The crossover from weak-coupling Bardeen-Cooper-Schrieffer (BCS) pairing to a Bose-Einstein condensate (BEC) of tightly bound pairs, as a function of the attractive interaction in Fermi systems, has long been of interest to theoretical physicists. The past decade has seen a series of remarkable experimental developments in ultracold Fermi gases that have realized the BCS-BEC crossover in the laboratory, bringing with it fresh new insights into the very strongly interacting unitary regime in the middle of this crossover. In this review, we start with a pedagogical introduction to the crossover and then focus on recent progress in the strongly interacting regime. Although our focus is on new theoretical developments, we also describe three key experiments that probe the thermodynamics, transport, and spectroscopy of the unitary Fermi gas. We discuss connections between the unitary regime and other areas of physics—quark-gluon plasmas, gauge-gravity duality, and high-temperature superconductivity—and conclude with open questions about strongly interacting Fermi gases.


Article metrics loading...

Loading full text...

Full text loading...


Literature Cited

  1. Regal CA, Greiner M, Jin DS. 2004. Phys. Rev. Lett. 92:040403 [Google Scholar]
  2. Zwierlein MW, Stan CA, Schunck CH, Raupach SMF, Kerman AJ, Ketterle W. 2004. Phys. Rev. Lett. 92:120403 [Google Scholar]
  3. Kinast J, Hemmer SL, Gehm ME, Turlapov A, Thomas JE. 2004. Phys. Rev. Lett. 92:150402 [Google Scholar]
  4. Bourdel T, Khaykovich L, Cubizolles J, Zhang J, Chevy F et al. 2004. Phys. Rev. Lett. 93:050401 [Google Scholar]
  5. Chin C, Bartenstein M, Altmeyer A, Riedl S, Jochim S et al. 2004. Science 305:1128–30 [Google Scholar]
  6. Partridge GB, Strecker KE, Kamar RI, Jack MW, Hulet RG. 2005. Phys. Rev. Lett. 95:020404 [Google Scholar]
  7. Zwierlein MW, Abo-Shaeer JR, Schirotzek A, Shunck CH, Ketterle W. 2005. Nature 435:1047–51 [Google Scholar]
  8. Zwerger W. 2011. The BCS-BEC Crossover and the Unitary Fermi Gas Berlin: Springer [Google Scholar]
  9. Ketterle W, Zwierlein MW. 2008. Ultracold Fermi Gases, Proceedings of the International School of PhysicsEnrico Fermi,” ed. M Inguscio, W Ketterle, C Salomon, pp 95–287. Amsterdam: IOS Press
  10. Bloch I, Dalibard J, Zwerger W. 2008. Rev. Mod. Phys. 80:3885–964 [Google Scholar]
  11. Giorgini S, Pitaevskii LP, Stringari S. 2008. Rev. Mod. Phys. 80:41215–74 [Google Scholar]
  12. Chen Q, Stajic J, Tan S, Levin K. 2005. Phys. Rep. 412:11–88 [Google Scholar]
  13. Schafroth MR, Butler ST, Blatt JM. 1957. Helv. Phys. Acta 30:93–134 [Google Scholar]
  14. Eagles DM. 1969. Phys. Rev. 186:456–63 [Google Scholar]
  15. Leggett AJ. 1980. Modern Trends in the Theory of Condensed Matter. Proc. XVIth Karpacz Winter School Theor. Phys.,Karpacz, Poland, pp. 13–27. Berlin: Springer-Verlag
  16. Nozières P, Schmitt-Rink S. 1985. J. Low Temp. Phys. 59:3/4195–211 [Google Scholar]
  17. Keldysh LV. 1995. Bose-Einstein Condensation, ed. A Griffen, DW Snoke, S Stringari, pp. 246–60. Cambridge: Cambridge Univ. Press
  18. de Marco B, Jin DS. 1999. Science 285:1703–6 [Google Scholar]
