Publications Emil KIRILOV

2021

Articles

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.
I. Fritsche, C. Baroni, E. Dobler, E. Kirilov, B. Huang, R. Grimm, G. Bruun, P. Massignan Stability and breakdown of Fermi polarons in a strongly interacting Fermi-Bose mixture, Phys. Rev. A 103 53314 (2021-05-17), http://dx.doi.org/10.1103/PhysRevA.103.053314 doi:10.1103/PhysRevA.103.053314 (ID: 720640) Toggle Abstract
We investigate the properties of a strongly interacting imbalanced mixture of bosonic 41K impurities immersed in a Fermi sea of ultracold 6Li atoms. This enables us to explore the Fermi polaron for large impurity concentrations including the case where they form a Bose-Einstein condensate. The system is characterized by means of radio-frequency injection spectroscopy for tunable interactions using an interspecies Feshbach resonance. We find that the energy of the Fermi polarons formed in the thermal fraction of the impurity cloud remains rather insensitive to the impurity concentration, even as we approach equal densities for both species. The apparent insensitivity to high concentration is consistent with the theoretical prediction, based on Landau's quasiparticle theory, of a weak effective interaction between the polarons. The condensed fraction of the bosonic 41K gas is much denser than its thermal component, which leads to a break-down of the Fermi polaron description. Instead, we observe a new branch in the radio-frequency spectrum with a small energy shift, which is consistent with the presence of Bose polarons formed by 6Li fermions inside the 41K condensate. A closer investigation of the behavior of the condensate by means of Rabi oscillation measurements support this observation, indicating that we have realized Fermi and Bose polarons, two fundamentally different quasiparticles, in one cloud.

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)

2019

Article

B. Huang, I. Fritsche, R. Lous, C. Baroni, J. T. Walraven, E. Kirilov, R. Grimm Breathing Mode of a BEC Repulsively Interacting with a Fermionic Reservoir, Phys. Rev. A 99 41602 (2019-04-03), http://dx.doi.org/10.1103/PhysRevA.99.041602 doi:10.1103/PhysRevA.99.041602 (ID: 720106) Toggle Abstract
We investigate the fundamental breathing mode of a small-sized elongated Bose-Einstein condensate coupled to a large Fermi sea of atoms. Our observations show a dramatic shift of the breathing frequency when the mixture undergoes phase separation at strong interspecies repulsion. We find that the maximum frequency shift in the full phase-separation limit depends essentially on the atom number ratio of the components. We interpret the experimental observations within a model that assumes an adiabatic response of the Fermi sea, or within another model that considers single fermion trajectories for a fully phase-separated mixture. These two complementary models capture the observed features over the full range of interest.

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.
R. Lous, I. Fritsche, M. Jag, F. Lehmann, E. Kirilov, B. Huang, R. Grimm Probing the Interface of a Phase-Separated State in a Repulsive Bose-Fermi Mixture, Phys. Rev. Lett. 120 243403 (2018-02-06), http://dx.doi.org/10.1103/PhysRevLett.120.243403 doi:10.1103/PhysRevLett.120.243403 (ID: 719979) Toggle Abstract
We probe the interface between a phase-separated Bose-Fermi mixture consisting of a small BEC of 41K residing in a large Fermi sea of 6Li. We quantify the residual spatial overlap between the two components by measuring three-body recombination losses for variable strength of the interspecies repulsion. A comparison with a numerical mean-field model highlights the importance of the kinetic energy term for the condensed bosons in maintaining the thin interface far into the phase-separated regime. Our results demonstrate a corresponding smoothing of the phase transition in a system of finite size.
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.

Talk

E. Kirilov Accurate Determination of the Dynamical Polarizability of Dysprosium, 49th annual DAMOP Meeting (Fort Lauderdale, Florida, USA, 2018-05-28) URL (2018-06-01), (ID: 720179)

