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Li H, Mignolet B, Wachter G, Skruszewicz S, Zherebtsov S, Süssmann F, Kessel A, Trushin SA, Kling NG, Kübel M, Ahn B, Kim D, Ben-Itzhak I, Cocke CL, Fennel T, Tiggesbäumker J, Meiwes-Broer KH, Lemell C, Burgdörfer J, Levine RD, Remacle F, Kling MF. Coherent electronic wave packet motion in C(60) controlled by the waveform and polarization of few-cycle laser fields. PHYSICAL REVIEW LETTERS 2015; 114:123004. [PMID: 25860740 DOI: 10.1103/physrevlett.114.123004] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Indexed: 05/20/2023]
Abstract
Strong laser fields can be used to trigger an ultrafast molecular response that involves electronic excitation and ionization dynamics. Here, we report on the experimental control of the spatial localization of the electronic excitation in the C_{60} fullerene exerted by an intense few-cycle (4 fs) pulse at 720 nm. The control is achieved by tailoring the carrier-envelope phase and the polarization of the laser pulse. We find that the maxima and minima of the photoemission-asymmetry parameter along the laser-polarization axis are synchronized with the localization of the coherent electronic wave packet at around the time of ionization.
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Frolov MV, Manakov NL, Xiong WH, Peng LY, Burgdörfer J, Starace AF. Comment on "Universality of returning electron wave packet in high-order harmonic generation with midinfrared laser pulses". PHYSICAL REVIEW LETTERS 2015; 114:069301. [PMID: 25723250 DOI: 10.1103/physrevlett.114.069301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Indexed: 06/04/2023]
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28
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Wachter G, Lemell C, Burgdörfer J, Sato SA, Tong XM, Yabana K. Ab initio simulation of electrical currents induced by ultrafast laser excitation of dielectric materials. PHYSICAL REVIEW LETTERS 2014; 113:087401. [PMID: 25192124 DOI: 10.1103/physrevlett.113.087401] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2013] [Indexed: 06/03/2023]
Abstract
We theoretically investigate the generation of ultrafast currents in insulators induced by strong few-cycle laser pulses. Ab initio simulations based on time-dependent density functional theory give insight into the atomic-scale properties of the induced current signifying a femtosecond-scale insulator-metal transition. We observe the transition from nonlinear polarization currents during the laser pulse at low intensities to tunnelinglike excitation into the conduction band at higher laser intensities. At high intensities, the current persists after the conclusion of the laser pulse considered to be the precursor of the dielectric breakdown on the femtosecond scale. We show that the transferred charge sensitively depends on the orientation of the polarization axis relative to the crystal axis, suggesting that the induced charge separation reflects the anisotropic electronic structure. We find good agreement with very recent experimental data on the intensity and carrier-envelope phase dependence [A. Schiffrin et al., Nature (London) 493, 70 (2013).
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Furchi M, Pospischil A, Libisch F, Burgdörfer J, Mueller T. Photovoltaic effect in an electrically tunable van der Waals heterojunction. NANO LETTERS 2014; 14:4785-91. [PMID: 25057817 PMCID: PMC4138224 DOI: 10.1021/nl501962c] [Citation(s) in RCA: 413] [Impact Index Per Article: 41.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 07/15/2014] [Indexed: 05/19/2023]
Abstract
Semiconductor heterostructures form the cornerstone of many electronic and optoelectronic devices and are traditionally fabricated using epitaxial growth techniques. More recently, heterostructures have also been obtained by vertical stacking of two-dimensional crystals, such as graphene and related two-dimensional materials. These layered designer materials are held together by van der Waals forces and contain atomically sharp interfaces. Here, we report on a type-II van der Waals heterojunction made of molybdenum disulfide and tungsten diselenide monolayers. The junction is electrically tunable, and under appropriate gate bias an atomically thin diode is realized. Upon optical illumination, charge transfer occurs across the planar interface and the device exhibits a photovoltaic effect. Advances in large-scale production of two-dimensional crystals could thus lead to a new photovoltaic solar technology.
