Cooperative Phenomena

Transcription

1 Cooperative Phenomena Frankfurt am Main Kaiserslautern Mainz B1, B2, B4, B6, B13N A7, A9, A12 A10, B5, B8 Materials Design - Synthesis & Modelling A3, A8, B1, B2, B4, B6, B9, B11, B13N A5, A7, A9, A12, B3 A10, B5, B8, B12 A5, A7, A9, A12, B3 A10, B5, B8, B12 Cooperative Phenomena A3, A8, B1, B2, B4, B6, B9, B11, B13N Excitations & Interactions 1

2 Cooperative Phenomena critical phenomena non-equilibrium dynamics quantum magnetism phonon & polaron physics Mott transition superconductivity spin liquids 2

3 Cooperative Phenomena Model-based systems Solid state real materials 3

4 Cooperative Phenomena Model-based systems Solid state real materials 3

5 Cooperative Phenomena Experiment Theory A7 A9 A10 Collective effects and instabilities of a magnon gas Ultracold Bose gases with variable interactions Designing spin-spin interactions in cold ion crystals A3 A5 Inhomogeneous quantum phases and dynamics in ultracold gases and hybrid atom-ion systems Advanced numerical methods for correlated quantum gases A12 Multi-polaron effects with spinless and spinful impurities in a bosonic quantum gas A8 Interacting magnons and critical behaviour of bosons B1 B2 B3 B4 B5 B6 B7 E B8 B9 B10 E B11 B12 B13 N 4

6 Critical phenomena & dynamics Bose-Einstein condensation in an ultra-hot gas of pumped magnons A7 Pumping power 1 W Pumping power 4 W Pumping power 25 W Low temp. magnon gas Hot magnon gas Ultra-hot magnon gas Experimental method Time-, space- and wavevector-resolved BLS spectroscopy evaporative supercooling à formation of magnon BEC after pumping is switched off Nature Commun. 5, 4452 (2014) A7 A8 magnon-phonon scattering à different thermalization rates and two magnon temperature PRB 89, (2014) 5

7 Critical phenomena & dynamics Dynamics of magnon gases in spatially confined structures A7 Microsized parametric amplifier APL 99, (2011) APL 103, (2013) APL 104, (2014) APL 104, (2014) APL 105, (2014) à toolbox for magnon BECs in micro-sized samples Next: Spatially confined magnon condensates and coherent magnon transport Coherent interactions & phase transitions in magnon gases Theory of magnon-phonon interaction and non-equilibrium dynamics A7 A8 6

8 Critical phenomena & dynamics Dimensional phase transition from 1D to 3D A9 B3 lattice height study coupled 1D Bose gases à 3D condensation extract phase diagram & comparison with theory ultracold bosons in an optical lattice decoupled 1D 3D condensate PRL 113, (2014) µ/kb T Next: Transport in mixed dimensions A9 B3 superimpose lattice in longitudinal direction à coupled 1D Mott insulators 7

9 Critical phenomena & dynamics Next: Strongly correlated mass transport A3 A9 non-equilibrium tunneling transport of atoms in a Mott insulator state Quench dynamics of strongly correlated bosons in 2d, 3d dynamical arrest A3 A5 A9 8

10 Critical phenomena & dynamics Dynamical arrest & quantum distillation A3 A5 non-adiabatic evolution during lattice ramp fermions Phys. Rev. Lett. 110, (2013). bosons, 1D Phys. Rev. A 110, (2012). Negative differential conductivity non-equilibirum current-voltage initial condition characteristics A9 appearance of NDC arxiv:

11 Quantum Magnetism Tunable magnetic order A3 SS bosonic magnetism on triangular lattice frustration SDW Phys. Rev. A 86, (2012) tb/u XY ferromag stripe SDW SS t a /U 10

12 Phonon and Polaron physics Hybrid quantum simulator A3 A10 ultracold atoms in a dynamical lattice of trapped ions Phys. Rev. Lett. 111, (2013) emulating electronic solids including phonons atoms ions Paul trap layer Next: A10 planar Paul trap with Yb+ crystal magnetic trap for Rb BEC tight confinement à 1D atom-ion system Magnetic trapping layer A3 A5 A9 11

13 Polarons Phonon in and Solid Polaron State physics Systems Polaron in solid-state physics Next: Bose-polaron of neutral impurities in a BEC A12 simulate Fröhlich polaron with tunable impurity-bec interactions spectroscopy on weak and strongly coupled polarons lattice-polaron or quasi free-polaron dynamics BEC density A3 A5 A10 weak intermediate strong coupling 12

14 studies of polarons in a BEC exist (see for example [26 29]), no experimental observation has yet been achieved, although neutral impurities in ultracold bosonic baths have been realized [30 33]. We will focus on e ects of multiple bands, tilted lattices and interactions between impurities. We treat the BEC within the Bogoliubov approximation, and extend the non-perturbative LangFirsov transformation [27] to a system with two (impurity) bands, which yields an e ective Polaron Hamiltonian including coherent hopping and longer-range interactions Phonon and Polaron physics Hp i,j Next: J a i a j i, a i a i s! s bs bs i,j, Vi,j ni nj where a and b denote Cs atoms and Bogoliubov phonons, i, j are lattice site indices and labels the Bloch bands. This system can then be described by the Lindblad master equation d p Theory of polarons & impurity dynamics lattices and BECs i Hp, in p p dt (5) A3 (6) A5 where the dissipator models the residual Markovian coupling to the phononic bath, capturing dissipative impurity dynamics beyond Fermi s Golden Bloch oscillations, multiband physics Rule. One focus will be on polaronic Bloch oscillations in an accelerated lattice, which can be monitored detection ofand polaron by RFdepends spectroscopy in situ whose frequency on the strongly enhanced e ective mass of the polaron. While singleband polaronic Bloch oscillations have been studied Figure 5: Cs impurity in a Rb BEC. Due to many-polaron phases before [27, 29], little is known about the e ect of a an optical lattice, multiple Bloch bands of the second impurity Bloch into which single atoms impurity arise. relaxation dynamics ofband, supersonic can be excited in a controlled fashion. We will investigate damped Bloch oscillations and Landauimpurity in tunneling, BEC and calculate the drift velocity of the polarons and the resulting current-voltage Zener characteristics. After controlled preparation of an impurity in the excited band, we will calculate the interband relaxation rate and the decoherence time that have already been measured in a di erent setup with 6 Li in 23 Na [34], and the resulting non-equilibrium steady state which results when the interband drive (induced e.g. by microwaves) is continuous. In addition, the RF response of the dilute impurity system will be calculated, as previously for the single-band case [35], and measured in project A12 (Widera), thus allowing for detection of the polaron binding energy and the quasiparticle residue. By combining an accelerated optical lattice with periodic lattice modulation, photon-assisted tunneling resonances will be studied [36], where we expect the polaron mass to be visible. Transregio 49furthermore investigate the case of multiple bosonic impurities, where clustering of polarons We will Frankfurt Kaiserslautern / Mainz [37]/ or long-range ordered polaronic phases are expected. These calculations will be based on bosonic Gutzwiller and R-DMFT, applied to the e ective polaron Hamiltonian (5). The residual dissipative coupling to the phonon bath in the steady state will first be neglected, and later included via 13

15 Cooperative Phenomena critical phenomena non-equilibrium dynamics quantum magnetism phonon & polaron physics Mott transition Superconductivity spin liquids 14

16 Cooperative Phenomena critical phenomena non-equilibrium dynamics quantum magnetism phonon & polaron physics Mott transition superconductivity spin liquids 14

17 Cooperative Phenomena Model-based systems Solid-state real materials 15