimension. My ...
1
vote
1answer
45 views

Why we consider identical particles for Bose-Einstein condensation?

Why we consider identical particles like identical composite bosons for BEC. Why we do not consider non identical particles of differnt masses etc?
2
votes
1answer
71 views

Why do bosonic atoms behave like they do?

Why do bosonic particles behave the way they do? Why doesn't the Pauli exclusion principle affect the electrons, protons, and neutrons of the atoms at temperatures close to absolute zero? How does ...
0
votes
1answer
61 views

“General” for time evolution of quantum state

I am reading a book in which at some point they find the time-evolved wavefunction $\phi_0(\mathbf{r},t)$ from the static $\phi_0(\mathbf{r})$. They say that "employing the Heisenberg time evolution ...
0
votes
1answer
60 views

Feshbach resonance and the Gross-Pitaevskii equation

I have a question about Feshbach resonance and the (generalized) Gross-Pitaevskii equation. If we consider a BEC at a finite temperature $T_{BEC}$ and a static mean-field thermal cloud at temperature $...
0
votes
1answer
37 views

What is *diagonal* long range order?

I have seen this question about off-diagonal long range order in superfluids. What’s the difference and the significance between long range diagonal and off-diagonal long range order?
0
votes
1answer
54 views

What is quantum fluctuation in the Bose-Einstein condensates theory?

I would like to understand what quantum fluctuation really means. I think it's the particles that are not in the ground state. Am I right? But then, what are the differences between quantum ...
1
vote
0answers
30 views

What is the link between superfluids and BEC?

i’m studying superfluids (in particular $^4 He$) and one of the first theorical apporoach was with Bose-Einstein condensation and i know that we can calculate the $T_c$ and it is close to the the ...
0
votes
0answers
25 views

why for two level system we consider both energy level while finding number of bosons in ground state?

Let suppose we have N number of particles in two level system. .Effective number of cobosons in ground state is $ <n_0>$ that can be written as $<\hat{n}_0>= Tr [\hat{n_0}\rho ]$ where $\...
2
votes
2answers
127 views

Partition function for an interacting bosonic mode

Let us assume a single bosonic mode, in equilibrium with a reservoir. For a non-interacting Bose gas, the partition function becomes $\mathcal{Z_\text{nonint}}=\sum_{N=0}^\infty e^{-\beta(\epsilon-\...
0
votes
0answers
18 views

Volume in first octant

Here we are finding number of state less than energy E for particle trapped in 3D harmonic potential .For large value of E as compare to hw , we assumed energy levels as continuous.And we introduces ...
0
votes
1answer
28 views

Is mean and average occupation number same?

In Bose distribution we have formula to find number of particles in quantum state .Is mean occupation number and average occupation number same ?
4
votes
0answers
32 views

Experimental challenges of increasing the size of a Bose-Einstein condensate

My question is partially inspired by this question. I know that BECs have been created whose side lengths are on the order of microns, while others have managed to make a side length of approximately $...
0
votes
0answers
77 views

Chemical potential in Bose-Einstein condensation

For a Bose gas, we know that when temperature goes to zero, chemical potential also reach to zero. At $T=0$ all bosons fall into ground state and thus chemical potential is also zero at $T=0$. Also ...
1
vote
1answer
78 views

Bose Einstein Condensation in Grand canonical ensemble

Why we develop formalism of Bose Einstein Condensation in framework of grand canonical ensemble ?
0
votes
0answers
29 views

Composite behavior of composite bosons with the help of entanglement

Are there any good books related to composite bosons using quantum information approach or that can help to understand Bose Einstein condensation of composite bosons?
1
vote
1answer
35 views

Bose gas Hamiltonian in second quantization with indefinite parity potential

In the book Bose-Einstein Condensation by Pitaevski, Lev; Petrovitch, and Sandro Stringari (Oxford University Press), the Hamiltonian for weakly interacting Bose gas reads as, $$H=\sum\dfrac{p^2}{2m}\...
0
votes
0answers
23 views

How self consistency condition works for a superconductors which is finite and does not have periodic boundary condutions?

So if a superconducting system has periodic boundary conditions the s wave superconducting order parameter calculation by self consistency condition is pretty straightforward. However what if I have ...
3
votes
1answer
98 views

Bose-Einstein condensation summation to integral

I have a question about Bose-Einstein condensation. Namely, people say that if we go from the summation over the number of particles to an integral using the density of states, we make a flaw in the ...
2
votes
1answer
87 views

How is it possible to produce a Bose-Einstein condensate of astrophysical dimension?

There is simple mechanism behind such a production and it suggests that a cloud made of bosons could collapse gravitationally into an equilibrium polytrope in the condensate phase. Assuming that ...
1
vote
1answer
146 views

Bose-Einstein condensation in 1D harmonic oscillator and its density of states

I have troubles understanding how (and whether) Bose-Einstein condensation works in 1-D harmonic oscillator. From my calculation it seems that in limit of infinite number of particles, almost all of ...
1
vote
0answers
37 views

Does zero resistance mean that there are no energy exchanging processes between particles in superconductor? [closed]

I was just knowing little bit about bose einstein condensate then I came across superconductor. In the bose einstein condensate particles have same energy levels and they can not escape the level or ...
1
vote
0answers
36 views

Inflation of the Universe as Bose Einstein Condensate (Literature)

I'm searching for literature in the field of cosmological models which use a Bose-Einstein-Condensate (BEC) to model the process of inflation. Especially the analytical results the cubic BEC models ...
2
votes
3answers
133 views

Is BEC the same as entanglement?

I understand that Bose Einstein condensate is: A Bose–Einstein condensate (BEC) is a state of matter of a dilute gas of bosons cooled to temperatures very close to absolute zero. Under such ...
2
votes
3answers
171 views

Is the Bose-Einstein condensation a single particle phenomenon?

BEC occurs for noninteracting Bosons. Can we conclude that it can be described with a single particle? What is the significance of the number of the particles?