Publications Marian KREYER

2023

Article

E. Soave, A. Canali, Z. Ye, M. Kreyer, E. Kirilov, R. Grimm Optically trapped Feshbach molecules of fermionic 161Dy and 40K, Phys. Rev. Research 5 33117 (2023-04-17), http://dx.doi.org/10.1103/PhysRevResearch.5.033117 doi:10.1103/PhysRevResearch.5.033117 (ID: 721079) Toggle Abstract
We report on the preparation of a pure ultracold sample of bosonic DyK Feshbach molecules, composed of the fermionic isotopes 161Dy and 40K. By sweeping a magnetic field across a resonance located near 7.3 G, we generate up to 5000 molecules at a temperature of approximately 50 nK. To purify the sample from remaining atoms, we employ a Stern-Gerlach technique that relies on magnetic levitation of the molecules in a very weak optical dipole trap. With the trapped molecules we finally reach a high phase-space density of about 0.1. We investigate the magnetic field dependence of the molecular binding energy and the magnetic moment, refining our knowledge of the resonance parameters. We also demonstrate a peculiar anisotropic expansion effect observed when the molecules are released from the trap and expand freely in the magnetic levitation field. Furthermore, we identify an important lifetime limitation that is imposed by the 1064-nm infrared trap light itself and not by inelastic collisions. The light-induced decay rate is found to be proportional to the trap light intensity and the closed-channel fraction of the Feshbach molecule. These observations suggest a one-photon coupling to electronically excited states to limit the lifetime and point to the prospect of loss suppression by optimizing the wavelength of the trapping light. Our results offer crucial insights and experimental progress towards achieving quantum-degenerate samples of DyK molecules and novel superfluids based on mass-imbalanced fermion mixtures.

Dissertation

M. Kreyer Strongly Interacting Fermi-Fermi Mixtures of Dy and K: Monte Carlo Simulations and Trapping Potential Control, (2023-07-06), (ID: 721108)

2022

Articles

Zhuxiong Ye, Alberto Canali, Elisa Soave, Marian Kreyer, Yaakov Yudkin, Cornelis Ravensbergen, Emil Kirilov, Rudolf Grimm Observation of low-field Feshbach resonances between 161Dy and 40K, Phys. Rev. A 106 PhysRevA.106.043314 (2022-10-17), http://dx.doi.org/10.1103/PhysRevA.106.043314 doi:10.1103/PhysRevA.106.043314 (ID: 720848) Toggle Abstract
We report on the observation of Feshbach resonances at low magnetic field strength (below 10 G) in the Fermi-Fermi mixture of 161Dy and 40K. We characterize five resonances by measurements of interspecies thermalization rates and molecular binding energies. As a case of particular interest for applications, we consider a resonance near 7.29 G, which combines accurate magnetic tunability and access to the universal regime of interactions with experimental simplicity. We show that lifetimes of a few 100 ms can be achieved for the optically trapped, resonantly interacting mixture. We also demonstrate the hydrodynamic expansion of the mixture in the strongly interacting regime and the formation of DyK Feshbach molecules. Our work opens up new experimental possibilities in view of mass-imbalanced superfluids and related phenomena.
Elisa Soave, Vincent Corre, Cornelis Ravensbergen, Jeong Ho Han, Marian Kreyer, Emil Kirilov, Rudolf Grimm Low-field Feshbach resonances and three-body losses in a fermionic quantum gas of 161Dy, Ukr. J. Phys. 67 334 (2022-08-29), http://dx.doi.org/10.15407/ujpe67.5.334 doi:10.15407/ujpe67.5.334 (ID: 720847) Toggle Abstract
We report on high-resolution Feshbach spectroscopy on a degenerate, spin-polarized Fermi gas of 161Dy atoms, measuring three-body recombination losses at low magnetic field. For field strength up to 1\,G, we identify as much as 44 resonance features and observe plateaus of very low losses. For four selected typical resonances, we study the dependence of the three-body recombination rate coefficient on the magnetic resonance detuning and on the temperature. We observe a strong suppression of losses with decreasing temperature already for small detunings from resonance. The characterization of complex behavior of three-body losses of fermionic 161Dy is important for future applications of this peculiar species in research on atomic quantum gases.

