arXiv:cond-mat/0606757 · Physical Review A

Control of the interaction in a Fermi-Bose mixture

Matteo Zaccanti, Chiara D’Errico, Francesca Ferlaino, G. Roati, M. Inguscio, Giovanni Carlo Modugno

Published Oct 26, 2006• 122 citations

Abstract

We control the interspecies interaction in a two-species atomic quantum mixture by tuning the magnetic field at a Feshbach resonance. The mixture is composed by fermionic $^{40}\mathrm{K}$ and bosonic $^{87}\mathrm{Rb}$. We observe effects of the large attractive and repulsive interaction energy across the resonance, such as collapse or a reduced spatial overlap of the mixture, and we accurately locate the resonance position and width. Understanding and controlling instabilities in this mixture opens the way to a variety of applications, including formation of heteronuclear molecular quantum gases.

DOI: 10.1103/physreva.74.041605

Related papers

Observation of Heteronuclear Feshbach Resonances in a Mixture of Bosons and Fermions

S. Inouye, J. Goldwin, M. L. Olsen +3 more

arXiv:cond-mat/0406208Physical Review LettersOct 25, 2004307 citations

Quantum degenerate Fermi and Bose gases

Ch Salomon, Thomas Bourdel, J. Cubizolles +3 more

European Quantum Electronics Conference (EQEC)Jan 1, 20030 citations

Fermionic quantum mixtures with tunable interactions

Rudolf Grimm, Cosetta Baroni

arXiv:2311.01220Nov 2, 20230 citations

Fermi-Bose mixture across a Feshbach resonance

Luca Salasnich, Flavio Toigo

arXiv:cond-mat/0701098Physical Review AJan 25, 200722 citations

Tuning of Heteronuclear Interactions in a Degenerate Fermi-Bose Mixture

Silke Ospelkaus, C. Ospelkaus, Leif Humbert +2 more

arXiv:cond-mat/0607091Physical Review LettersSep 18, 2006166 citations

Phase separation and collapse in Bose-Fermi mixtures with a Feshbach resonance

Francesca Maria Marchetti, Charles Mathy, David A. Huse +1 more

arXiv:0801.0635Physical Review BOct 14, 200851 citations

arXiv:cond-mat/0606757 · Physical Review A

Control of the interaction in a Fermi-Bose mixture

Matteo Zaccanti, Chiara D’Errico, Francesca Ferlaino, G. Roati, M. Inguscio, Giovanni Carlo Modugno

Published Oct 26, 2006• 122 citations

arXiv HTML PDF

Abstract

We control the interspecies interaction in a two-species atomic quantum mixture by tuning the magnetic field at a Feshbach resonance. The mixture is composed by fermionic

^{40}\mathrm{K}

and bosonic

^{87}\mathrm{Rb}

. We observe effects of the large attractive and repulsive interaction energy across the resonance, such as collapse or a reduced spatial overlap of the mixture, and we accurately locate the resonance position and width. Understanding and controlling instabilities in this mixture opens the way to a variety of applications, including formation of heteronuclear molecular quantum gases.

DOI: 10.1103/physreva.74.041605

Related papers

Observation of Heteronuclear Feshbach Resonances in a Mixture of Bosons and Fermions

S. Inouye, J. Goldwin, M. L. Olsen +3 more

Three magnetic-field induced heteronuclear Feshbach resonances were identified in collisions between bosonic $^{87}\mathrm{R}\mathrm{b}$ and fermionic $^{40}\mathrm{K}$ atoms in their absolute ground states. Strong inelastic loss from an optically trapped mixture was observed at the resonance positions of 492, 512, and $543\ifmmode\pm\else\textpm\fi{}2\text{ }\text{ }\mathrm{G}$. The magnetic-field locations of these resonances place a tight constraint on the triplet and singlet cross-species scattering lengths, yielding $(\ensuremath{-}281\ifmmode\pm\else\textpm\fi{}15){a}_{0}$ and $(\ensuremath{-}54\ifmmode\pm\else\textpm\fi{}12){a}_{0}$, respectively. The width of the loss feature at 543 G is $3.7\ifmmode\pm\else\textpm\fi{}1.5\text{ }\text{ }\mathrm{G}$ wide; this broad Feshbach resonance should enable experimental control of the interspecies interactions.Three magnetic-field induced heteronuclear Feshbach resonances were identified in collisions between bosonic $^{87}\mathrm{R}\mathrm{b}$ and fermionic $^{40}\mathrm{K}$ atoms in their absolute ground states. Strong inelastic loss from an optically trapped mixture was observed at the resonance positions of 492, 512, and $543\ifmmode\pm\else\textpm\fi{}2\text{ }\text{ }\mathrm{G}$. The magnetic-field locations of these resonances place a tight constraint on the triplet and singlet cross-species scattering lengths, yielding $(\ensuremath{-}281\ifmmode\pm\else\textpm\fi{}15){a}_{0}$ and $(\ensuremath{-}54\ifmmode\pm\else\textpm\fi{}12){a}_{0}$, respectively. The width of the loss feature at 543 G is $3.7\ifmmode\pm\else\textpm\fi{}1.5\text{ }\text{ }\mathrm{G}$ wide; this broad Feshbach resonance should enable experimental control of the interspecies interactions.