2015

Article

E. Kirilov, M. J. Mark, M. Segl, H. Nägerl Compact, robust, and spectrally pure diode-laser system with a filtered output and a tunable copy for absolute referencing, Appl. Phys. B Las. Opt. 119/2 0946-2171 (2015-03-07), http://dx.doi.org/10.1007/s00340-015-6049-5 doi:10.1007/s00340-015-6049-5 (ID: 719196) Toggle Abstract
We report on a design of a compact laser system composed of an extended-cavity diode laser with high passive stability and a pre-filter Fabry–Perot cavity. The laser is frequency-stabilized relative to the cavity using a serrodyne technique with a correction bandwidth of ≥6 MHz and a dynamic range of ≥700 MHz. The free-running laser system has a power spectral density (PSD) ≤100 Hz2/Hz centered mainly in the acoustic frequency range. A highly tunable, 0.5–1.3 GHz copy of the spectrally pure output beam is provided, which can be used for further stabilization of the laser system to an ultra-stable reference. We demonstrate a simple one-channel lock to such a reference that brings down the PSD to the sub-Hz level. The tuning, frequency stabilization, and sideband imprinting are achieved by a minimum number of key elements comprising a fibered electro-optic modulator, acousto-optic modulator, and a nonlinear transmission line. The system is easy to operate, scalable, and highly applicable to atomic/molecular experiments demanding high spectral purity, long-term stability, and robustness.

2014

Articles

F. Meinert, M. J. Mark, E. Kirilov, K. Lauber, P. Weinmann, M. Gröbner, A. J. Daley, H. Nägerl Observation of many-body dynamics in long-range tunneling after a quantum quench, Science 344 1262 (2014-06-13), http://dx.doi.org/10.1126/science.1248402 doi:10.1126/science.1248402 (ID: 719039) Toggle Abstract
Quantum tunneling is at the heart of many low-temperature phenomena. In strongly correlated lattice systems, tunneling is responsible for inducing effective interactions, and long-range tunneling substantially alters many-body properties in and out of equilibrium. We observe resonantly enhanced long-range quantum tunneling in one-dimensional Mott-insulating Hubbard chains that are suddenly quenched into a tilted configuration. Higher-order tunneling processes over up to five lattice sites are observed as resonances in the number of doubly occupied sites when the tilt per site is tuned to integer fractions of the Mott gap. This forms a basis for a controlled study of many-body dynamics driven by higher-order tunneling and demonstrates that when some degrees of freedom are frozen out, phenomena that are driven by small-amplitude tunneling terms can still be observed.
F. Meinert, M. J. Mark, E. Kirilov, K. Lauber, P. Weinmann, M. Gröbner, H. Nägerl Interaction-Induced Quantum Phase Revivals and Evidence for the Transition to the Quantum Chaotic Regime in 1D Atomic Bloch Oscillations, Phys. Rev. Lett. 112 193003 (2014-05-15), http://dx.doi.org/10.1103/PhysRevLett.112.193003 doi:10.1103/PhysRevLett.112.193003 (ID: 719073) Toggle Abstract
We study atomic Bloch oscillations in an ensemble of one-dimensional tilted superfluids in the Bose-Hubbard regime. For large values of the tilt, we observe interaction-induced coherent decay and matter-wave quantum phase revivals of the Bloch oscillating ensemble. We analyze the revival period dependence on interactions by means of a Feshbach resonance. When reducing the value of the tilt, we observe the disappearance of the quasiperiodic phase revival signature towards an irreversible decay of Bloch oscillations, indicating the transition from regular to quantum chaotic dynamics.

Poster

M. J. Mark, F. Meinert, E. Kirilov, K. Lauber, P. Weinmann, M. Gröbner, H. Nägerl Many-body dynamics in long-range tunneling after a quantum quench, Workshop on Long Range Interactions in Quantum Systems (Paris, 2014-09-23) (2014-09-23), (ID: 719197)

2013

Article

F. Meinert, M. J. Mark, E. Kirilov, K. Lauber, P. Weinmann, A. J. Daley, H. Nägerl Quantum Quench in an Atomic One-Dimensional Ising Chain, Phys. Rev. Lett. 111 053003 (2013-07-31), http://dx.doi.org/10.1103/PhysRevLett.111.053003 doi:10.1103/PhysRevLett.111.053003 (ID: 718496) Toggle Abstract
We study nonequilibrium dynamics for an ensemble of tilted one-dimensional atomic Bose-Hubbard chains after a sudden quench to the vicinity of the transition point of the Ising paramagnetic to antiferromagnetic quantum phase transition. The quench results in coherent oscillations for the orientation of effective Ising spins, detected via oscillations in the number of doubly occupied lattice sites. We characterize the quench by varying the system parameters. We report significant modification of the tunneling rate induced by interactions and show clear evidence for collective effects in the oscillatory response.