Nav: Home

Controlled electron pulses

November 30, 2016

The discovery of photoemission, the emission of electrons from a material caused by light striking it, was an important element in the history of physics for the development of quantum mechanics. Scientists from the Chair of Laser Physics at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have successfully measured photoemission from sharp metal needles on a scale never before achieved. The researchers' results have been published in the journal Physical Review Letters.

The discovery of photoemission, the emission of electrons from a material caused by light striking it, was an important element in the history of physics for the development of quantum mechanics. Scientists from the Chair of Laser Physics at FAU have successfully measured photoemission from sharp metal needles on a scale never before achieved. The researchers' results have been published in the current issue of the journal Physical Review Letters.

For this two-colour experiment, as they refer to it, the researchers - Dr. Michael Förster, Timo Paschen, Dr. Michael Krüger and Prof. Dr. Peter Hommelhoff - pumped laser pulses with a duration of approximately a nanosecond through a crystal. The crystal combined two photons from the laser pulse. In addition to the strong laser pulse being shone on the crystal, another weak pulse of light with a higher frequency was created. Particularly remarkable was the discovery that the new photons exhibited twice the energy of the original photons. In an interferometer, the FAU scientists separated both colours and determined the direction of vibration, intensity and delay of both pulses.

When the laser pulses meet on the tungsten needle, their energy is concentrated at the vertex of its tip. This limits electron emission to the end of the tip. The researchers observed that, under optimal parameters, they could almost perfectly turn on and off electron emission by controlling the delays between laser pulses. This initially came as a surprise, as light energy (photons) can always be found on the tip; therefore this meant that the relative arrival times of the differently-coloured laser pulses determined whether electrons were or were not emitted.

The researchers came to the idea for this control mechanism by comparing experimental results with calculations by physicists working under Prof. Dr. Joachim Burgdörfer at Technische Universität Wien. They surmised that the electrons could interact with photons from both pulses for emission. This led to two dominant emission paths, but the delay between pulses determined whether these paths would complement or work against each other; emission was either intensified or suppressed in what is known as quantum path interference.

Sharp metal tips have long been used as nearly-punctual electron sources for highest-resolution electron microscopes. Based on the results of this experiment, the researchers hope to create complex electron pulses in the future which could be significant for time-resolved electron microscopy. The experimental results are also of interest for basic research into surface coherence, as the surface of nanostructures can be particularly well controlled and the nanotips produce exceptionally clear measurement signals thanks to their small dimensions.

The renowned journal Physical Review Letters has published the results in its current issue as the Editors' Suggestion. This section highlights particularly interesting scientific results for the readers of the weekly journal, providing insight into fields outside the scope of their own research.
-end-


University of Erlangen-Nuremberg

Related Quantum Mechanics Articles:

Engineers examine chemo-mechanics of heart defect
Elastin and collagen serve as the body's building blocks. Any genetic mutation short-circuiting their function can have a devastating, and often lethal, health impact.
Testing quantum field theory in a quantum simulator
Quantum field theories are often hard to verify in experiments.
Quantum mechanics are complex enough, for now...
Physicists have searched for deviations from standard quantum mechanics, testing whether quantum mechanics requires a more complex set of mathematical rules.
New quantum states for better quantum memories
How can quantum information be stored as long as possible?
Problems in mechanics open the door to the orderly world of chaos
Despite the impression given in most mechanics texts, most non-trivial mechanics problems simply have no analytic solutions.
USC quantum computing researchers reduce quantum information processing errors
USC Viterbi School of Engineering scientists found a new method to reduce the heating errors that have hindered quantum computing.
Quantum satellite device tests technology for global quantum network
Researchers at the National University of Singapore and University of Strathclyde, UK, report first data from a satellite that is testing technology for a global quantum network.
Understanding the mechanics of the urinary bladder
Dr. S. Roccabianca and Dr. T.R. Bush, researchers from Michigan State University compiled an extensive review of the key contributions to understanding the mechanics of the bladder ranging from work conducted in the 1970s through the present time with a focus on material testing and theoretical modeling.
Mechanics of a heartbeat are controlled by molecular strut in heart muscle cells
Using high-resolution microscopy, researchers found that molecular struts called microtubules interact with the heart's contractile machinery to provide mechanical resistance for the beating of the heart, which could provide a better understanding of how microtubules affect the mechanics of the beating heart, and what happens when this goes awry.
Quantum computing closer as RMIT drives towards first quantum data bus
Researchers have trialled a quantum processor capable of routing quantum information from different locations in a critical breakthrough for quantum computing.

Related Quantum Mechanics Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Bias And Perception
How does bias distort our thinking, our listening, our beliefs... and even our search results? How can we fight it? This hour, TED speakers explore ideas about the unconscious biases that shape us. Guests include writer and broadcaster Yassmin Abdel-Magied, climatologist J. Marshall Shepherd, journalist Andreas Ekström, and experimental psychologist Tony Salvador.
Now Playing: Science for the People

#513 Dinosaur Tails
This week: dinosaurs! We're discussing dinosaur tails, bipedalism, paleontology public outreach, dinosaur MOOCs, and other neat dinosaur related things with Dr. Scott Persons from the University of Alberta, who is also the author of the book "Dinosaurs of the Alberta Badlands".