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Liu R, Wang W, Cui X. Quartet Superfluid in Two-Dimensional Mass-Imbalanced Fermi Mixtures. PHYSICAL REVIEW LETTERS 2023; 131:193401. [PMID: 38000427 DOI: 10.1103/physrevlett.131.193401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 09/25/2023] [Accepted: 10/19/2023] [Indexed: 11/26/2023]
Abstract
Quartet superfluid (QSF) is a distinct type of fermion superfluidity that exhibits high-order correlation beyond the conventional BCS pairing paradigm. In this Letter, we report the emergent QSF in 2D mass-imbalanced Fermi mixtures with two-body contact interactions. This is facilitated by the formation of a quartet bound state in vacuum that consists of a light atom and three heavy fermions. For an optimized heavy-light number ratio 3:1, we identify QSF as the ground state in a considerable parameter regime of mass imbalance and 2D coupling strength. Its unique high-order correlation can be manifested in the momentum-space crystallization of a pairing field and density distribution of heavy fermions. Our results can be readily detected in Fermi-Fermi mixtures nowadays realized in cold atoms laboratories, and meanwhile shed light on exotic superfluidity in a broad context of mass-imbalanced fermion mixtures.
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Affiliation(s)
- Ruijin Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Wei Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiaoling Cui
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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2
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Ravensbergen C, Soave E, Corre V, Kreyer M, Huang B, Kirilov E, Grimm R. Resonantly Interacting Fermi-Fermi Mixture of ^{161}Dy and ^{40}K. PHYSICAL REVIEW LETTERS 2020; 124:203402. [PMID: 32501049 DOI: 10.1103/physrevlett.124.203402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 03/12/2020] [Accepted: 05/04/2020] [Indexed: 06/11/2023]
Abstract
We report on the realization of a Fermi-Fermi mixture of ultracold atoms that combines mass imbalance, tunability, and collisional stability. In an optically trapped sample of ^{161}Dy and ^{40}K, we identify a broad Feshbach resonance centered at a magnetic field of 217 G. Hydrodynamic expansion profiles in the resonant interaction regime reveal a bimodal behavior resulting from mass imbalance. Lifetime studies on resonance show a suppression of inelastic few-body processes by orders of magnitude, which we interpret as a consequence of the fermionic nature of our system. The resonant mixture opens up intriguing perspectives for studies on novel states of strongly correlated fermions with mass imbalance.
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Affiliation(s)
- C Ravensbergen
- Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria
- Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria
| | - E Soave
- Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria
| | - V Corre
- Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria
- Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria
| | - M Kreyer
- Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria
| | - B Huang
- Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria
- Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria
| | - E Kirilov
- Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria
| | - R Grimm
- Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria
- Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria
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3
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Ravensbergen C, Corre V, Soave E, Kreyer M, Tzanova S, Kirilov E, Grimm R. Accurate Determination of the Dynamical Polarizability of Dysprosium. PHYSICAL REVIEW LETTERS 2018; 120:223001. [PMID: 29906178 DOI: 10.1103/physrevlett.120.223001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Indexed: 06/08/2023]
Abstract
We report a measurement of the dynamical polarizability of dysprosium atoms in their electronic ground state at the optical wavelength of 1064 nm, which is of particular interest for laser trapping experiments. Our method is based on collective oscillations in an optical dipole trap, and reaches unprecedented accuracy and precision by comparison with an alkali atom (potassium) as a reference species. We obtain values of 184.4(2.4) and 1.7(6) a.u. for the scalar and tensor polarizability, respectively. Our experiments have reached a level that permits meaningful tests of current theoretical descriptions and provides valuable information for future experiments utilizing the intriguing properties of heavy lanthanide atoms.
