frédéric chevy laboratoire ... -...
TRANSCRIPT
![Page 1: Frédéric Chevy Laboratoire ... - becasim.math.cnrs.frbecasim.math.cnrs.fr/events2/meetings2/workshopCIRM/Day_01/02...S. Laurent. M. Rabinovic. C. Enessa. M. Pierce. M. Delehaye](https://reader034.vdocuments.us/reader034/viewer/2022051722/5aa0ebd67f8b9a0d158ede6d/html5/thumbnails/1.jpg)
Counterflowing superfluids
Frédéric ChevyLaboratoire Kastler Brossel
![Page 2: Frédéric Chevy Laboratoire ... - becasim.math.cnrs.frbecasim.math.cnrs.fr/events2/meetings2/workshopCIRM/Day_01/02...S. Laurent. M. Rabinovic. C. Enessa. M. Pierce. M. Delehaye](https://reader034.vdocuments.us/reader034/viewer/2022051722/5aa0ebd67f8b9a0d158ede6d/html5/thumbnails/2.jpg)
ENS FERMI GROUP
Y. Castin (ENS), S. Stringari (Trento), I. Danaila (Rouen), P. Parnaudeau (Poitiers)
S. JinS. Laurent
M. Rabinovic
C. Enessa
M. Pierce M. Delehaye
D. SuchetFC
T. Reimann
C. Salomon
I. Ferrier-Barbut
![Page 3: Frédéric Chevy Laboratoire ... - becasim.math.cnrs.frbecasim.math.cnrs.fr/events2/meetings2/workshopCIRM/Day_01/02...S. Laurent. M. Rabinovic. C. Enessa. M. Pierce. M. Delehaye](https://reader034.vdocuments.us/reader034/viewer/2022051722/5aa0ebd67f8b9a0d158ede6d/html5/thumbnails/3.jpg)
![Page 4: Frédéric Chevy Laboratoire ... - becasim.math.cnrs.frbecasim.math.cnrs.fr/events2/meetings2/workshopCIRM/Day_01/02...S. Laurent. M. Rabinovic. C. Enessa. M. Pierce. M. Delehaye](https://reader034.vdocuments.us/reader034/viewer/2022051722/5aa0ebd67f8b9a0d158ede6d/html5/thumbnails/4.jpg)
3He/4He phase diagram
![Page 5: Frédéric Chevy Laboratoire ... - becasim.math.cnrs.frbecasim.math.cnrs.fr/events2/meetings2/workshopCIRM/Day_01/02...S. Laurent. M. Rabinovic. C. Enessa. M. Pierce. M. Delehaye](https://reader034.vdocuments.us/reader034/viewer/2022051722/5aa0ebd67f8b9a0d158ede6d/html5/thumbnails/5.jpg)
7Li (boson)
6Li (fermion)
~200µm
![Page 6: Frédéric Chevy Laboratoire ... - becasim.math.cnrs.frbecasim.math.cnrs.fr/events2/meetings2/workshopCIRM/Day_01/02...S. Laurent. M. Rabinovic. C. Enessa. M. Pierce. M. Delehaye](https://reader034.vdocuments.us/reader034/viewer/2022051722/5aa0ebd67f8b9a0d158ede6d/html5/thumbnails/6.jpg)
Achieving double superfluidity withcold atoms
Requirements: •Low abf (no interspecies demixing)•High |aff |(high fermionic Tc)•Positive abb (stable BEC)
6Li – 7Li mixture in the |1>f, |2>f and |2>b
![Page 7: Frédéric Chevy Laboratoire ... - becasim.math.cnrs.frbecasim.math.cnrs.fr/events2/meetings2/workshopCIRM/Day_01/02...S. Laurent. M. Rabinovic. C. Enessa. M. Pierce. M. Delehaye](https://reader034.vdocuments.us/reader034/viewer/2022051722/5aa0ebd67f8b9a0d158ede6d/html5/thumbnails/7.jpg)
6Li
7Li
I. Ferrier-Barbut, et al., Science 345, 1035 (2014)
T/Tcb,f<0.5
Superfluid mixture @ B=832G
