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Disordered superfluid thin films with cold atoms

Disordered superfluid thin films with cold atoms. S. Krinner, D. Stadler, J. Meineke, J.-P. Brantut and T. Esslinger Institute for Quantum Electronics, ETH Zürich. Motivation. Two – dimensional superconducting thin films Superconductor – Insulator Quantum Phase Transition

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Disordered superfluid thin films with cold atoms

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  1. Disordered superfluid thin films with cold atoms S. Krinner, D. Stadler, J. Meineke, J.-P. Brantut and T. Esslinger Institute for Quantum Electronics, ETH Zürich

  2. Motivation • Two – dimensional • superconducting thin films • Superconductor – Insulator • Quantum Phase Transition • Control Parameter: • Disorder Strength • Film Thickness • Magnetic Field • Mechanism: Bosonic vs Fermionic A. Goldman, N. Markovic; Physics Today 51, 11 (1998) V. Ganthmaker, V. Dolgopolov, Physics-Uspekhi 53, 1 (2010)

  3. Experimental Setup • Degenerate Fermi Gas • Atom number: 1056Li atoms • Temperature: 0.2 TF

  4. Experimental Setup • Degenerate Fermi Gas • Atom number: 1056Li atoms • Temperature: 0.2 TF • Tunable Interactions

  5. Experimental Setup Geometry: Mesoscopic two-dimensional channel connected to two reservoirs J.-P. Brantut et al., Science 337, 1069 (2012)

  6. Inducing a chemical potential bias Symmetric position

  7. Inducing a chemical potential bias Symmetric position Shift trap (slow)

  8. Inducing a chemical potential bias Symmetric position Shift trap (slow) Evaporativecooling

  9. Inducing a chemical potential bias Symmetric position Shift trap (slow) Evaporativecooling Shift trap back (fast)

  10. Projection of a disordered potential Tuning parameter: Disorder strength

  11. Length scales Disorder: Correlation length

  12. Length scales Disorder: Correlation length BEC: Molecule pair size

  13. Length scales Disorder: Correlation length Unitary Fermi Gas: pair size

  14. BEC - Resistance of disordered thin film S. Krinner et al., PRL 110, 100601 (2013)

  15. BEC - Breakdown of superfluid flow S. Krinner et al., PRL 110, 100601 (2013)

  16. BEC - Breakdown of superfluid flow S. Krinner et al., PRL 110, 100601 (2013)

  17. BEC - Breakdown of superfluid flow Classical Percolation Threshold: S. Krinner et al., PRL 110, 100601 (2013)

  18. Transport properties – Unitary Fermi Gas

  19. Transport properties – Unitary Fermi Gas

  20. Transport properties – Unitary Fermi Gas Percolation threshold for pairs

  21. Insitu observation of a disordered Fermi Gas 20 Increasing disorder strength

  22. Insitu observation of a disordered Fermi Gas V H H V H V Increasing disorder strength

  23. Percolation analysis

  24. Percolation analysis Level

  25. Percolation analysis Level

  26. Percolation analysis Level

  27. Percolation analysis Level

  28. Percolation analysis Level

  29. Percolation analysis Level

  30. Percolation analysis Level /

  31. Percolation analysis Level / /

  32. Percolation analysis

  33. Percolation analysis Fragmented Regime Pair percolation threshold Smooth Regime

  34. Conclusion – Unitary Fermi Gas (arXiv soon) Increasing Disorder

  35. Outlook: Thermoelectricity J.-P. Brantut et al., arXiv: 1306.5754

  36. Lithium Team J.-P. Brantut D. Stadler S. Krinner J. Meineke T. Esslinger We acknowledge fruitful discussions with: J. Blatter, T.Bourdel, A. Georges, T. Giamarchi, V. Josse, C. Kollath, P. Lugan, C. Mueller, L.Pollet, T. Roscilde, D. Shahar, V. Shenoy, A. Zheludev and W. Zwerger.

  37. Summary 1) Transport measurements: Classical Percolation Threshold: S. Krinner et al., PRL 110, 100601 (2013) Percolation threshold for pairs 2) Insitu study

  38. Length scales Disorder: Correlation length Unitary Fermi Gas: Pair size Coherence length

  39. Disorder-induced breakdown of superfluid flow Classical Percolation Threshold: S. Krinner et al., arxiv:1211.7272 (2012), accepted in PRL

  40. Length scales

  41. Outlook Strongly correlated transport through projected structures

  42. Current flow Exponential decay of atom number imbalance C R 0.1 Finite resistance although transport through channel is ballistic!? 0 0.4 0.8 time (s)

  43. Conduction as transmission Conduction is transmission from one reservoir to another (Landauer)

  44. Conduction as transmission Conduction is transmission from one reservoir to another (Landauer) Contact resistance: Reflection at the contacts

  45. Conduction as transmission Conduction is transmission from one reservoir to another (Landauer) Contact resistance: Reflection at the contacts Dissipation takes place deeply inside the reservoirs J.-P. Brantut et al., Science 337, 1069 (2012)

  46. Why do we not see Josephson oscillations? Length scales : Channel: 30 µm Coherence length: 1µm Time scales : Transport time: 20 ms Chemical potential diff.: 3 kHz The current has no chance to reverse

  47. Disorder-induced breakdown of superfluid flow

  48. Disorder-induced breakdown of superfluid flow

  49. Drift velocity Density independent quantity: Drift velocity: vd

  50. Disorder-induced breakdown of superfluid flow Classical percolation threshold Classical Percolation Threshold:

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