Picosecond Resolution in Scanning Tunneling Microscopy

Nunes, G.; Freeman, M. R.

doi:10.1126/science.262.5136.1029

Cited by 156 publications

(79 citation statements)

References 16 publications

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“…The third class of combined microscopes [18][19][20][21][22] couples an STM tunnel junction with laser light. The tunnel junction is illuminated with two fine-tuned optical frequencies.…”

Section: Introductionmentioning

confidence: 99%

Effect of tip geometry on contrast and spatial resolution of the near-field microwave microscope

Imtiaz

Anlage

2006

Journal of Applied Physics

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The Near-Field Scanning Microwave Microscope (NSMM) can quantitatively image materials properties at length scales far shorter than the free space wavelength (λ). Here we report a study of the effect of tip-geometry on the NSMM signals. This particular NSMM utilizes scanning tunneling microscopy (STM) for distance-following control. We systematically examined many commercially available STM tips, and find them to have a conical structure on the macroscopic scale, with an embedded sphere (of radius r sphere ) at the apex of the tip. The r sphere values used in the study ranged from 0.1 μm to 12.6 μm. Tips with larger r sphere show good signal contrast (as measured by the frequency shift (Δf) signal between tunneling height and 2 μm away from the sample) with NSMM. For example, the tips with r sphere = 8 μm give signal contrast of 1000 kHz compared to 85 kHz with a tip of r sphere = 0.55 μm. However, large r sphere tips distort the topographic features acquired through STM. A theoretical model is used to understand the tip-to-sample interaction. The model a email address: anlage@umd.edu 1 quantitatively explains the measured change in quality factor (Q) as a function of height over bulk Copper and Silicon samples.

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“…The third class of combined microscopes [18][19][20][21][22] couples an STM tunnel junction with laser light. The tunnel junction is illuminated with two fine-tuned optical frequencies.…”

Section: Introductionmentioning

confidence: 99%

Effect of tip geometry on contrast and spatial resolution of the near-field microwave microscope

Imtiaz

Anlage

2006

Journal of Applied Physics

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“…This addresses, e.g., spin-resolved scanning-tunneling microscope experiments [30][31][32][33][34]. We choose B ini = ∞ to initially fully polarize the impurity spin.…”

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Inertia effects in the real-time dynamics of a quantum spin coupled to a Fermi sea

Sayad

Rausch

Potthoff

2016

EPL

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-Spin dynamics in the Kondo impurity model, initiated by suddenly switching the direction of a local magnetic field, is studied by means of the time-dependent density-matrix renormalization group. Quantum effects are identified by systematic computations for different spin quantum numbers S and by comparing with tight-binding spin-dynamics theory for the classical-spin Kondo model. We demonstrate that, besides the conventional precessional motion and relaxation, the quantum-spin dynamics shows nutation, similar to a spinning top. Opposed to semiclassical theory, however, the nutation is efficiently damped on an extremely short time scale. The effect is explained in the large-S limit as quantum dephasing of the eigenmodes in an emergent two-spin model that is weakly entangled with the bulk of the system. We argue that, apart from the Kondo effect, the damping of nutational motion is essentially the only characteristics of the quantum nature of the spin. Qualitative agreement between quantum and semiclassical spin dynamics is found down to S = 1/2.Introduction.-The paradigmatic system to study the real-time dynamics of a spin-1/2 coupled to a Fermi sea is the Kondo model [1]. It is mainly considered as a generic model for the famous Kondo effect [2], namely screening of the impurity spin by a mesoscopically large number of electrons in a thermal state with temperature below the Kondo temperature T K ∼ exp(−1/Jρ), where J is the strength of the exchange coupling and ρ is the density of states. The Kondo effect is a true quantum effect which originates from the two-fold spin degeneracy and is protected by time-reversal symmetry. Longitudinal spin dynamics, such as the time-dependent Kondo screening, has been studied recently [3,4] by starting from an initial state with a fully polarized spin, which can be prepared with the help of local magnetic field. The longitudinal dynamics is initiated by suddenly switching off the field.

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“…Hamers et al determined the recombination lifetime of photoexcited carriers in Si, in their pioneering work, by analyzing the observed surface photovoltage (SPV) by simulation [10], and a method that involves the combined use of an optical pulse pair and STM was proposed as photoconductive-gate STM (PG-STM) [11][12][13][14][15][16][17][18]. However, the spatial and temporal resolutions of the former method were limited to the 1 µm scale and laser-pulse repetition rate, respectively, and the PG-STM probes dI/dV or the quantity mediating the signal rather than the transient effect itself [18].…”

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confidence: 99%

Real-space imaging of transient carrier dynamics by nanoscale pump–probe microscopy

et al. 2010

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Picosecond Resolution in Scanning Tunneling Microscopy

Cited by 156 publications

References 16 publications

Effect of tip geometry on contrast and spatial resolution of the near-field microwave microscope

Effect of tip geometry on contrast and spatial resolution of the near-field microwave microscope

Inertia effects in the real-time dynamics of a quantum spin coupled to a Fermi sea

Real-space imaging of transient carrier dynamics by nanoscale pump–probe microscopy

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