2021

Article

M. Kreyer, J. H. Han, C. Ravensbergen, V. Corre, E. Soave, E. Kirilov, R. Grimm Measurement of the dynamic polarizability of Dy atoms near the 626-nm intercombination line, Phys. Rev. A 104 33106 (2021-09-10), http://dx.doi.org/10.1103/PhysRevA.104.033106 doi:10.1103/PhysRevA.104.033106 (ID: 720639) Toggle Abstract
We report on measurements of the anisotropic dynamical polarizability of Dy near the 626-nm intercombination line, employing modulation spectroscopy in a one-dimensional optical lattice. To eliminate large systematic uncertainties resulting from the limited knowledge of the spatial intensity distribution, we use K as a reference species with accurately known polarizability. This method can be applied independently of the sign of the polarizability, i.e. for both attractive and repulsive optical fields on both sides of a resonance. By variation of the laser polarization we extract the scalar and the tensorial part. To characterize the strength of the transition, we also derive the natural linewidth. We find our result in excellent agreement with literature values, which provide a sensitive benchmark for the accuracy of our method. In addition we demonstrate optical dipole trapping on the intercombination line, confirming the expected long lifetimes and low heating rates. This provides an additional tool to tailor optical potentials for Dy atoms and for the species-specific manipulation of atoms in the Dy-K mixture.

2020

Article

C. Ravensbergen, E. Soave, V. Corre, M. Kreyer, B. Huang, E. Kirilov, R. Grimm Resonantly Interacting Fermi-Fermi Mixture of 161Dy and 40K, Phys. Rev. Lett. 124 203402 (2020-05-22), http://dx.doi.org/10.1103/PhysRevLett.124.203402 doi:10.1103/PhysRevLett.124.203402 (ID: 720519)

2018

Articles

C. Ravensbergen, V. Corre, E. Soave, M. Kreyer, E. Kirilov, R. Grimm Production of a degenerate Fermi-Fermi mixture of dysprosium and potassium atoms, Phys. Rev. A 98 63624 (2018-12-20), http://dx.doi.org/10.1103/PhysRevA.98.063624 doi:10.1103/PhysRevA.98.063624 (ID: 720087) Toggle Abstract
We report on the realization of a mixture of fermionic 161^{161}Dy and fermionic 40^{40}K where both species are deep in the quantum-degenerate regime. Both components are spin-polarized in their absolute ground states, and the low temperatures are achieved by means of evaporative cooling of the dipolar dysprosium atoms together with sympathetic cooling of the potassium atoms. We describe the trapping and cooling methods, in particular the final evaporation stage, which leads to Fermi degeneracy of both species. Analyzing cross-species thermalization we obtain an estimate of the magnitude of the inter-species ss-wave scattering length at low magnetic field. We demonstrate magnetic levitation of the mixture as a tool to ensure spatial overlap of the two components. The properties of the Dy-K mixture make it a very promising candidate to explore the physics of strongly interacting mass-imbalanced Fermi-Fermi mixtures.
C. Ravensbergen, V. Corre, E. Soave, M. Kreyer, S. Tzanova, E. Kirilov, R. Grimm Accurate Determination of the Dynamical Polarizability of Dysprosium, Phys. Rev. Lett. 120 223001 (2018-01-18), http://dx.doi.org/10.1103/PhysRevLett.120.223001 doi:10.1103/PhysRevLett.120.223001 (ID: 719964) Toggle 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) a.u. 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 theo- retical descriptions and provides valuable information for future experiments utilizing the intriguing properties of heavy lanthanide atoms.