Multiphoton interband excitations of quantum gases in driven optical lattices

Weinberg, Malte; Ölschläger, C.; Sträter, Christoph; Prelle, S.; Eckardt, André; Sengstock, K.; Simonet, Juliette

doi:10.1103/physreva.92.043621

Cited by 84 publications

(73 citation statements)

References 47 publications

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“…Using the above arguments together with the perturbation theory worked out in the appendix of Ref. [46], the threshold driving strength can be evaluated to read 10 (1, ) 2 ,…”

Section: Floquet Perturbation Theorymentioning

confidence: 99%

“…[46]. For this system the driving strength K can be defined as the amplitude of the potential modulation between neighbouring lattice sites in the comoving lattice frame, carrying the dimension of an energy.…”

Section: Floquet Perturbation Theorymentioning

confidence: 99%

“…and the hermitian conjugated terms, where we have employed (45) and (46). The coupling parameter C (b, n) introduced in (14) corresponds to the absolute value of the matrix element coupling the states |0m〉〉 and |2(m - n)〉〉 in Floquet space.…”

Section: Floquet Perturbation Theorymentioning

confidence: 99%

“…Previous work includes theoretical studies of resonant inter-orbital coupling due to both single-particle processes [40][41][42] and two-particle scattering [43][44][45]. Recently, multi-photon interband excitations have also been observed experimentally and explained theoretically by single-particle processes [46].…”

Section: Introductionmentioning

confidence: 99%

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Interband Heating Processes in a Periodically Driven Optical Lattice

Sträter

Eckardt

2016

Zeitschrift Für Naturforschung A

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Abstract:We investigate multi-"photon" interband excitation processes in an optical lattice that is driven periodically in time by a modulation of the lattice depth. Assuming the system to be prepared in the lowest band, we compute the excitation spectrum numerically. Moreover, we estimate the effective coupling parameters for resonant interband excitation processes analytically, employing degenerate perturbation theory in Floquet space. We find that below a threshold driving strength, interband excitations are suppressed exponentially with respect to the inverse driving frequency. For sufficiently low frequencies, this leads to a rather sudden onset of interband heating, once the driving strength reaches the threshold. We argue that this behavior is rather generic and should also be found in lattice systems that are driven by other forms of periodic forcing. Our results are relevant for Floquet engineering, where a lattice system is driven periodically in time in order to endow it with novel properties like the emergence of a strong artificial magnetic field or a topological band structure. In this context, interband excitation processes correspond to detrimental heating.

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“…Using the above arguments together with the perturbation theory worked out in the appendix of Ref. [46], the threshold driving strength can be evaluated to read 10 (1, ) 2 ,…”

Section: Floquet Perturbation Theorymentioning

confidence: 99%

Section: Floquet Perturbation Theorymentioning

confidence: 99%

Section: Floquet Perturbation Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Interband Heating Processes in a Periodically Driven Optical Lattice

Sträter

Eckardt

2016

Zeitschrift Für Naturforschung A

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“…We characterize |Ψ by measuring either the ensemble average of the singlet fraction We begin the experiment by characterizing the change in the Floquet state originating from the undriven ground state for a drive frequency ω/2π = 8 kHz, larger than both the tunneling amplitude t/h = 548 (18) Hz and the strength of the on-site interaction |U |/h. This specific frequency is selected to avoid resonant coupling to higher bands of the optical lattice (the first excited band is h × 26(3) kHz higher in energy) [13]. The on-site interaction U/h is set between −2.4(2) kHz and 2.8(1) kHz.…”

mentioning

confidence: 99%

Controlling the Floquet state population and observing micromotion in a periodically driven two-body quantum system

et al. 2017

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Near-resonant periodic driving of quantum systems promises the implementation of a large variety of novel quantum states, though their preparation and measurement remains challenging. We address these aspects in a model system consisting of interacting fermions in a periodically driven array of double wells created by an optical lattice. The singlet and triplet fractions and the double occupancy of the Floquet states are measured, and their behavior as a function of the interaction strength is analyzed in the high-and low-frequency regimes. We demonstrate full control of the Floquet state population and find suitable ramping protocols and time-scales which adiabatically connect the initial ground state to different targeted Floquet states. The micromotion which exactly describes the time evolution of the system within one driving cycle is observed. Additionally, we provide an analytic description of the model and compare it to numerical simulations.Floquet engineering aims to create novel quantum states through periodic driving, by realising effective Hamiltonians beyond the reach of static systems [1][2][3]. These effective Hamiltonians have been implemented with photons [4,5], solids [6] and ultracold gases in optical lattices [3]. However, preparing and controlling a specific quantum state in a driven system remains in general a challenge. This is particularly the case for many interesting schemes which were realised by driving at low frequencies [4,7] or even close to a characteristic energy scale of the underlying static Hamiltonian. Indeed, driving near-resonantly to the band structure was used to modify kinetic terms in the Hamiltonian [8][9][10][11][12][13][14][15], and modulating close to the interaction energy was proposed to engineer novel interaction terms [16][17][18][19][20]. For all these schemes, the periodic drive strongly couples the static eigenstates, which makes the full control of the population of the different Floquet states and the analysis of their exact time evolution demanding.One important aspect lies in the fundamental differences between Floquet-engineered systems and static Hamiltonians. For example, a periodically driven system is described by a periodic quasi-energy spectrum, and thus has no ground state. Its absence raises an important experimental challenge: How to adiabatically connect the ground state of the initial static Hamiltonian to the targeted Floquet eigenstate? Theory suggests that the population of Floquet states has a non-trivial dependence on the ramp speed and on the exact trajectory which is used in parameter-space [21][22][23][24][25][26], particularly in the case of near-resonant driving which leads to the formation of avoided crossings between quasi-energy levels [27]. In addition to this aspect, we now have to measure observables that are affected by micromotion describing the dynamics of the Floquet system within a driving period. Whilst this micromotion tends to become negligible for infinite driving frequencies, it alters the states significantly for nea...

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