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Horn S, Plasser F, Müller T, Libisch F, Burgdörfer J, Lischka H. A comparison of singlet and triplet states for one- and two-dimensional graphene nanoribbons using multireference theory. Theor Chem Acc 2014. [DOI: 10.1007/s00214-014-1511-8] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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31
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Jenke T, Cronenberg G, Burgdörfer J, Chizhova LA, Geltenbort P, Ivanov AN, Lauer T, Lins T, Rotter S, Saul H, Schmidt U, Abele H. Gravity resonance spectroscopy constrains dark energy and dark matter scenarios. PHYSICAL REVIEW LETTERS 2014; 112:151105. [PMID: 24785025 DOI: 10.1103/physrevlett.112.151105] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Indexed: 06/03/2023]
Abstract
We report on precision resonance spectroscopy measurements of quantum states of ultracold neutrons confined above the surface of a horizontal mirror by the gravity potential of Earth. Resonant transitions between several of the lowest quantum states are observed for the first time. These measurements demonstrate that Newton's inverse square law of gravity is understood at micron distances on an energy scale of 10-14 eV. At this level of precision, we are able to provide constraints on any possible gravitylike interaction. In particular, a dark energy chameleon field is excluded for values of the coupling constant β>5.8×108 at 95% confidence level (C.L.), and an attractive (repulsive) dark matter axionlike spin-mass coupling is excluded for the coupling strength gsgp>3.7×10-16 (5.3×10-16) at a Yukawa length of λ=20 μm (95% C.L.).
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Nagele S, Pazourek R, Wais M, Wachter G, Burgdörfer J. Time-resolved photoemission using attosecond streaking. ACTA ACUST UNITED AC 2014. [DOI: 10.1088/1742-6596/488/1/012004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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33
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Chizhova LA, Rotter S, Jenke T, Cronenberg G, Geltenbort P, Wautischer G, Filter H, Abele H, Burgdörfer J. Vectorial velocity filter for ultracold neutrons based on a surface-disordered mirror system. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:032907. [PMID: 24730913 DOI: 10.1103/physreve.89.032907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Indexed: 06/03/2023]
Abstract
We perform classical three-dimensional Monte Carlo simulations of ultracold neutrons scattering through an absorbing-reflecting mirror system in the Earth's gravitational field. We show that the underlying mixed phase space of regular skipping motion and random motion due to disorder scattering can be exploited to realize a vectorial velocity filter for ultracold neutrons. The absorbing-reflecting mirror system proposed allows beams of ultracold neutrons with low angular divergence to be formed. The range of velocity components can be controlled by adjusting the geometric parameters of the system. First experimental tests of its performance are presented. One potential future application is the investigation of transport and scattering dynamics in confined systems downstream of the filter.
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Pazourek R, Nagele S, Burgdörfer J. Time-resolved photoemission on the attosecond scale: opportunities and challenges. Faraday Discuss 2013; 163:353-76; discussion 393-432. [PMID: 24020211 DOI: 10.1039/c3fd00004d] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The interaction of laser pulses of sub-femtosecond duration with matter opened up the opportunity to explore electronic processes on their natural time scale. One central conceptual question posed by the observation of photoemission in real time is whether the ejection of the photoelectron wavepacket occurs instantaneously, or whether the response time to photoabsorption is finite leading to a time delay in photoemission. Recent experimental progress exploring attosecond streaking and RABBIT techniques find relative time delays between the photoemission from different atomic substates to be of the order of -20 attoseconds. We present ab initio simulations for both one- and two-electron systems which allow the determination of both absolute and relative time delays with -1 attosecond precision. We show that the intrinsic time shift of the photoionization process encoded in the Eisenbud-Wigner-Smith delay time can be unambiguously disentangled from measurement-induced time delays in a pump-probe setting when the photoionized electronic wavepacket is probed by a modestly strong infrared streaking field. We identify distinct contributions due to initial-state polarization, Coulomb-laser coupling in the final continuum state as well as final-state interaction with the entangled residual ionic state. Extensions to multi-electron systems and to the extraction of time information in the presence of decohering processes are discussed.
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Lackner F, Březinová I, Burgdörfer J, Libisch F. Semiclassical wave functions for open quantum billiards. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 88:022916. [PMID: 24032910 DOI: 10.1103/physreve.88.022916] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Indexed: 06/02/2023]
Abstract
We present a semiclassical approximation to the scattering wave function Ψ(r,k) for an open quantum billiard, which is based on the reconstruction of the Feynman path integral. We demonstrate its remarkable numerical accuracy for the open rectangular billiard and show that the convergence of the semiclassical wave function to the full quantum state is controlled by the mean path length or equivalently the dwell time for a given scattering state. In the numerical implementation a cutoff length in the maximum path length or, equivalently, a maximum dwell time τ(max) included implies a finite energy resolution ΔE~τ(max)(-1). Possible applications include leaky billiards and systems with decoherence present.
