Few-Body physics with ultracold K and Rb: Efimov physics and the Bose polaron

Transcription

1 Few-Body physics with ultracold K and Rb: Efimov physics and the Bose polaron 1

2 Dual species quantum gases with tunable interactions mixing vs. phase separation Polarons beyond mean field LHY droplets Efimov physics

3 HETERONUCLEAR EFIMOV PHYSICS Three non-identical bosons Three identical bosons K

4 Polaron physics Technologically important semiconductors Superconductors L. D. Landau Electron Coupling Lattice phonons Formation of quasiparticle: Polaron S. I. Pekar Electrons in solids

5 OUTLINE Motivation Quantum gases with tunable interactions Efimov physics in K-Rb mixtures Disappearance of Efimov resonances in K The Bose polaron Conclusion

6 EXPERIMENTAL SEQUENCE Selective cooling of Rb Sympathetic cooling of K 39 K Quadropole trap QUIC trap Optical dipole trap Wacker et. al. Phys. Rev. A 92, (2015)

7 FESHBACH RESONANCES IN ULTRACOLD GASES Applications: BEC formation control mean field interaction associate molecules Efimov physics Chin et. al. 2010

8 BOSE-EINSTEIN CONDENSATION F=1,m f =-1>

9 FESHBACH RESONANCES K-Rb inter species resonance K-K inter state resonance F=1,m f =-1> F=1,m f =-1>+ F=1,m f =0>

10 OUTLINE Motivation Quantum gases with tunable interactions Efimov physics in K-Rb mixtures Disappearance of Efimov resonances in K The Bose polaron Conclusion

11 EFIMOV PHYSICS EXAMPLES OF UNIVERSALITY R. Grimm Group M. Weidemüller Group M. Inguscio Group C. Chin Group

12 HETERONUCLEAR EFIMOV PHYSICS Three identical bosons Three non-identical bosons Barontini et. al. 2009

13 HETERONUCLEAR EFIMOV PHYSICS Three non-identical bosons Barontini et. al Bloom et. al. 2013

14 HETERONUCLEAR EFIMOV PHYSICS Three non-identical bosons Barontini et. al Bloom et. al K + 87 Rb system One more isotope to study!

15 HETERONUCLEAR EFIMOV PHYSICS Efimov physics are explored by studying decay rates at various interactions

16 LOSSES IN MIXTURES Heating: (single species) Well known: Use: Solve and fit differential equations: Extract:

17 HETERONUCLEAR EFIMOV PHYSICS Three non-identical bosons Barontini et. al Bloom et. al. 2013

18 HETERONUCLEAR EFIMOV PHYSICS Dispensers providing atomic vapor of K and Rb Potassium dispenser Wikipedia 41 K 87 Rb

19 HETERONUCLEAR EFIMOV PHYSICS Target state: p-wave resonance

20 HETERONUCLEAR EFIMOV PHYSICS No observable Efimov resonances! No observable Efimov resonances! Bloom et. al No observable Efimov resonances!

21 CONCLUSION AND OUTLOOK No observable atomic Efimov resonances in KRb below 2000 a 0 Restores universality Find 39 K- 87 Rb dimer resonance L. J. Wacker, N. B. Jørgensen, D. Birkmose, N. Winter, M. Mikkelsen, J. Sherson, N. Zinner, and J. J. Arlt Phys. Rev. Lett. 117, (2016)

22 OUTLINE Motivation Quantum gases with tunable interactions Efimov physics in K-Rb mixtures Disappearance of Efimov resonances in K The Bose polaron Conclusion

23 EFIMOV PHYSICS IN 39 K M. Inguscio Group

24 EFIMOV RESONANCE REGIONS

25 AIMS Observation of second Efimov resonance Test of universality at adjacent Feshbach resonances

26 EXPERIMENTAL SEQUENCE 39 K BEC T = 42 nk a max = a 0

27 ANALYSIS OF FIRST RESONANCE S. Roy et al., Phys. Rev. Lett. 111, (2013) Good agreement of experimental results at T=100nK

28 ANALYSIS OF SECOND RESONANCE Surprises: 1. No clear second resonance 2. First resonance is extremely weak

29 T DEPENDENCE OF FIRST RESONANCE 80nK 120nK 250nK 500nK

30 TEMPERATURE DEPENDENCE No decrease of recombination rate in theory (N. Zinner) Is something missing from theory? Is the measurement suitable?

31 OUTLINE Motivation Quantum gases with tunable interactions Efimov physics in K-Rb mixtures Disappearance of Efimov resonances in K The Bose polaron Conclusion

32 Polarons in ultracold gases Polaron in a solid Polaron in an ultracold gas Energy of the polaron Mean field: Energy Ultracold gases High purity High flexibility Tunable interactions Inverse interaction strength

33 Polarons in ultracold gases Feshbach resonances provide tunable interactions Energy of the polaron Mean field: Energy Inverse interaction strength

34 Polarons in ultracold gases Feshbach resonances provide tunable interactions Energy of the polaron

35 Polarons in ultracold gases General experimental procedure Energy of the polaron Prepare impurity in non interacting state Polaron energy Perform spectroscopy into interacting state Obtain energy shift and repeat for different interactions!

36 Polarons in ultracold gases Results from ultracold Fermi gases Energy of the polaron (Axis reversed)

37 The Bose polaron Three body physics enter! Stronger parallel to solid state physics (phonons are bosons) Enhances losses! Lifetime Is the polaron even well defined? Polaron energy

38 The Bose polaron Our approach Single component 39 K BEC in state Requires Feshbach resonance between two hyperfine states RF pulse performs a fraction of a π pulse polaron energy spin impurities

39 Experimental procedure 39 K BEC RF pulse Three body recombination Loss of atoms Obtain BEC atom number Polaron signal obtained!

40 Polaron spectrum Repulsive polaron Attractive polaron Variational theory including: Density distribution Finite pulse length Three body correlations

41 Quantitative analysis Average energy Signal width Polaron well defined and long lived! Variational theory including: Density distribution Finite pulse length Three body correlations Does not include threebody recombination

42 Conclusion and Outlook First observation of the repulsive and attractive polaron in a BEC Excellent agreement with theory The polaron is long-lived Quantum impurities can now be studied in a bosonic environment systematically! How does temperature affect the polaron? What is the quasiparticle residue of the polaron? Dynamical behaviour of the polaron? Which role does Efimov physics play? published back to back with

43 EFIMOV PHYSICS IN K-Rb AND K-K Experimental work: Nils B. Jørgensen Lars Wacker Jacob Sherson Jan J. Arlt Theoretical work: Nikolaj Zinner Mathias Mikkelsen L. J. Wacker, N. B. Jørgensen, D. Birkmose, N. Winter, M. Mikkelsen, J. Sherson, N. Zinner, and J. J. Arlt Phys. Rev. Lett. 117, (2016)

44 POLARONS IN A BOSE-EINSTEIN CONDENSATE Experimental work: Nils B. Jørgensen Lars Wacker Kristoffer T. Skalmstang Jan J. Arlt Theoretical work: Meera M. Parish Jesper Levinsen Rasmus S. Christensen Georg M. Bruun N. B. Jørgensen, L. Wacker, K. T. Skalmstang, M. M. Parish, J. Levinsen, R. S. Christensen, G. M. Bruun, and J. J. Arlt Phys. Rev. Lett. 117, (2016)

45 Thank you for your attention!