arXiv:cond-mat/0406208Physical Review LettersOct 25, 2004307 citations

Quantum degenerate Fermi and Bose gases

Ch Salomon, Thomas Bourdel, J. Cubizolles +3 more

Recent experiments performed with fermionic /sup 6/Li and /sup 40/K atoms, which possess both Feshbach resonances at convenient magnetic fields are discussed. When /sup 40/K is mixed with a Bose-Einstein condensate of /sup 87/Rb, for sufficient atom numbers of both species, a collapse of the Fermi gas is observed. This is the result of the strong interspecies attractive interaction which overcomes the Fermi pressure in the quantum degenerate regime. As for the case of phonon-induced interaction between electrons in superconductors, it is predicted that the boson-fermion attractive interaction favors Cooper pairing of fermions when prepared in a mixture of two states.Recent experiments performed with fermionic /sup 6/Li and /sup 40/K atoms, which possess both Feshbach resonances at convenient magnetic fields are discussed. When /sup 40/K is mixed with a Bose-Einstein condensate of /sup 87/Rb, for sufficient atom numbers of both species, a collapse of the Fermi gas is observed. This is the result of the strong interspecies attractive interaction which overcomes the Fermi pressure in the quantum degenerate regime. As for the case of phonon-induced interaction between electrons in superconductors, it is predicted that the boson-fermion attractive interaction favors Cooper pairing of fermions when prepared in a mixture of two states.

European Quantum Electronics Conference (EQEC)Jan 1, 20030 citations

Fermionic quantum mixtures with tunable interactions

Rudolf Grimm, Cosetta Baroni

The topic of the present lecture notes are two-species quantum mixtures composed of a deeply degenerate Fermi gas and a second component, the latter being fermionic or bosonic. A key ingredient is the possibility to tune the $s$ -wave interaction between the different species by means of magnetically controlled Feshbach resonances, which allow us to investigate regimes of strong interactions. In two case studies, we review our experiments on mixtures of $^6$ Li fermions with fermionic $^{40}$ K or bosonic $^{41}$ K atoms and on mixtures of fermionic $^{161}$ Dy with $^{40}$ K atoms. We cover various topics of fermionic quantum many-body physics, ranging from impurity physics and quasiparticles over phase separation to the formation of ultracold molecules and progress towards novel superfluids.The topic of the present lecture notes are two-species quantum mixtures composed of a deeply degenerate Fermi gas and a second component, the latter being fermionic or bosonic. A key ingredient is the possibility to tune the $s$-wave interaction between the different species by means of magnetically controlled Feshbach resonances, which allow us to investigate regimes of strong interactions. In two case studies, we review our experiments on mixtures of $^6$Li fermions with fermionic $^{40}$K or bosonic $^{41}$K atoms and on mixtures of fermionic $^{161}$Dy with $^{40}$K atoms. We cover various topics of fermionic quantum many-body physics, ranging from impurity physics and quasiparticles over phase separation to the formation of ultracold molecules and progress towards novel superfluids.