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Plasser F, Pašalić H, Gerzabek MH, Libisch F, Reiter R, Burgdörfer J, Müller T, Shepard R, Lischka H. Der Multiradikalcharakter ein- und zweidimensionaler Graphen-Nanobänder. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201207671] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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37
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Plasser F, Pašalić H, Gerzabek MH, Libisch F, Reiter R, Burgdörfer J, Müller T, Shepard R, Lischka H. The multiradical character of one- and two-dimensional graphene nanoribbons. Angew Chem Int Ed Engl 2013; 52:2581-4. [PMID: 23355507 PMCID: PMC3648980 DOI: 10.1002/anie.201207671] [Citation(s) in RCA: 167] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2012] [Revised: 11/14/2012] [Indexed: 11/26/2022]
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38
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Krüger M, Schenk M, Förster M, Thomas S, Wachter G, Lemell C, Burgdörfer J, Hommelhoff P. Attosecond physics at a nanoscale metal tip. EPJ WEB OF CONFERENCES 2013. [DOI: 10.1051/epjconf/20134101005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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39
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Lemell C, Dimitriou KI, Arbó DG, Tong XM, Kartashov D, Burgdörfer J, Gräfe S. Low-Energy Peak Structure in Strong-Field Ionization by Mid-Infrared Laser Pulses. EPJ WEB OF CONFERENCES 2013. [DOI: 10.1051/epjconf/20134102016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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40
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Pazourek R, Nagele S, Doblhoff-Dier K, Feist J, Lemell C, Tökési K, Burgdörfer J. Probing scattering phase shifts by attosecond streaking. ACTA ACUST UNITED AC 2012. [DOI: 10.1088/1742-6596/388/1/012029] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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42
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El-Said AS, Wilhelm RA, Heller R, Facsko S, Lemell C, Wachter G, Burgdörfer J, Ritter R, Aumayr F. Phase diagram for nanostructuring CaF(2) surfaces by slow highly charged ions. PHYSICAL REVIEW LETTERS 2012; 109:117602. [PMID: 23005676 DOI: 10.1103/physrevlett.109.117602] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Indexed: 06/01/2023]
Abstract
The impact of individual slow highly charged ions (HCI) on alkaline earth halide and alkali halide surfaces creates nano-scale surface modifications. For different materials and impact energies a wide variety of topographic alterations have been observed, ranging from regularly shaped pits to nanohillocks. We present experimental evidence for the creation of thermodynamically stable defect agglomerations initially hidden after irradiation but becoming visible as pits upon subsequent etching. A well defined threshold separating regions with and without etch-pit formation is found as a function of potential and kinetic energies of the projectile. Combining this novel type of surface defects with the previously identified hillock formation, a phase diagram for HCI induced surface restructuring emerges. The simulation of the energy deposition by the HCI in the crystal provides insight into the early stages of the dynamics of the surface modification and its dependence on the kinetic and potential energies.
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43
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Liertzer M, Feist J, Nagele S, Burgdörfer J. Multielectron transitions induced by neutron impact on helium. PHYSICAL REVIEW LETTERS 2012; 109:013201. [PMID: 23031102 DOI: 10.1103/physrevlett.109.013201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Indexed: 06/01/2023]
Abstract
We explore excitation and ionization by neutron impact as a novel tool for the investigation of electron-electron correlations in helium. We present single- and double-ionization spectra calculated in accurate numerical ab initio simulations for incoming neutrons with kinetic energies of up to 150 keV. The resulting electron spectra are found to be fundamentally different from photoionization or charged particle impact due to the intrinsic many-body character of the interaction. In particular, doubly excited resonances that are strongly suppressed in electron or photon impact become prominent. The ratio of double to single ionization is found to differ significantly from those of photon and charged-particle impact.
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44
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Yoshida S, Reinhold C, Burgdörfer J, Wyker B, Ye S, Dunning F. Analysis of circular wave packets generated by pulsed electric fields. NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH. SECTION B, BEAM INTERACTIONS WITH MATERIALS AND ATOMS 2012; 279-222:4-7. [PMID: 23565015 PMCID: PMC3617732 DOI: 10.1016/j.nimb.2011.10.054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Revised: 09/02/2011] [Indexed: 06/02/2023]
Abstract
We demonstrate that circular wave packets in high Rydberg states generated by a pulsed electric field applied to extreme Stark states are characterized by a position-dependent energy gradient that leads to a correlation between the principal quantum number n and the spatial coordinate. This correlation is rather insensitive to the initial state and can be seen even in an incoherent mix of states such as is generated experimentally allowing information to be placed into, and extracted from, such wave packets. We show that detailed information on the spatial distribution of a circular wave packet can be extracted by analyzing the complex phase of its expansion coefficients.
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45
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Xie X, Roither S, Kartashov D, Persson E, Arbó DG, Zhang L, Gräfe S, Schöffler MS, Burgdörfer J, Baltuška A, Kitzler M. Attosecond probe of valence-electron wave packets by subcycle sculpted laser fields. PHYSICAL REVIEW LETTERS 2012; 108:193004. [PMID: 23003033 DOI: 10.1103/physrevlett.108.193004] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Indexed: 05/12/2023]
Abstract
We experimentally and theoretically demonstrate a self-referenced wave-function retrieval of a valence-electron wave packet during its creation by strong-field ionization with a sculpted laser field. Key is the control over interferences arising at different time scales. Our work shows that the measurement of subcycle electron wave-packet interference patterns can serve as a tool to retrieve the structure and dynamics of the valence-electron cloud in atoms on a sub-10-as time scale.