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Affiliation(s)
- C Ravensbergen
- Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria
- Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria
| | - V Corre
- Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria
- Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria
| | - E Soave
- Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria
| | - M Kreyer
- Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria
- Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria
| | - S Tzanova
- Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria
- Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria
| | - E Kirilov
- Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria
| | - R Grimm
- Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria
- Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria
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Braun J, Drut JE, Roscher D. Zero-temperature equation of state of mass-imbalanced resonant Fermi gases. PHYSICAL REVIEW LETTERS 2015; 114:050404. [PMID: 25699425 DOI: 10.1103/physrevlett.114.050404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Indexed: 06/04/2023]
Abstract
We calculate the zero-temperature equation of state of mass-imbalanced resonant Fermi gases in an ab initio fashion, by implementing the recent proposal of imaginary-valued mass difference to bypass the sign problem in lattice Monte Carlo calculations. The fully nonperturbative results thus obtained are analytically continued to real mass-imbalance to yield the physical equation of state, providing predictions for upcoming experiments with mass-imbalanced atomic Fermi gases. In addition, we present an exact relation for the rate of change of the equation of state at small mass imbalances, showing that it is fully determined by the energy of the mass-balanced system.
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Affiliation(s)
- Jens Braun
- Institut für Kernphysik (Theoriezentrum), Technische Universität Darmstadt, D-64289 Darmstadt, Germany and ExtreMe Matter Institute EMMI, GSI, Planckstraße 1, D-64291 Darmstadt, Germany
| | - Joaquín E Drut
- Institut für Kernphysik (Theoriezentrum), Technische Universität Darmstadt, D-64289 Darmstadt, Germany and ExtreMe Matter Institute EMMI, GSI, Planckstraße 1, D-64291 Darmstadt, Germany and Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - Dietrich Roscher
- Institut für Kernphysik (Theoriezentrum), Technische Universität Darmstadt, D-64289 Darmstadt, Germany
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Jag M, Zaccanti M, Cetina M, Lous RS, Schreck F, Grimm R, Petrov DS, Levinsen J. Observation of a strong atom-dimer attraction in a mass-imbalanced Fermi-Fermi mixture. PHYSICAL REVIEW LETTERS 2014; 112:075302. [PMID: 24579609 DOI: 10.1103/physrevlett.112.075302] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2013] [Indexed: 06/03/2023]
Abstract
We investigate a mixture of ultracold fermionic K40 atoms and weakly bound Li6K40 dimers on the repulsive side of a heteronuclear atomic Feshbach resonance. By radio-frequency spectroscopy we demonstrate that the normally repulsive atom-dimer interaction is turned into a strong attraction. The phenomenon can be understood as a three-body effect in which two heavy K40 fermions exchange the light Li6 atom, leading to attraction in odd partial-wave channels (mainly p wave). Our observations show that mass imbalance in a fermionic system can profoundly change the character of interactions as compared to the well-established mass-balanced case.
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Affiliation(s)
- Michael Jag
- Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria and Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria
| | - Matteo Zaccanti
- Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria and CNR Istituto Nazionale Ottica, 50019 Sesto Fiorentino, Italy
| | - Marko Cetina
- Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria
| | - Rianne S Lous
- Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria and Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria
| | - Florian Schreck
- Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria
| | - Rudolf Grimm
- Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria and Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria
| | - Dmitry S Petrov
- Université Paris-Sud, CNRS, LPTMS, UMR8626, Orsay F-91405, France
| | - Jesper Levinsen
- TCM group, Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom and Aarhus Institute of Advanced Studies, Aarhus University, DK-8000 Aarhus C, Denmark
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6
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Kohstall C, Zaccanti M, Jag M, Trenkwalder A, Massignan P, Bruun GM, Schreck F, Grimm R. Metastability and coherence of repulsive polarons in a strongly interacting Fermi mixture. Nature 2012; 485:615-8. [DOI: 10.1038/nature11065] [Citation(s) in RCA: 330] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2011] [Accepted: 03/09/2012] [Indexed: 11/09/2022]
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Blume D. Few-body physics with ultracold atomic and molecular systems in traps. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2012; 75:046401. [PMID: 22790507 DOI: 10.1088/0034-4885/75/4/046401] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Few-body physics has played a prominent role in atomic, molecular and nuclear physics since the early days of quantum mechanics. It is now possible-thanks to tremendous progress in cooling, trapping and manipulating ultracold samples-to experimentally study few-body phenomena in trapped atomic and molecular systems with unprecedented control. This review summarizes recent studies of few-body phenomena in trapped atomic and molecular gases, with an emphasis on small trapped systems. We start by introducing the free-space scattering properties and then investigate what happens when two particles, bosons or fermions, are placed in an external confinement. Next, various three-body systems are treated analytically in limiting cases. Our current understanding of larger two-component Fermi systems and Bose systems is reviewed, and connections with the corresponding bulk systems are established. Lastly, future prospects and challenges are discussed. Throughout this review, commonalities with other systems such as nuclei or quantum dots are highlighted.