  19. Petrov DS, Salomon C, Shlyapnikov GV. 2004. Phys. Rev. Lett. 93:090404 [Google Scholar]
  20. Duine RA, Stoof HTC. 2004. Phys. Rep. 396:115–95 [Google Scholar]
  21. Cheng C, Grimm R, Julienne P, Tiesinga E. 2010. Rev. Mod. Phys. 82:1225–86 [Google Scholar]
  22. Bruun GM. 2004. Phys. Rev. A 70:053602 [Google Scholar]
  23. Diener RB, Ho T-L. 2004. The condition for universality at resonance and direct measurement of pair wavefunctions using RF spectroscopy. arXiv:cond-mat/0405174 [cond-mat.other]
  24. Romans MWJ, Stoof HTC. 2005. Phys. Rev. Lett. 95:260407 [Google Scholar]
  25. Randeria M, Duan J-M, Shieh L-Y. 1990. Phys. Rev. B 41:1327–43 [Google Scholar]
  26. Sá de Melo CAR, Randeria M, Engelbrecht JR. 1993. Phys. Rev. Lett. 71:3202–5 [Google Scholar]
  27. Engelbrecht JR, Randeria M, Sá de Melo CAR. 1997. Phys. Rev. B 55:2215153–56 [Google Scholar]
  28. Randeria M. 1995. In Bose-Einstein Condensation Griffin A, Snoke DW, Stringari S. 355–92 Cambridge: Cambridge Univ. Press [Google Scholar]
  29. Sensarma R, Randeria M, Ho T-L. 2006. Phys. Rev. Lett. 96:090403 [Google Scholar]
  30. Combescot R, Kagan MYu, Stringari S. 2006. Phys. Rev. A 74:4042717 [Google Scholar]
  31. Miller DE, Chin JK, Stan CA, Liu Y, Setiawan W et al. 2007. Phys. Rev. Lett. 99:7070402 [Google Scholar]
  32. Paiva T, Scalettar R, Randeria M, Trivedi N. 2010. Phys. Rev. Lett. 104:066406 [Google Scholar]
  33. Randeria M, Trivedi N, Moreo A, Scalettar RT. 1992. Phys. Rev. Lett. 69:2001–4 [Google Scholar]
  34. Trivedi N, Randeria M. 1995. Phys. Rev. Lett. 75:312–15 [Google Scholar]
  35. Randeria M. 1998. International School of Physics “Enrico Fermi” Course CXXXVI on High Temperature Superconductors, ed. G Iadonisi, JR Schrieffer, ML Chiafalo, pp. 53–75. Amsterdam: IOS Press
  36. Gor’kov LP, Melik-Barkhudarov TK. 1961. Zh. Eskp. Theor. Fiz. 40:1452 [Google Scholar]
  37. Diener RB, Sensarma R, Randeria M. 2008. Phys. Rev. A 77:023626 [Google Scholar]
  38. Hu H, Liu X-J, Drummond PD. 2006. Europhys. Lett. 74:4574–80 [Google Scholar]
  39. Bertsch G. 2000. Recent progress in many-body theories. Proc. Int. Conf. Recent Prog. Many-Body Theories. Singapore: World Sci.
  40. Perali A, Pieri P, Strinati GC. 2004. Phys. Rev. Lett. 93:10100404 [Google Scholar]
  41. Hu H, Drummond PD, Liu X-J. 2007. Nat. Phys. 3:7469–72 [Google Scholar]
  42. Haussmann R. 1994. Phys. Rev. B 49:1812975–83 [Google Scholar]
  43. Haussmann R, Rantner W, Cerrito S, Zwerger W. 2007. Phys. Rev. A 75:2023610 [Google Scholar]
  44. Veillette M, Sheehy D, Radzihovsky L. 2007. Phys. Rev. A 75:043614 [Google Scholar]
  45. Nikolić P, Sachdev S. 2007. Phys. Rev. A 75:033608 [Google Scholar]
  46. Ho T-L. 2004. Phys. Rev. Lett. 92:090402 [Google Scholar]
  47. Nishida Y, Son DT. 2006. Phys. Rev. Lett. 97:050403 [Google Scholar]
  48. Nishida Y, Son DT. 2007. Phys. Rev. A 75:063617 [Google Scholar]
  49. Randeria M, Duan J-M, Shieh L-Y. 1989. Phys. Rev. Lett. 62:9981–84 [Google Scholar]
  50. Nussinov Z, Nussinov S. 2006. Phys. Rev. A 74:053622 [Google Scholar]
  51. Nishida Y, Son DT. 2012. The BCS-BEC Crossover and the Unitary Fermi Gas, ed. W Zwerger, pp. 233–75. Berlin: Springer-Verlag
