Tracing the nonequilibrium topological state of Chern insulators

Schüler, Michael; Werner, Philipp

doi:10.1103/physrevb.96.155122

Cited by 31 publications

(27 citation statements)

References 61 publications

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“…Practically, we propose that the integrated rates could be experimentally extracted from many individual depletion rate measurements ( 25 , 52 ), corresponding to sampled (fixed) values of ω:

, where the ω l ’s denote the many sampled frequencies separated by Δ ω . This scheme could also be facilitated by the use of multifrequency drives [see the study of Schüler and Werner ( 53 ) for a very recent application of our scheme based on short pulses].…”

Section: Resultsmentioning

confidence: 99%

Probing topology by “heating”: Quantized circular dichroism in ultracold atoms

et al. 2017

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“…Practically, we propose that the integrated rates could be experimentally extracted from many individual depletion rate measurements ( 25 , 52 ), corresponding to sampled (fixed) values of ω:

Section: Resultsmentioning

confidence: 99%

Probing topology by “heating”: Quantized circular dichroism in ultracold atoms

et al. 2017

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“…Another important feature of the noninteracting treatment is the peak occupation directly at K just above ε b ¼ 0. This is a manifestation of a "topological hole" in quantum quenches [74]: Driving a topological phase transition and opening the gap, the orbital character is preserved. This effect is confined to the region close to K, where the time evolution is nonadiabatic no matter how slowly the pump pulse is switched on.…”

Section: Redistribution and Heatingmentioning

confidence: 99%

How Circular Dichroism in Time- and Angle-Resolved Photoemission Can Be Used to Spectroscopically Detect Transient Topological States in Graphene

et al. 2020

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Pumping graphene with circularly polarized light is the archetype of light-tailoring topological bands. Realizing the induced Floquet-Chern-insulator state and demonstrating clear experimental evidence for its topological nature has been a challenge, and it has become clear that scattering effects play a crucial role. We tackle this gap between theory and experiment by employing microscopic quantum kinetic calculations including realistic electron-electron and electron-phonon scattering. Our theory provides a direct link to the build up of the Floquet-Chern-insulator state in light-driven graphene and its detection in time-and angleresolved photoemission spectroscopy (ARPES). This approach allows us to study the robustness of the Floquet features against dephasing and thermalization effects. We also discuss the ultrafast Hall response in the laser-heated state. Furthermore, the induced pseudospin texture and the associated Berry curvature give rise to momentum-dependent orbital magnetization, which is reflected in circular dichroism in ARPES (CD-ARPES). Combining our nonequilibrium calculations with an accurate one-step theory of photoemission allows us to establish a direct link between the build up of the topological state and the dichroic pump-probe photoemission signal. The characteristic features in CD-ARPES are shown to be stable against heating and dephasing effects. Thus, tracing circular dichroism in time-resolved photoemission provides new insights into transient topological properties.

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“…A fully momentumresolved spectroscopy would allow accessing the Berry curvature [4] and quantum metric tensor [7] in ultracold atoms. Besides, time-resolved chiral spectroscopy could be used to reveal the out-of-equilibrium evolution of topological states under a quench [33]. Finally, the quantized circular dichroism revealed in this work could be generalized in view of probing the topological order of strongly-interacting systems, such as the fractional nature of the Hall conductivity in fractional Chern insulators [8].…”

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confidence: 99%

Measuring quantized circular dichroism in ultracold topological matter

et al. 2019

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The topology of two-dimensional materials traditionally manifests itself through the quantization of the Hall conductance, which is revealed in transport measurements [1][2][3]. Recently, it was predicted that topology can also give rise to a quantized spectroscopic response upon subjecting a Chern insulator to a circular drive: Comparing the frequency-integrated depletion rates associated with drives of opposite orientations leads to a quantized response dictated by the topological Chern number of the populated Bloch band [4, 5]. Here we experimentally demonstrate this intriguing topological effect for the first time, using ultracold fermionic atoms in topological Floquet bands. In addition, our depletion-rate measurements also provide a first experimental estimation of the Wannier-spread functional, a fundamental geometric property of Bloch bands [6, 7]. Our results establish topological spectroscopic responses as a versatile probe, which could be applied to access the geometry and topology of many-body quantum systems, such as fractional Chern insulators [8].The discovery of topological states of matter has revolutionized band theory [1-3] by revealing the importance of the Bloch eigenstates and their geometric and topological properties, as captured by the Berry curvature [9] and topological Chern numbers [1-3]. These geometric band properties are associated with the adiabatic motion within a given Bloch band [9], and lead to striking effects such as the anomalous quantum Hall effect [10]. The topological invariant associated with Bloch bands (e.g. the Chern number) cannot be identified through the simple observation of the bulk energy bands, which can be accessed by spectroscopy. However, by evaluating not only the excitation frequencies, but also the excitation strengths [11], geometrical and topological properties become directly accessible via spectroscopy and lead to new topological phenomena [4, 5, 7]. In particular, subjecting a Chern insulator to a circular drive, and comparing the frequencyintegrated depletion rates Γ int ± = ∞ 0 Γ ± (ω)dω resulting from drives of opposite orientation (or chirality, ±), yields a quantized response [4]which is dictated by the Chern number C of the populated band. Here A cell is the area of the unit cell [12], E sp and quantized transport quantized depletion b a Energy Quas imom entum sp sp FIG. 1. Quantized responses in topological matter. a, In the quantum (anomalous) Hall effect, the Hall conductance relating the transverse current density j ⊥ to the applied electric field E follows a quantization law dictated by the Chern number C of the populated Bloch band [1, 9]. b, Our experiment reveals a distinct quantization law [4], which involves the depletion rates Γ ± of a Bloch band (inset) upon circular shaking, where (±) refer to the drive orientation. The differential integrated rate ∆Γ int ± also reveals the Chern number C, but is quadratic with respect to the driving strength E sp , reflecting its dissipative (interband) nature.ω are the strength and frequency of t...

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Tracing the nonequilibrium topological state of Chern insulators

Cited by 31 publications

References 61 publications

Probing topology by “heating”: Quantized circular dichroism in ultracold atoms

Probing topology by “heating”: Quantized circular dichroism in ultracold atoms

How Circular Dichroism in Time- and Angle-Resolved Photoemission Can Be Used to Spectroscopically Detect Transient Topological States in Graphene

Measuring quantized circular dichroism in ultracold topological matter

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