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J Burgdörfer

Publications and source records attributed to J Burgdörfer.

At least 19 recordsLinked to original sources
PubMed2006

Nanowires with surface disorder: giant localization lengths and quantum-to-classical crossover.

We investigate electronic quantum transport through nanowires with one-sided surface roughness. A magnetic field perpendicular to the scattering region is shown to lead to exponentially diverging localization lengths in the quantum-to-classical crossover regime. This effect can be quantitatively accounted for by tunneling between the regular and the chaotic components of the underlying mixed classical phase space.

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PubMed2006

Interference oscillations in the angular distribution of laser-ionized electrons near ionization threshold.

We analyze the two-dimensional momentum distribution of electrons ionized by few-cycle laser pulses in the transition regime from multiphoton absorption to tunneling by solving the time-dependent Schrödinger equation and by a classical-trajectory Monte-Carlo simulation with tunneling (CTMC-T). We find a complex two-dimensional interference pattern that resembles above threshold ionization (ATI) rings at higher energies and displays Ramsauer-Townsend-type diffraction oscillations in the angular distribution near threshold. CTMC-T calculations provide a semiclassical explanation for the dominance of selected partial waves. While the present calculation pertains to hydrogen, we find surprising qualitative agreement with recent experimental data for rare gases [A. Rudenko, J. Phys. B 37, L407 (2004)].

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PubMed2005

Engineering very-high-n polarized Rydberg states using tailored half-cycle-pulse sequences.

We show that strongly polarized very-high-n (n approximately 600) potassium Rydberg atoms can be produced by manipulating lower-n (n approximately 350) polarized atoms using a tailored sequence of ultrashort half-cycle pulses (HCPs). The protocol for this involves first a weak HCP that generates transient phase-space localization whereupon a second large HCP of opposite polarity excites the electron to a broad distribution of highly elongated states. This distribution is then refocused by a short periodic train of HCPs using the properties of (un)stable manifolds near fixed points in phase space.

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PubMed2004

Tunable Fano resonances in transport through microwave billiards.

We present a tunable microwave scattering device that allows the controlled variation of Fano line shape parameters in transmission through quantum billiards. Transport in this device is nearly fully coherent. By comparison with quantum calculations, employing the modular recursive Green's-function method, the scattering wave function and the degree of residual decoherence can be determined. The parametric variation of Fano line shapes in terms of interacting resonances is analyzed.

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PubMed2004

Observation of light-phase-sensitive photoemission from a metal.

We demonstrate that multiphoton-induced photoelectron emission from a gold surface caused by low-energy (unamplified) 4-fs, 750-nm laser pulses is sensitive to the timing of electric field oscillations with respect to the pulse peak. This observation confirms recent theoretical predictions and opens the door to measuring the absolute value of the carrier-envelope phase difference of few-cycle light pulses with a solid-state detector.

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PubMed2003

Electron emission from metal surfaces by ultrashort pulses: determination of the carrier-envelope phase.

The phase varphi of the field oscillations with respect to the peak of a laser pulse influences the light field evolution as the pulse length becomes comparable to the wave cycle and, hence, affects the interaction of intense few-cycle pulses with matter. We theoretically investigate photoelectron emission induced by an intense, few-cycle laser pulse from a metal surface (jellium) within the framework of time-dependent density functional theory and find a pronounced varphi dependence of the photocurrent. Our results reveal a promising route to measuring varphi of few-cycle light pulses (tau<6 fs at lambda=0.8 microm) at moderate intensity levels (I(p) approximately 10(12) W/cm(2)) using a solid-state device.

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PubMed2001

Kinetically assisted potential sputtering of insulators by highly charged ions.

A new form of potential sputtering has been found for impact of slow ( < or = 1500 eV) multiply charged Xe ions (charge states up to q = 25) on MgO(x). In contrast to alkali-halide or SiO2 surfaces this mechanism requires the simultaneous presence of electronic excitation of the target material and of a kinetically formed collision cascade within the target in order to initiate the sputtering process. This kinetically assisted potential sputtering mechanism has been identified to be present for other insulating surfaces as well.

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