  52. Son DT, Wingate M. 2006. Ann. Phys. 321:1197–224 [Google Scholar]
  53. Werner F, Castin Y. 2006. Phys. Rev. A 74:5053604 [Google Scholar]
  54. Nishida Y, Son DT. 2007. Phys. Rev. D 76:086004 [Google Scholar]
  55. Carlson J, Chang S-Y, Pandharipande VR, Schmidt KE. 2003. Phys. Rev. Lett. 91:050401 [Google Scholar]
  56. Astrakharchik GE, Boronat J, Casulleras J, Giorgini S. 2004. Phys. Rev. Lett. 93:200404 [Google Scholar]
  57. Forbes MM, Gandolfi S, Gezerlis A. 2011. Phys. Rev. Lett. 106:235303 [Google Scholar]
  58. Bulgac A, Drut JE, Magierski P. 2008. Phys. Rev. A 78:2023625 [Google Scholar]
  59. Carlson J, Reddy S. 2008. Phys. Rev. Lett. 100:15150403 [Google Scholar]
  60. Carlson J, Reddy S. 2005. Phys. Rev. Lett. 95:060401 [Google Scholar]
  61. Schirotzek A, Shin Y, Schunck CH, Ketterle W. 2008. Phys. Rev. Lett. 101:14140403 [Google Scholar]
  62. Burovski E, Prokof’ev N, Svistunov B, Troyer M. 2006. Phys. Rev. Lett. 96:160402 [Google Scholar]
  63. Burovski E, Kozik E, Prokof’ev N, Svistunov B, Troyer M. 2008. Phys. Rev. Lett. 101:090402 [Google Scholar]
  64. Goulko O, Wingate M. 2010. Phys. Rev. A 82:053621 [Google Scholar]
  65. Ku MJH, Sommer AT, Cheuk LW, Zwierlein MW. 2012. Science 335:6068563–67 [Google Scholar]
  66. Tan S. 2008. Ann. Phys. 323:122971–86 [Google Scholar]
  67. Tan S. 2008. Ann. Phys. 323:122952–70 [Google Scholar]
  68. Braaten E, Platter L. 2008. Phys. Rev. Lett. 100:20205301 [Google Scholar]
  69. Zhang S, Leggett AJ. 2009. Phys. Rev. A 79:2023601 [Google Scholar]
  70. Werner F, Tarruell L, Castin Y. 2009. Eur. Phys. J. B 68:3401–15 [Google Scholar]
  71. Combescot R, Alzetto F, Leyronas X. 2009. Phys. Rev. A 79:053640 [Google Scholar]
  72. Braaten E, Kang D, Platter L. 2008. Phys. Rev. A 78:053606 [Google Scholar]
  73. Yu Z, Bruun GM, Baym G. 2009. Phys. Rev. A 80:2023615 [Google Scholar]
  74. Stewart JT, Gaebler JP, Drake TE, Jin DS. 2010. Phys. Rev. Lett. 104:235301 [Google Scholar]
  75. Pieri P, Perali A, Strinati GC. 2009. Nat. Phys. 5:10736–40 [Google Scholar]
  76. Schneider W, Randeria M. 2010. Phys. Rev. A 81:2021601 [Google Scholar]
  77. Taylor E, Randeria M. 2010. Phys. Rev. A 81:5053610 [Google Scholar]
  78. Son DT, Thompson E. 2010. Phys. Rev. A 81:6063634 [Google Scholar]
  79. Baym G, Pethick CJ, Yu Z, Zwierlein MW. 2007. Phys. Rev. Lett. 99:19190407 [Google Scholar]
  80. Punk M, Zwerger W. 2007. Phys. Rev. Lett. 99:17170404 [Google Scholar]
  81. Zhang S, Leggett AJ. 2008. Phys. Rev. A 77:3033614 [Google Scholar]
  82. Enss T, Haussmann R, Zwerger W. 2011. Ann. Phys. 326:3770–96 [Google Scholar]
  83. Taylor E, Randeria M. 2012. Phys. Rev. Lett. 109:135301 [Google Scholar]
  84. Wlazłowski G, Magierski P, Drut JE. 2012. Phys. Rev. Lett. 109:020406 [Google Scholar]
  85. Son DT. 2007. Phys. Rev. Lett. 98:2020604 [Google Scholar]
  86. Vogt E, Feld M, Frölich B, Pertot D, Koschorreck M, Köhl M. 2012. Phys. Rev. Lett. 108:7070404 [Google Scholar]
  87. Van Houcke K, Werner F, Kozik E, Prokof’ev N, Svistunov B et al. 2012. Nat. Phys. 8:5366–70 [Google Scholar]
