Sound propagation in a fermi gas near a feshbach resonance j. May 6, 2004 abstract at low temperature, fermionic atoms can either condense into a boseeinstein condensate bec. Permission is granted to copy, distribute andor modify this document under the terms of the gnu free documentation license, version 1. Feshbach resonances, this is not the case for alkalineearth. In physics, a feshbach resonance can occur upon collision of two slow atoms, when they temporarily stick together forming an unstable compound with short lifetime socalled resonance. However, more generally any autoionizing state generated by removing an innershell electron is a feshbach resonance, and therefore these states underlie auger, costerkronig, or icd decay. In addition, in case of onephoton resonance the lower vibrational molecular state is coupled by laser radiation with the continuum of the elastic channel and forms laserinduced feshbach resonance via both autlertownes effect and lics mechanism.
Thus, an atomic cloud which would not condense in the absence of a magnetic. A copy of the license is included in the section entitled gnu free documentation license. Pdf we probe swave collisions of lasercooled 85rb\ f 2,mf 2\ atoms with zeemanresolved photoassociation spectroscopy. Pairing is a process that is competing with the stoner instability and it would be nice to show that stoner wins in some regimes. Direct observation of resonant scattering phase shifts and. Magnetization dynamics for noninteracting particles. A feshbach resonance also produces a dramatic change in the scattering length, the parameter that characterizes the interatomic interaction strength within the condensate. Typical lifetimes for excited molecular states are on the order of 10ns which corresponds to a linewidth of 216mhz. Feshbach resonances were rst applied to tune the interactions between ultracold fermi gases in the late 1990s. Turning now to fermi systems, one of the major steps in the development of the bcs theory of superconductivity was coopers demonstration in 1956 that a fermi gas. Publishers pdf, also known as version of record includes final page, issue and. Feshbach resonance in this context is the interaction of two atoms when, at a particular magnetic b field strength, emmulate a molecule.
In recent years, feshbach resonances have been exploited in ultracold col. Quantum mechanical scattering and feshbach resonance. We consider photoassociation from a state of two free atoms when the continuum state is close to a magnetic field induced feshbach resonance and analyze fano interference in photoassociation. We present a simple onedimensional example of a spin 12 particle submitted to a deltatype potential which interacs differently with the two components of the wavefunction and to an external magnetic field. In comparison to the wellknown magnetic feshbach resonances, these optical feshbach resonances. Influence of external magnetic and laser radiation fields. Pdf observation of a feshbach resonance in cold atom scattering. Similar inelastic collisions occur between clock and target atoms, but because the clock atom density is.
Creating ground state molecules with optical feshbach. Feshbach resonances with large background scattering length. Crossing the feshbach resonance, the scattering length a. In this context, magnetic feshbach resonances frs proved to be a. For lindsay leblanc in josephs lab, started september 2007. They allow us to address key problems in several fields of physics. Lev department of physics, university of illinois at urbanachampaign, urbana, illinois 618080, usa received 9 july 2010. At this frontier of physics, basic questions about the nature of superfluidity, the transition between insulating. Observing the creation of electronic feshbach resonances. We implement the open and the closed channels inside a pair of such arrays, linked by a separated cavity or a tunable qubit. Abm calculated widths of all swave feshbach resonances in stable twocomponent 6li40k mixtures below 500 g.
Inducing an optical feshbach resonance via stimulated. Pdf feshbach resonance induced fano interference in. The crucial difference between a shape resonance and a feshbach resonance is that in the latter case, the molecular state responsible for the resonance has a magnetic moment that is different from the magnetic moment of the colliding atoms 17, 183. In particular, we observed a wellisolated swave resonance in the. The bound state perturbs the scattering state which can, in turn, strongly affect the rate of pa 2. In addition to two previously known swave resonances, we found three pwave resonances. When a single photon is bounded inside the closed channel by setting the relevant physical parameters appropriately, the vanishing transmission appears to. Pdf sound propagation in a fermi gas near a feshbach. Atomic clock measurements of quantum scattering phase. Becbcs crossover with feshbach resonance for three. Feshbach resonances are the essential tool to control the interaction between atoms in ultracold quantum gases. A disadvantage of optically induced feshbach resonance is the inherent loss of atoms due to excitation and spontaneous decay of the molecular state 9. Nowadays, probably feshbachs most widely known contribution to physics is the concept known as feshbach resonance. Feshbach resonance picture was used to describe nuclear collisions.
