Inducing spin-dependent tunneling to probe magnetic correlations in optical lattices

We suggest a simple experimental method for probing antiferromagnetic spin correlations of two-component Fermi gases in optical lattices. The method relies on a spin selective Raman transition to excite atoms of one spin species to their first excited vibrational mode where the tunneling is large. The resulting difference in the tunneling dynamics of the two spin species can then be exploited, to reveal the spin correlations by measuring the number of doubly occupied lattice sites at a later time. We perform quantum Monte Carlo simulations of the spin system and solve the optical lattice dynamics numerically to show how the timed probe can be used to identify antiferromagnetic spin correlations in optical lattices.Comment: 5 pages, 5 figure

Ideal Gases in Time-Dependent Traps

We investigate theoretically the properties of an ideal trapped gas in a time-dependent harmonic potential. Using a scaling formalism, we are able to present simple analytical results for two important classes of experiments: free expansion of the gas upon release of the trap; and the response of the gas to a harmonic modulation of the trapping potential is investigated. We present specific results relevant to current experiments on trapped Fermions.Comment: 5 pages, 3 eps figure

Antiferromagnetic noise correlations in optical lattices

We analyze how noise correlations probed by time-of-flight (TOF) experiments reveal antiferromagnetic (AF) correlations of fermionic atoms in two-dimensional (2D) and three-dimensional (3D) optical lattices. Combining analytical and quantum Monte Carlo (QMC) calculations using experimentally realistic parameters, we show that AF correlations can be detected for temperatures above and below the critical temperature for AF ordering. It is demonstrated that spin-resolved noise correlations yield important information about the spin ordering. Finally, we show how to extract the spin correlation length and the related critical exponent of the AF transition from the noise.Comment: 4 pages, 4 figure

De gjorde en forskel. Om 30 personer der i årene 1990- 2005 medvirkede afgørende til at give Aarhus By et erhvervsmæssigt løft

Artiklens forfatter var i femten år (1990- 2005) chef for Aarhus Kommunes erhvervsafdeling (Director of Business Development, Municipality of Aarhus). Erhvervsafdeling havde på embedsmandsplan ansvaret for at udarbejde og implementere kommunens erhvervsfremme aktiviteter. Det er oplevelserne fra dette samspil med personer fra byens erhvervsliv og erhvervsrelevante organisationer og institutioner, der er beskrevet i artiklen. Den opnåede personlige indsigt og en efterfølgende research peger nu på 30 personer som i perioden havde en særlig indflydelse på byens erhvervsudvikling. Artiklen forsøger at sandsynliggøre, at Aarhus bys erhvervsudvikling i perioden 1990-2005 blev afgørende præget af disse 30 navngivne passionate individuals. Uden disse personers indsats er hypotesen, at byens erhvervsudvikling målt i den skabte beskæftigelse ville have nærmet sig landsgennemsnittet, hvor den nu lå 10 % over og samtidig klart over udviklingen i de andre danske storbyer. Antal og kvalitet af et områdes passionerede individer er altså vigtig, og man kan som nære bekymring for effekten af vor tids fremvoksende snævre egoistiske tankesæt

Laser probing of Cooper-paired trapped atoms

We consider a gas of trapped Cooper-paired fermionic atoms which are manipulated by laser light. The laser induces a transition from an internal state with large negative scattering length (superfluid) to one with weaker interactions (normal gas). We show that the process can be used to detect the presence of the superconducting order parameter. Also, we propose a direct way of measuring the size of the gap in the trap. The efficiency and feasibility of this probing method is investigated in detail in different physical situations.Comment: 9 pages, 8 figure

Cooper-pair coherence in a superfluid Fermi-gas of atoms

We study the coherence properties of a trapped two-component gas of fermionic atoms below the BCS critical temperature. We propose an optical method to investigate the Cooper-pair coherence across different regions of the superfluid. Near-resonant laser light is used to induce transitions between the two coupled hyperfine states. The beam is split so that it probes two spatially separate regions of the gas. Absorption of the light in this interferometric scheme depends on the Cooper-pair coherence between the two regions.Comment: 10 pages, 5 figures. Submitted to J. Phys. B as a proceedings of the Salerno 2001 BEC worksho

Measuring spin correlations in optical lattices using superlattice potentials

We suggest two experimental methods for probing both short- and long-range spin correlations of atoms in optical lattices using superlattice potentials. The first method involves an adiabatic doubling of the periodicity of the underlying lattice to probe neighboring singlet (triplet) correlations for fermions (bosons) by the occupation of the new vibrational ground state. The second method utilizes a time-dependent superlattice potential to generate spin-dependent transport by any number of prescribed lattice sites, and probes correlations by the resulting number of doubly occupied sites. For experimentally relevant parameters, we demonstrate how both methods yield large signatures of antiferromagnetic (AF) correlations of strongly repulsive fermionic atoms in a single shot of the experiment. Lastly, we show how this method may also be applied to probe d-wave pairing, a possible ground state candidate for the doped repulsive Hubbard model.Comment: 5 pages, 3 figure

Signatures of Superfluidity in Dilute Fermi Gases near a Feshbach Resonance

We present a brief account of the most salient properties of vortices in dilute atomic Fermi superfluids near a Feshbach resonance.Comment: 6 pages, 1 figure, and jltp.cls. Several typos and a couple of inaccuracies have been correcte