  88. Cao C, Elliott E, Joseph J, Wu H, Petricka J et al. 2011. Science 331:58–61 [Google Scholar]
  89. Stewart JT, Gaebler JP, Jin DS. 2008. Nature 454:7205744–47 [Google Scholar]
  90. Gaebler JP, Stewart JT, Drake TE, Jin DS, Perali A et al. 2010. Nat. Phys. 6:569–73 [Google Scholar]
  91. Stringari S. 2004. Europhys. Lett. 65:749–52 [Google Scholar]
  92. Tey MK, Sidorenkov LA, Guajardo ERS, Grimm R, Ku MJH et al. 2013. Phys. Rev. Lett. 110:5055303 [Google Scholar]
  93. Sidorenkov LA, Tey MK, Grimm R, Hou Y-H, Pitaevskii L, Stringari S. 2014. Nature 498:745278–81 [Google Scholar]
  94. Taylor E, Hu H, Liu X-J, Pitaevskii LP, Griffin A, Stringari S. 2009. Phys. Rev. A 80:5053601 [Google Scholar]
  95. Kinast J, Turlapov A, Thomas JE, Chen Q, Stajic J, Levin K. 2005. Science 307:1296–99 [Google Scholar]
  96. Stewart JT, Gaebler JP, Regal CA, Jin DS. 2006. Phys. Rev. Lett. 97:22220406 [Google Scholar]
  97. Luo L, Clancy B, Joseph J, Kinast J, Thomas JE. 2007. Phys. Rev. Lett. 98:8080402 [Google Scholar]
  98. Nascimbène S, Navon N, Jiang KJ, Chevy F, Salomon C. 2010. Nature 463:72841057–60 [Google Scholar]
  99. Horikoshi M, Nakajima S, Ueda M, Mukaiyama T. 2010. Science 327:5964442–45 [Google Scholar]
  100. Zhou Q, Kato Y, Kawashima N, Trivedi N. 2009. Phys. Rev. Lett. 103:085701 [Google Scholar]
  101. Ho T-L, Zhou Q. 2009. Nat. Phys. 6:2131–34 [Google Scholar]
  102. Policastro G, Son DT, Starinets AO. 2001. Phys. Rev. Lett. 87:081601 [Google Scholar]
  103. Kovtun PK, Son DT, Starinets AO. 2005. Phys. Rev. Lett. 94:11111601 [Google Scholar]
  104. Schäfer T, Teaney D. 2009. Rep. Prog. Phys. 72:12126001 [Google Scholar]
  105. O’Hara KM, Hemmer SL, Gehm ME, Granade SR, Thomas JE. 2002. Science 298:2179–82 [Google Scholar]
  106. Massignan P, Bruun GM, Smith H. 2005. Phys. Rev. A 71:3033607 [Google Scholar]
  107. Bruun GM, Smith H. 2007. Phys. Rev. A 75:4043612 [Google Scholar]
  108. Turlapov A, Kinast J, Clancy B, Le Luo J. 2008. J. Low Temp. Phys. 150:3567–76 [Google Scholar]
  109. Chafin C, Schäfer T. 2013. Phys. Rev. A 87:023629 [Google Scholar]
  110. Romatschke P, Young RE. 2013. Phys. Rev. A 87:053606 [Google Scholar]
  111. Damascelli A, Hussain Z, Shen Z-X. 2003. Rev. Mod. Phys. 75:473–541 [Google Scholar]
  112. Campuzano JC, Norman MR, Randeria M. 2004. The Physics of Superconductors, Vol. 2: Superconductivity in Nanostructures, High-Tcand Novel Superconductors, Organic Superconductors, ed. KH Bennemann, JB Ketterson, pp. 923–92. Berlin: Springer-Verlag
  113. Haussmann R, Punk M, Zwerger W. 2009. Phys. Rev. A 80:063612 [Google Scholar]
  114. Chien C-C, Guo H, He Y, Levin K. 2010. Phys. Rev. A 81:023622 [Google Scholar]
  115. Magierski P, Wlazłowski G, Bulgac A, Drut JE. 2009. Phys. Rev. Lett. 103:21210403 [Google Scholar]
  116. Magierski P, Wlazłowski G, Bulgac A. 2011. Phys. Rev. Lett. 107:145304 [Google Scholar]
  117. Wlazłowski G, Magierski P, Drut JE, Bulgac A, Roche KJ. 2013. Phys. Rev. Lett. 110:090401 [Google Scholar]
  118. Sommer A, Ku M, Roati G, Zwierlein MW. 2011. Nature 472:7342201–4 [Google Scholar]