arXiv:2311.01220Nov 2, 20230 citations

Fermi-Bose mixture across a Feshbach resonance

Luca Salasnich, Flavio Toigo

We study a dilute mixture of degenerate bosons and fermions across a Feshbach resonance of the Fermi-Fermi scattering length ${a}_{F}$ . This scattering length is renormalized by the boson-induced interaction between fermions and its value is crucial to determine the phase diagram of the system. For the mixture in a box and a positive Bose-Fermi scattering length, we show that there are three possibilities: A single uniform mixed phase, a purely fermionic phase coexisting with a mixed phase, and a purely fermionic phase coexisting with a purely bosonic one. As $1∕{a}_{F}$ is increased from a negative value to the Feshbach resonance $(1∕{a}_{F}=0)$ , the region of pure separation increases and the other two regions are strongly reduced. Above the Feshbach resonance $(1∕{a}_{F}>0)$ , pairs of Fermi atoms become Bose-condensed molecules. We find that these molecules are fully spatially separated from the bosonic atoms when $1∕{a}_{F}$ exceeds a critical value. For a negative Bose-Fermi scattering length we deduce the condition for collapse, which coincides with the onset of dynamical instability of the fully mixed phase. We consider also the mixture in a harmonic trap and determine the conditions for partial demixing, full demixing, and collapse. The experimental implications of our results are investigated by analyzing mixtures of $^{6}\mathrm{Li}\text{\ensuremath{-}}^{23}\mathrm{Na}$ and $^{40}\mathrm{K}\text{\ensuremath{-}}^{87}\mathrm{Rb}$ atoms.We study a dilute mixture of degenerate bosons and fermions across a Feshbach resonance of the Fermi-Fermi scattering length ${a}_{F}$. This scattering length is renormalized by the boson-induced interaction between fermions and its value is crucial to determine the phase diagram of the system. For the mixture in a box and a positive Bose-Fermi scattering length, we show that there are three possibilities: A single uniform mixed phase, a purely fermionic phase coexisting with a mixed phase, and a purely fermionic phase coexisting with a purely bosonic one. As $1∕{a}_{F}$ is increased from a negative value to the Feshbach resonance $(1∕{a}_{F}=0)$, the region of pure separation increases and the other two regions are strongly reduced. Above the Feshbach resonance $(1∕{a}_{F}>0)$, pairs of Fermi atoms become Bose-condensed molecules. We find that these molecules are fully spatially separated from the bosonic atoms when $1∕{a}_{F}$ exceeds a critical value. For a negative Bose-Fermi scattering length we deduce the condition for collapse, which coincides with the onset of dynamical instability of the fully mixed phase. We consider also the mixture in a harmonic trap and determine the conditions for partial demixing, full demixing, and collapse. The experimental implications of our results are investigated by analyzing mixtures of $^{6}\mathrm{Li}\text{\ensuremath{-}}^{23}\mathrm{Na}$ and $^{40}\mathrm{K}\text{\ensuremath{-}}^{87}\mathrm{Rb}$ atoms.

arXiv:cond-mat/0701098Physical Review AJan 25, 200722 citations

Tuning of Heteronuclear Interactions in a Degenerate Fermi-Bose Mixture

Silke Ospelkaus, C. Ospelkaus, Leif Humbert +2 more

We demonstrate tuning of interactions between fermionic 40K and bosonic 87Rb atoms by Feshbach resonances and access the complete phase diagram of the harmonically trapped mixture from phase separation to collapse. On the attractive side of the resonance, we observe a strongly enhanced mean-field energy of the condensate due to the mutual mean-field confinement, predicted by a Thomas-Fermi model. As we increase heteronuclear interactions beyond a threshold, we observe an induced collapse of the mixture. On the repulsive side of the resonance, we observe vertical phase separation of the mixture in the presence of the gravitational force, thus entering a completely unexplored part of the phase diagram of the mixture. In addition, we identify the 515 G resonance as p wave by its characteristic doublet structure.We demonstrate tuning of interactions between fermionic 40K and bosonic 87Rb atoms by Feshbach resonances and access the complete phase diagram of the harmonically trapped mixture from phase separation to collapse. On the attractive side of the resonance, we observe a strongly enhanced mean-field energy of the condensate due to the mutual mean-field confinement, predicted by a Thomas-Fermi model. As we increase heteronuclear interactions beyond a threshold, we observe an induced collapse of the mixture. On the repulsive side of the resonance, we observe vertical phase separation of the mixture in the presence of the gravitational force, thus entering a completely unexplored part of the phase diagram of the mixture. In addition, we identify the 515 G resonance as p wave by its characteristic doublet structure.