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Affiliation(s)
- D Blume
- Department of Physics and Astronomy, Washington State University, Pullman, WA 99164-2814, USA
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8
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The Unitary Gas and its Symmetry Properties. THE BCS-BEC CROSSOVER AND THE UNITARY FERMI GAS 2012. [DOI: 10.1007/978-3-642-21978-8_5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
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9
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Forbes MM, Gandolfi S, Gezerlis A. Resonantly interacting fermions in a box. PHYSICAL REVIEW LETTERS 2011; 106:235303. [PMID: 21770516 DOI: 10.1103/physrevlett.106.235303] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Revised: 04/06/2011] [Indexed: 05/31/2023]
Abstract
We use two fundamental theoretical frameworks to study the finite-size (shell) properties of the unitary gas in a periodic box: (1) an ab initio quantum Monte Carlo (QMC) calculation for boxes containing 4 to 130 particles provides a precise and complete characterization of the finite-size behavior, and (2) a new density functional theory (DFT) fully encapsulates these effects. The DFT predicts vanishing shell structure for systems comprising more than 50 particles, and allows us to extrapolate the QMC results to the thermodynamic limit, providing the tightest bound to date on the ground-state energy of the unitary gas: ξ(S)≤0.383(1). We also apply the new functional to few-particle harmonically trapped systems, comparing with previous calculations.
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Affiliation(s)
- Michael McNeil Forbes
- Institute for Nuclear Theory, University of Washington, Seattle, Washington 98195-1560, USA
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10
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Mathy CJM, Parish MM, Huse DA. Trimers, molecules, and polarons in mass-imbalanced atomic Fermi gases. PHYSICAL REVIEW LETTERS 2011; 106:166404. [PMID: 21599393 DOI: 10.1103/physrevlett.106.166404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2010] [Indexed: 05/30/2023]
Abstract
We consider the ground state of a single "spin-down" impurity atom interacting attractively with a "spin-up" atomic Fermi gas. By constructing variational wave functions for polarons, molecules, and trimers, we perform a detailed study of the transitions between these dressed bound states as a function of mass ratio r=m↑/m↓ and interaction strength. Crucially, we find that the presence of a Fermi sea enhances the stability of the p-wave trimer, which can be viewed as a Fulde-Ferrell-Larkin-Ovchinnikov molecule that has bound an additional majority atom. For sufficiently large r, we find that the transitions lie outside the region of phase separation of the imbalanced Fermi gas and should thus be observable in experiment, unlike the well-studied equal-mass case.
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Affiliation(s)
- Charles J M Mathy
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
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11
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Ivanov VV, Khramov A, Hansen AH, Dowd WH, Münchow F, Jamison AO, Gupta S. Sympathetic cooling in an optically trapped mixture of alkali and spin-singlet atoms. PHYSICAL REVIEW LETTERS 2011; 106:153201. [PMID: 21568554 DOI: 10.1103/physrevlett.106.153201] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2011] [Indexed: 05/30/2023]
Abstract
We report on the realization of a stable mixture of ultracold lithium and ytterbium atoms confined in a far-off-resonance optical dipole trap. We observe sympathetic cooling of 6Li by 174Yb and extract the s-wave scattering length magnitude |a(6Li-174Yb)|=(13±3)a0 from the rate of interspecies thermalization. Using forced evaporative cooling of 174Yb, we achieve reduction of the 6Li temperature to below the Fermi temperature, purely through interspecies sympathetic cooling.