![Page 8: Frédéric Chevy Laboratoire ... - becasim.math.cnrs.frbecasim.math.cnrs.fr/events2/meetings2/workshopCIRM/Day_01/02...S. Laurent. M. Rabinovic. C. Enessa. M. Pierce. M. Delehaye](https://reader034.vdocuments.us/reader034/viewer/2022051722/5aa0ebd67f8b9a0d158ede6d/html5/thumbnails/8.jpg)
DYNAMICS OF THE MIXTURES
6
7
2 17.06(1)2 15.40(1)
HzHz
ω πω π
= ×= ×
Coupled Superfluids
6
7
2 16.80(2)2 15.00(2)
HzHz
ω πω π
= ×= ×
Single SuperfluidRatio = (7/6)1/2 =(m7/m6)1/2
See also C. Hammer et al Phys. Rev. Lett. 106, 065302 (2011) for boson-boson superfluid counterflow
![Page 9: Frédéric Chevy Laboratoire ... - becasim.math.cnrs.frbecasim.math.cnrs.fr/events2/meetings2/workshopCIRM/Day_01/02...S. Laurent. M. Rabinovic. C. Enessa. M. Pierce. M. Delehaye](https://reader034.vdocuments.us/reader034/viewer/2022051722/5aa0ebd67f8b9a0d158ede6d/html5/thumbnails/9.jpg)
FREQUENCY SHIFT
Benchmark: Numericalsolution of GPE (P. Parnaudeau/I. Danaila/A. Suzuki)
Sum ruleEffective potential
eff ,7 67 6 6( ) ( ( ))V V g n µ= +r r 06 6 6( ( )) ( )µ n µ V= −r r
0 667 6 6 67
6
( ) ( ) 1 ng n µ V gµ
∂≈ + − ∂
r
(Local Density Approximation)
Harmonic trap: 7 67 6
7 62g n
µωω∆ ∂
≈ −∂
![Page 10: Frédéric Chevy Laboratoire ... - becasim.math.cnrs.frbecasim.math.cnrs.fr/events2/meetings2/workshopCIRM/Day_01/02...S. Laurent. M. Rabinovic. C. Enessa. M. Pierce. M. Delehaye](https://reader034.vdocuments.us/reader034/viewer/2022051722/5aa0ebd67f8b9a0d158ede6d/html5/thumbnails/10.jpg)
OSCILLATION FREQUENCY OF THE BEC
Weak frequency shift (few percents) of the bosons due to the fermions
67 67 7
6
~ 12
g dnd
ω ωµ
−
![Page 11: Frédéric Chevy Laboratoire ... - becasim.math.cnrs.frbecasim.math.cnrs.fr/events2/meetings2/workshopCIRM/Day_01/02...S. Laurent. M. Rabinovic. C. Enessa. M. Pierce. M. Delehaye](https://reader034.vdocuments.us/reader034/viewer/2022051722/5aa0ebd67f8b9a0d158ede6d/html5/thumbnails/11.jpg)
Oscillations of 7Li
Large initial displacement:Damped oscillations
Small initial displacement:•Almost no damping (decay time>4s)•Beatnote (coherent coupling between the twooscillators)
![Page 12: Frédéric Chevy Laboratoire ... - becasim.math.cnrs.frbecasim.math.cnrs.fr/events2/meetings2/workshopCIRM/Day_01/02...S. Laurent. M. Rabinovic. C. Enessa. M. Pierce. M. Delehaye](https://reader034.vdocuments.us/reader034/viewer/2022051722/5aa0ebd67f8b9a0d158ede6d/html5/thumbnails/12.jpg)
Critical velocity
![Page 13: Frédéric Chevy Laboratoire ... - becasim.math.cnrs.frbecasim.math.cnrs.fr/events2/meetings2/workshopCIRM/Day_01/02...S. Laurent. M. Rabinovic. C. Enessa. M. Pierce. M. Delehaye](https://reader034.vdocuments.us/reader034/viewer/2022051722/5aa0ebd67f8b9a0d158ede6d/html5/thumbnails/13.jpg)
LANDAU’S CRITERION
V
2 2
'/ 2
Momentum Conservation :