They have found numerous experimental applications, opening up the way to important breakthroughs. Feshbach resonance is a resonance for twoatom scattering with two or more channels, in which a bound state is achieved in one channel. As a result, we can tune the binary condensate from being miscible to immiscible simply by varying the magnetic. Such a shape resonance occurs when the interatomic. It would be helpful if somebody could answer what they have understood and not just give references. Optical feshbach resonances in a boseeinstein condensate dissertation. The first is that for energies away from the resonance, 0.
Due to the low temperatures of the ultracold gases, their e. How can one physically understand this phenomenon of feshbach resonance. Observation of an orbital interactioninduced feshbach resonance in 173yb. Dysprosium magnetooptical traps seo ho youn, mingwu lu, ushnish ray, and benjamin l. We show that this resonance phenomenon not only exists during the collisions of massive particles, but also emerges. Feshbach resonances in cold atomic gases technische. Inthis chapterwe introducethefeshbachresonances thatare usedtotunethe.
It is now also used in many other creative ways to make atomic systems with interactions to order. Duke university, department of physics, durham, north carolina, 27708, usa dated. In order to obtain a better understanding of the dissociative electron resonance capture processes of h 2 o we have remeasured the ionization efficie the relative intensities of these curves are strongly dependent on the ion focusing conditions. Feshbach resonances in lithium6 were experimentally studied and theoretically analyzed. Feshbachresonances and dissociative electron attachment. Crossover from boseeinstein condensed molecules to. This detuning is related to the heteronuclear scattering length, which is given by a a bg1 w b b 0. Feshbach resonances in ultracold atoms the budker group. Optical feshbach resonances in a boseeinstein condensate. First described by herman feshbach in a 1958 paper, feshbach resonances describe resonant scattering between two particles when their incoming energies are very close to those of a twoparticle bound state. Two broad resonances from coupling between d waves in both the open and closed channels are observed and characterized. Creating ground state molecules with optical feshbach resonances in tight traps christiane p. Observation of broad dwave feshbach resonances with a. Box 5, 5600mb eindhoven, the netherlands received 19 june 2002.
Feshbach resonance engineering is a central tool for producing boseeinstein condensates. Collisional stability of fermionic feshbach molecules. The background scattering length is a bg 185a 0, where a 0 is. In a feshbach resonance, the effective swave scattering length grows when one moves toward the resonance point, and eventually diverges at this point. It is a feature of manybody systems in which a bound state is achieved if the couplings between at least one internal degree of freedom and the reaction coordinates, which lead to dissociation, vanish. We measured 26 not previously observed resonances, 12 swave and 14 pwave resonances. Feshbach resonances in fermionic lithium6 request pdf. A feshbach resonance occurs when the bound molecularstate in closed channel energetically approaches the scattering state in open channel. Is it that one elastic scattering process is mapped to one bound state.
May 15, 2009 first described by herman feshbach in a 1958 paper, feshbach resonances describe resonant scattering between two particles when their incoming energies. Feshbach resonances provide an e cient method to producing ultracold molecules. Order parameters predicted by lax vector analysis in a 1d system. Landauzener transitions and a feshbach resonance in. Feshbach resonances in k antje ludewig homepages of uva. February 4, 2008 sound waves are observed and studied in an optically trapped degenerate fermi gas of spinup and spindown atoms with magnetically tunable interactions. For feshbach molecules, will depend on the magnetic. Analyzing feshbach resonances physikalisches institut. Fanofeshbach resonances in highly magnetic atoms have been observed in chromium. Feshbach resonances with large background scattering. Crossover from boseeinstein condensed molecules to cooper pairs by using feshbach resonance shuwei chang department of electrical and computer engineering, university of illinois at urbanachampaign, urbana, il 61801, usa dated. Note that is project has been superceeded by the feshbachmot coils project. Although feshbach molecules themselves are extremely \fragile, feshbach resonance association is a potentially coherent method that creates molecules in a sin. Near feshbach resonance, a system of two component fermions will form very strongly bound cooper pairs.
Feshbach resonance is realized by tuning a molecular bound state near the scattering threshold 1. The rate of association of a boseeinstein condensate bec is of particular inter. Exploring fewbody scattering resonances in a bosefermi. It has two coupled channels, admits a closed solution and features the feshbach resonance phenomenon by proper tunning of the magnetic field.
B index to important data files 121 c publications 123 bibliography 7. The grosspitaevskii equation for the macroscopically occupied quantum state of each single atom, the condensate wave function. Publishers pdf, also known as version of record includes final page. The rapid phase change is a general feature of resonance phenomena and the resonant energy dependence of cross sections has been. Feshbach resonances and weakly bound molecular states of boson.
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