arXiv:cond-mat/0607091Physical Review LettersSep 18, 2006166 citations

Phase separation and collapse in Bose-Fermi mixtures with a Feshbach resonance

Francesca Maria Marchetti, Charles Mathy, David A. Huse +1 more

We consider a mixture of single-component bosonic and fermionic atoms with an interspecies interaction that is varied using a Feshbach resonance. By performing a mean-field analysis of a two-channel model, which describes both narrow and broad Feshbach resonances, we find an unexpectedly rich phase diagram at zero temperature: Bose-condensed and non-Bose-condensed phases form a variety of phase-separated states that are accompanied by both critical and tricritical points. We discuss the implications of our results for the experimentally observed collapse of Bose-Fermi mixtures on the attractive side of the Feshbach resonance, and we make predictions for future experiments on Bose-Fermi mixtures close to a Feshbach resonance.We consider a mixture of single-component bosonic and fermionic atoms with an interspecies interaction that is varied using a Feshbach resonance. By performing a mean-field analysis of a two-channel model, which describes both narrow and broad Feshbach resonances, we find an unexpectedly rich phase diagram at zero temperature: Bose-condensed and non-Bose-condensed phases form a variety of phase-separated states that are accompanied by both critical and tricritical points. We discuss the implications of our results for the experimentally observed collapse of Bose-Fermi mixtures on the attractive side of the Feshbach resonance, and we make predictions for future experiments on Bose-Fermi mixtures close to a Feshbach resonance.

arXiv:0801.0635Physical Review BOct 14, 200851 citations

We control the interspecies interaction in a two-species atomic quantum mixture by tuning the magnetic field at a Feshbach resonance. The mixture is composed by fermionic

^{40}\mathrm{K}

and bosonic

^{87}\mathrm{Rb}

Three magnetic-field induced heteronuclear Feshbach resonances were identified in collisions between bosonic

^{87}\mathrm{R}\mathrm{b}

and fermionic

^{40}\mathrm{K}

atoms in their absolute ground states. Strong inelastic loss from an optically trapped mixture was observed at the resonance positions of 492, 512, and $543\ifmmode\pm\else\textpm\fi{}2\text{ }\text{ }\mathrm{G}$. The magnetic-field locations of these resonances place a tight constraint on the triplet and singlet cross-species scattering lengths, yielding $(\ensuremath{-}281\ifmmode\pm\else\textpm\fi{}15){a}_{0}$ and $(\ensuremath{-}54\ifmmode\pm\else\textpm\fi{}12){a}_{0}$, respectively. The width of the loss feature at 543 G is $3.7\ifmmode\pm\else\textpm\fi{}1.5\text{ }\text{ }\mathrm{G}$ wide; this broad Feshbach resonance should enable experimental control of the interspecies interactions.

s

-wave interaction between the different species by means of magnetically controlled Feshbach resonances, which allow us to investigate regimes of strong interactions. In two case studies, we review our experiments on mixtures of

^6

Li fermions with fermionic

^{40}

K or bosonic

^{41}

K atoms and on mixtures of fermionic

^{161}

Dy with

^{40}

K atoms. We cover various topics of fermionic quantum many-body physics, ranging from impurity physics and quasiparticles over phase separation to the formation of ultracold molecules and progress towards novel superfluids.

We study a dilute mixture of degenerate bosons and fermions across a Feshbach resonance of the Fermi-Fermi scattering length

{a}_{F}

. This scattering length is renormalized by the boson-induced interaction between fermions and its value is crucial to determine the phase diagram of the system. For the mixture in a box and a positive Bose-Fermi scattering length, we show that there are three possibilities: A single uniform mixed phase, a purely fermionic phase coexisting with a mixed phase, and a purely fermionic phase coexisting with a purely bosonic one. As

1∕{a}_{F}

is increased from a negative value to the Feshbach resonance

(1∕{a}_{F}=0)

, the region of pure separation increases and the other two regions are strongly reduced. Above the Feshbach resonance

(1∕{a}_{F}>0)

, pairs of Fermi atoms become Bose-condensed molecules. We find that these molecules are fully spatially separated from the bosonic atoms when

1∕{a}_{F}

exceeds a critical value. For a negative Bose-Fermi scattering length we deduce the condition for collapse, which coincides with the onset of dynamical instability of the fully mixed phase. We consider also the mixture in a harmonic trap and determine the conditions for partial demixing, full demixing, and collapse. The experimental implications of our results are investigated by analyzing mixtures of $^{6}\mathrm{Li}\text{\ensuremath{-}}^{23}\mathrm{Na}$ and $^{40}\mathrm{K}\text{\ensuremath{-}}^{87}\mathrm{Rb}$ atoms.