  119. Nascimbène S, Navon N, Pilati S, Chevy F, Giorgini S et al. 2011. Phys. Rev. Lett. 106:215303 [Google Scholar]
  120. Lee PA, Nagaosa N, Wen X-G. 2006. Rev. Mod. Phys. 78:17–85 [Google Scholar]
  121. Sheehy DE, Radzihovsky L. 2007. Ann. Phys. 322:1790–924 [Google Scholar]
  122. Parish MM, Marchetti FM, Lamacraft A, Simons BD. 2007. Nat. Phys. 3:2124–28 [Google Scholar]
  123. Bulgac A, Forbes MM. 2008. Phys. Rev. Lett. 101:21215301 [Google Scholar]
  124. Chevy F, Mora C. 2010. Rep. Prog. Phys. 73:11112401 [Google Scholar]
  125. Gubbels KB, Stoof HTC. 2012. Phys. Rep. 525:4255–313 [Google Scholar]
  126. Fulde P, Ferrell RA. 1964. Phys. Rev. 135:A55063 [Google Scholar]
  127. Larkin AI, Ovchinnikov YN. 1964. Zh. Eksp. Teor. Fiz. 47:1136–46 [Google Scholar]
  128. Won H, Maki K, Haas S, Oeschler N, Weickert F, Gegenwart P. 2004. Phys. Rev. B 69:180504 [Google Scholar]
  129. Martin C, Agosta CC, Tozer SW, Radovan HA, Palm EC et al. 2005. Phys. Rev. B 71:020503 [Google Scholar]
  130. Alford MG, Schmitt A, Rajagopal K, Schäfer T. 2008. Rev. Mod. Phys. 80:1455–515 [Google Scholar]
  131. Shin Y, Schunck CH, Schirotzek A, Ketterle W. 2007. Nature 451:7179689–93 [Google Scholar]
  132. Liao Y, Rittner ASC, Paprotta T, Li W, Partridge GB et al. 2010. Nature 467(7315):567–69 [Google Scholar]
  133. Orso G. 2007. Phys. Rev. Lett. 98:7070402 [Google Scholar]
  134. Lobo C, Recati A, Giorgini S, Stringari S. 2006. Phys. Rev. Lett. 97:20230402 [Google Scholar]
  135. Chevy F. 2006. Phys. Rev. A 74:6063628 [Google Scholar]
  136. Prokof’ev N, Svistunov B. 2008. Phys. Rev. B 77:020408 [Google Scholar]
  137. Schirotzek A, Wu C-H, Sommer A, Zwierlein MW. 2009. Phys. Rev. Lett. 102:23230402 [Google Scholar]
  138. Petrov DS, Baranov MA, Shlyapnikov GV. 2003. Phys. Rev. A 67:031601 [Google Scholar]
  139. Bertaina G, Giorgini S. 2011. Phys. Rev. Lett. 106:11110403 [Google Scholar]
  140. Sommer A, Cheuk L, Ku M, Bakr W, Zwierlein MW. 2012. Phys. Rev. Lett. 108:4045302 [Google Scholar]
  141. Fröhlich B, Feld M, Vogt E, Koschorreck M, Köhl M et al. 2012. Phys. Rev. Lett. 109:13130403 [Google Scholar]
  142. Ho T-L, Diener RB. 2005. Phys. Rev. Lett. 94:090402 [Google Scholar]
  143. Ohashi Y. 2005. Phys. Rev. Lett. 94:050403 [Google Scholar]
  144. Read N, Green D. 2000. Phys. Rev. B 61:1510267–97 [Google Scholar]
  145. Klinkhamer FR, Volovik GE. 2004. JETP Lett. 80(5):343–47 [Google Scholar]
  146. Gurarie V, Radzihovsky L, Andreev AV. 2005. Phys. Rev. Lett. 94:23230403 [Google Scholar]
  147. Gaebler JP, Stewart JT, Bohn JL, Jin DS. 2007. Phys. Rev. Lett. 98:20200403 [Google Scholar]
  148. Zürn G, Lompe T, Wenz AN, Jochim S, Julienne PS, Hutson JM. 2013. Phys. Rev. Lett 110:13135301 [Google Scholar]
  149. Hoinka S, Lingham M, Fenech K, Hu H, Vale CJ et al. 2013. Phys. Rev. Lett 110:5055305 [Google Scholar]
  150. Veeravalli G, Kuhnle E, Dyke P, Vale CJ. 2008. Phys. Rev. Lett 101:25250403 [Google Scholar]
  151. Törmä P, Zoller P. 2000. Phys. Rev. Lett 85:3487–90 [Google Scholar]

Data & Media loading...

  • Article Type: Review Article
This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error