Many striking non-equilibrium phenomena have been discovered or predicted in opticallydriven quantum solids 1 , ranging from light-induced superconductivity 2,3 to Floquetengineered topological phases 4-8 . These effects are expected to lead to dramatic changes in electrical transport, but can only be comprehensively characterized or functionalized with a direct interface to electrical devices that operate at ultrafast speeds 1-8 . Here, we make use of laser-triggered photoconductive switches 9 to measure the ultrafast transport properties of monolayer graphene, driven by a mid-infrared femtosecond pulse of circularly polarized light. The goal of this experiment is to probe the transport signatures of a predicted light-induced topological band structure in graphene 4,5 , similar to the one originally proposed by Haldane 10 . We report the observation of an anomalous Hall effect in the absence of an applied magnetic field. We also extract quantitative properties of the non-equilibrium state. The dependence of the effect on a gate potential used to tune the Fermi level reveals multiple features that reflect the effective band structure expected from Floquet theory. This includes a ∼60 meV wide conductance plateau centered at the Dirac point, where a gap of approximately equal magnitude is expected to open. We also find that when the Fermi level lies within this plateau, the estimated anomalous Hall conductance saturates around ∼1.8±0.4 e 2 /h.Optical driving has been proposed as a means to engineer topological properties in topologically trivial systems 4-8 . One proposal for such a 'Floquet topological insulator' is based on breaking time-reversal symmetry in graphene through a coherent interaction with circularly polarized light 4 . In this theory, the light field drives electrons in circular trajectories through the band structure (Fig. 1a). Close to the Dirac point, these states are predicted to acquire a non-adiabatic Berry phase every optical cycle, which is equal and opposite for the upper and lower band. This time-averaged extra phase accumulation amounts to an energy * These authors contributed equally to this work

We employ a quantum Liouville equation with relaxation to model the recently observed anomalous Hall effect in graphene irradiated by an ultrafast pulse of circularly polarized light. In the weak-field regime, we demonstrate that the Hall effect originates from an asymmetric population of photocarriers in the Dirac bands. By contrast, in the strong-field regime, the system is driven into a non-equilibrium steady state that is well-described by topologically non-trivial Floquet-Bloch bands. Here, the anomalous Hall current originates from the combination of a population imbalance in these dressed bands together with a smaller anomalous velocity contribution arising from their Berry curvature. This robust and general finding enables the simulation of electrical transport from light-induced Floquet-Bloch bands in an experimentally relevant parameter regime and creates a pathway to designing ultrafast quantum devices with Floquet-engineered transport properties.Optical control of functional materials has emerged as an important research front bridging condensed matter physics [1] and ultrafast spectroscopy [2]. Many noteworthy phenomena have been discovered in opticallydriven quantum solids, including light-induced superconductivity [3, 4], various types of photo-initiated insulatormetal transitions [5][6][7][8], light control of microscopic interactions like electron-phonon coupling [9][10][11], and theoretically predicted Floquet-topological phases of matter [12][13][14][15][16]. Floquet-topological phases in particular have stimulated much interest but direct evidence of electronphoton Floquet-dressed states in solids is scarce to this date [17,18], in contrast to the field of artificial lattices [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35].Recently a light-induced anomalous Hall effect was observed in graphene using ultrafast transport techniques [36]. A key challenge for the interpretation of the reported effects lies in the competition between Floquet engineering of Hamiltonians versus the role of electronic population effects. For the case of laser-driven graphene, the latter are particularly important as the pump laser is generically resonant with electronic excitations. Here we provide a theoretical framework within which this class of experiments [36] can be interpreted.A graphene lattice subjected to circular driving has been studied theoretically in a variety of frameworks [12-15, 22, 37-43]. We focus here on the low-frequency driving regime and find that the driven-dissipative dynamics together with the applied bias field plays a crucial role in understanding the transport properties of the Floquetengineered state. Our real-time simulations contain both the population imbalance of excited photocarriers in the Dirac cone of graphene as well as the Floquet-topological Berry curvature of photon-dressed bands. We find that population effects play an important role under the lowfrequency driving used in the experiments in both weak and strong driving limits. In the weak-driving regime,...

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Zusammenfassung Zielsetzung: Analyse von Bedingungsfaktoren f?r die Umsetzung von alkoholbezogenen Interventionen in der haus?rztlichen Praxis. Methode: Fragebogengest?tzte Befragung von 229 Haus?rzten sowie leitfadengest?tzte Fokusgruppeninterviews mit 29 Haus?rzten. Die Fokusgruppenteilnehmer wurden aus der teilnehmenden Grundgesamtheit randomisiert. Ergebnisse: Standardisierte Methoden zur Fr?herkennung von Patienten mit Alkoholproblemen kommen in der haus?rztlichen Praxis kaum zur Anwendung. Die Umsetzung von alkoholbezogenen Ma?nahmen korreliert mit den bisherigen Erfahrungen des Arztes sowie der patientenseitigen Motivation. Als strukturelle Barrieren werden fehlende zeitliche/finanzielle Ressourcen, fehlende Eigenqualifikation und die mangelnde Kooperation mit dem Suchthilfesystem angegeben. Vorhandene Fortbildungsangebote werden anscheinend nur unzureichend wahrgenommen. Schlussfolgerung: Diese Studie zeigt die Komplexit?t der patientenseitigen, arztbezogenen und strukturellen Gr?nde, die eine fl?chendeckende Umsetzung von alkoholbezogenen Interventionen in der haus?rztlichen Praxis verhindern. Modelle zur Verbesserung der Versorgungssituation von Menschen mit Alkoholproblemen in der haus?rztlichen Praxis m?ssen die Bedarfe an Qualifikation, Vernetzung und Finanzierung ber?cksichtigen.