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46
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Pazourek R, Feist J, Nagele S, Burgdörfer J. Attosecond streaking of correlated two-electron transitions in helium. PHYSICAL REVIEW LETTERS 2012; 108:163001. [PMID: 22680715 DOI: 10.1103/physrevlett.108.163001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Indexed: 06/01/2023]
Abstract
We present fully ab initio simulations of attosecond streaking for ionization of helium accompanied by shakeup of the second electron. This process represents a prototypical case for strongly correlated electron dynamics on the attosecond time scale. We show that streaking spectroscopy can provide detailed information on the Eisenbud-Wigner-Smith time delay as well as on the infrared-field dressing of both bound and continuum states. We find a novel contribution to the streaking delay that stems from the interplay of electron-electron and infrared-field interactions in the exit channel. We quantify all the contributions with attosecond precision and provide a benchmark for future experiments.
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47
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Subramaniam D, Libisch F, Li Y, Pauly C, Geringer V, Reiter R, Mashoff T, Liebmann M, Burgdörfer J, Busse C, Michely T, Mazzarello R, Pratzer M, Morgenstern M. Wave-function mapping of graphene quantum dots with soft confinement. PHYSICAL REVIEW LETTERS 2012; 108:046801. [PMID: 22400872 DOI: 10.1103/physrevlett.108.046801] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2011] [Indexed: 05/31/2023]
Abstract
Using low-temperature scanning tunneling spectroscopy, we map the local density of states of graphene quantum dots supported on Ir(111). Because of a band gap in the projected Ir band structure around the graphene K point, the electronic properties of the QDs are dominantly graphenelike. Indeed, we compare the results favorably with tight binding calculations on the honeycomb lattice based on parameters derived from density functional theory. We find that the interaction with the substrate near the edge of the island gradually opens a gap in the Dirac cone, which implies soft-wall confinement. Interestingly, this confinement results in highly symmetric wave functions. Further influences of the substrate are given by the known moiré potential and a 10% penetration of an Ir surface resonance into the graphene layer.
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48
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Wyker B, Ye S, Dunning FB, Yoshida S, Reinhold CO, Burgdörfer J. Creating and transporting Trojan wave packets. PHYSICAL REVIEW LETTERS 2012; 108:043001. [PMID: 22400833 DOI: 10.1103/physrevlett.108.043001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Indexed: 05/31/2023]
Abstract
Nondispersive localized Trojan wave packets with n(i) ~ 305 moving in near-circular Bohr-like orbits are created and transported to localized near-circular Trojan states of higher n, n(f) ~ 600, by driving with a linearly polarized sinusoidal electric field whose period is slowly increased. The protocol is remarkably efficient with over 80% of the initial atoms being transferred to the higher n states, a result confirmed by classical trajectory Monte Carlo simulations.
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49
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Feist J, Nagele S, Ticknor C, Schneider BI, Collins LA, Burgdörfer J. Attosecond two-photon interferometry for doubly excited states of helium. PHYSICAL REVIEW LETTERS 2011; 107:093005. [PMID: 21929238 DOI: 10.1103/physrevlett.107.093005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2011] [Indexed: 05/31/2023]
Abstract
We show that the correlation dynamics in coherently excited doubly excited resonances of helium can be followed in real time by two-photon interferometry. This approach promises to map the evolution of the two-electron wave packet onto experimentally easily accessible noncoincident single-electron spectra. We analyze the interferometric signal in terms of a semianalytical model which is validated by a numerical solution of the time-dependent two-electron Schrödinger equation in its full dimensionality.
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50
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Bärnthaler A, Rotter S, Libisch F, Burgdörfer J, Gehler S, Kuhl U, Stöckmann HJ. Probing decoherence through Fano resonances. PHYSICAL REVIEW LETTERS 2010; 105:056801. [PMID: 20867943 DOI: 10.1103/physrevlett.105.056801] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2010] [Indexed: 05/26/2023]
Abstract
We investigate the effect of decoherence on Fano resonances in wave transmission through resonant scattering structures. We show that the Fano asymmetry parameter q follows, as a function of the strength of decoherence, trajectories in the complex plane that reveal detailed information on the underlying decoherence process. Dissipation and unitary dephasing give rise to manifestly different trajectories. Our predictions are successfully tested against microwave experiments using metal cavities with different absorption coefficients and against previously published data on transport through quantum dots. These results open up new possibilities for studying the effect of decoherence in a wide array of physical systems where Fano resonances are present.
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