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Affiliation(s)
- Vladyslav V Ivanov
- Department of Physics, University of Washington, Seattle, Washington 98195, USA
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12
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Trenkwalder A, Kohstall C, Zaccanti M, Naik D, Sidorov AI, Schreck F, Grimm R. Hydrodynamic expansion of a strongly interacting fermi-fermi mixture. PHYSICAL REVIEW LETTERS 2011; 106:115304. [PMID: 21469874 DOI: 10.1103/physrevlett.106.115304] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Revised: 01/13/2011] [Indexed: 05/30/2023]
Abstract
We report on the expansion of an ultracold Fermi-Fermi mixture of (6)Li and (40)K under conditions of strong interactions controlled via an interspecies Feshbach resonance. We study the expansion of the mixture after release from the trap and, in a narrow magnetic-field range, we observe two phenomena related to hydrodynamic behavior. The common inversion of the aspect ratio is found to be accompanied by a collective effect where both species stick together and expand jointly despite of their widely different masses. Our work constitutes a major experimental step for a controlled investigation of the many-body physics of this novel strongly interacting quantum system.
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Affiliation(s)
- A Trenkwalder
- Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria
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13
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Blume D, Daily KM. Breakdown of universality for unequal-mass Fermi gases with infinite scattering length. PHYSICAL REVIEW LETTERS 2010; 105:170403. [PMID: 21231026 DOI: 10.1103/physrevlett.105.170403] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Indexed: 05/30/2023]
Abstract
We treat small trapped unequal-mass two-component Fermi gases at unitarity within a nonperturbative microscopic framework and investigate the system properties as functions of the mass ratio κ, and the numbers N1 and N2 of heavy and light fermions. While equal-mass Fermi gases with infinitely large interspecies s-wave scattering length a(s) are universal, we find that unequal-mass Fermi gases are, for sufficiently large κ and in the regime where Efimov physics is absent, not universal. In particular, the (N₁,N₂) = (2, 1) and (3, 1) systems exhibit three-body and four-body resonances at κ=12.314(2) and 10.4(2), respectively, as well as surprisingly large finite-range effects. These findings have profound implications for ongoing experimental efforts and quantum simulation proposals that utilize unequal-mass atomic Fermi gases.
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Affiliation(s)
- D Blume
- Department of Physics and Astronomy, Washington State University, Pullman, 99164-2814, USA
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Gubbels KB, Baarsma JE, Stoof HTC. Lifshitz point in the phase diagram of resonantly interacting 6Li-40K mixtures. PHYSICAL REVIEW LETTERS 2009; 103:195301. [PMID: 20365934 DOI: 10.1103/physrevlett.103.195301] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2009] [Revised: 10/16/2009] [Indexed: 05/29/2023]
Abstract
We consider a strongly interacting 6Li-40K mixture, which is imbalanced both in the masses and the densities of the two fermionic species. At present, it is the experimentalist's favorite for reaching the superfluid regime. We construct an effective thermodynamic potential that leads to excellent agreement with Monte Carlo results for the normal state. We use it to determine the universal phase diagram of the mixture in the unitarity limit, where we find, in contrast to the mass-balanced case, the presence of a Lifshitz point. This point is characterized by the effective mass of the Cooper pairs becoming negative, which signals an instability towards a supersolid phase.
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Affiliation(s)
- K B Gubbels
- Institute for Theoretical Physics, Utrecht University, Leuvenlaan 4, 3584 CE Utrecht, The Netherlands.
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