Energy Conservation /2+ :
M MMV MV ε
= +
′= k
V V k
The motion of the impurity is damped by the creation of elementary excitations if
min kc kV V
kε ≥ =
V’
,εkk
= sound velocity for a linear excitation spectrum ε=kc
2 2. / 2k k mε= +k V kε≥kV ≥
![Page 14: Frédéric Chevy Laboratoire ... - becasim.math.cnrs.frbecasim.math.cnrs.fr/events2/meetings2/workshopCIRM/Day_01/02...S. Laurent. M. Rabinovic. C. Enessa. M. Pierce. M. Delehaye](https://reader034.vdocuments.us/reader034/viewer/2022051722/5aa0ebd67f8b9a0d158ede6d/html5/thumbnails/14.jpg)
Critical velocity
cFcb
![Page 15: Frédéric Chevy Laboratoire ... - becasim.math.cnrs.frbecasim.math.cnrs.fr/events2/meetings2/workshopCIRM/Day_01/02...S. Laurent. M. Rabinovic. C. Enessa. M. Pierce. M. Delehaye](https://reader034.vdocuments.us/reader034/viewer/2022051722/5aa0ebd67f8b9a0d158ede6d/html5/thumbnails/15.jpg)
Landau criterion for a superfluidMixture
(Castin et al. Comptes Rendus Physique 16, 241 (2015) arXiv:1408.1326)
1 Excitation in the bosonic superfluid
1 Excitation in the fermionic superfluid
, , ·B B BE ε= +k k k V
Energy-momentum conservation:
, , ' '·F F FE ε= +k k k V
, ,| | min B k F kB F k k
ε ε −+ − ≥
V V
c B FAcoustic Modes: V c c= +
, , ' 0B FE E+ =k k ' 0+ =k k
,, Bε kk, '', Fε kk
See also Abbad et al. EPJD 69, 126 (2015), F. Chevy PRA 91, 063606 (2015), W. Zheng et H. Zhai, Phys. Rev. Lett. 113, 265304 (2014)
![Page 16: Frédéric Chevy Laboratoire ... - becasim.math.cnrs.frbecasim.math.cnrs.fr/events2/meetings2/workshopCIRM/Day_01/02...S. Laurent. M. Rabinovic. C. Enessa. M. Pierce. M. Delehaye](https://reader034.vdocuments.us/reader034/viewer/2022051722/5aa0ebd67f8b9a0d158ede6d/html5/thumbnails/16.jpg)
Critical Velocity
experiment
cF
cF+cB
Similar reduction of vc at MIT and Hamburg for fermions.Possible explanations: finite temperature, vortex nucleation…
![Page 17: Frédéric Chevy Laboratoire ... - becasim.math.cnrs.frbecasim.math.cnrs.fr/events2/meetings2/workshopCIRM/Day_01/02...S. Laurent. M. Rabinovic. C. Enessa. M. Pierce. M. Delehaye](https://reader034.vdocuments.us/reader034/viewer/2022051722/5aa0ebd67f8b9a0d158ede6d/html5/thumbnails/17.jpg)
Validity of Landau’s argument?(see also V.P. Singh et al. arXiv:1509.02168 )
• Argument valid for a constant velocity in an homogeneousmedium.
• But:
Trapping potentialOscillatory motion
vs
Cozzo & Dalfovo, NJP (2003)Crépin, Leyronas & FC under submission
No critical velocity!
![Page 18: Frédéric Chevy Laboratoire ... - becasim.math.cnrs.frbecasim.math.cnrs.fr/events2/meetings2/workshopCIRM/Day_01/02...S. Laurent. M. Rabinovic. C. Enessa. M. Pierce. M. Delehaye](https://reader034.vdocuments.us/reader034/viewer/2022051722/5aa0ebd67f8b9a0d158ede6d/html5/thumbnails/18.jpg)
THANKS FOR YOURATTENTION!