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.

University of Erlangen-Nuremberg

Related Quantum Mechanics Articles:

Quantum leap: Photon discovery is a major step toward at-scale quantum technologies
A team of physicists at the University of Bristol has developed the first integrated photon source with the potential to deliver large-scale quantum photonics.
Understanding mechanics and materials though evolution and biomaterials
Studying the evolution of bodily processes millions of years ago as well as the properties of today's biomaterials could improve soft robotics design and inform materials science research.
USTC realizes the first quantum-entangling-measurements-enhanced quantum orienteering
Researchers enhanced the performance of quantum orienteering with entangling measurements via photonic quantum walks.
A convex-optimization-based quantum process tomography method for reconstructing quantum channels
Researchers from SJTU have developed a convex-optimization-based quantum process tomography method for reconstructing quantum channels, and have shown the validity to seawater channels and general channels, enabling a more precise and robust estimation of the elements of the process matrix with less demands on preliminary resources.
What a pair! Coupled quantum dots may offer a new way to store quantum information
Researchers at the National Institute of Standards and Technology (NIST) and their colleagues have for the first time created and imaged a novel pair of quantum dots -- tiny islands of confined electric charge that act like interacting artificial atoms.
In leap for quantum computing, silicon quantum bits establish a long-distance relationship
In an important step forward in the quest to build a quantum computer using silicon-based hardware, researchers at Princeton have succeeded in making possible the exchange of information between two qubits located relatively far apart -- about the length of a grain of rice, which is a considerable distance on a computer chip.
Artificial intelligence algorithm can learn the laws of quantum mechanics
Artificial intelligence can be used to predict molecular wave functions and the electronic properties of molecules.
A new quantum data classification protocol brings us nearer to a future 'quantum internet'
A new protocol created by researchers at the Universitat Autònoma de Barcelona sorts and classifies quantum data by the state in which they were prepared, with more efficiency than the equivalent classical algorithm.
Bridge between quantum mechanics and general relativity still possible
An international team of researchers developed a unified framework that would account for this apparent break down between classical and quantum physics, and they put it to the test using a quantum satellite called Micius.
'Poor man's qubit' can solve quantum problems without going quantum
Researchers have built and demonstrated the first hardware for a probabilistic computer, a possible way to bridge the gap between classical and quantum computing.
More Quantum Mechanics News and Quantum Mechanics Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Making Amends
What makes a true apology? What does it mean to make amends for past mistakes? This hour, TED speakers explore how repairing the wrongs of the past is the first step toward healing for the future. Guests include historian and preservationist Brent Leggs, law professor Martha Minow, librarian Dawn Wacek, and playwright V (formerly Eve Ensler).
Now Playing: Science for the People

#566 Is Your Gut Leaking?
This week we're busting the human gut wide open with Dr. Alessio Fasano from the Center for Celiac Research and Treatment at Massachusetts General Hospital. Join host Anika Hazra for our discussion separating fact from fiction on the controversial topic of leaky gut syndrome. We cover everything from what causes a leaky gut to interpreting the results of a gut microbiome test! Related links: Center for Celiac Research and Treatment website and their YouTube channel
Now Playing: Radiolab

The Flag and the Fury
How do you actually make change in the world? For 126 years, Mississippi has had the Confederate battle flag on their state flag, and they were the last state in the nation where that emblem remained "officially" flying.  A few days ago, that flag came down. A few days before that, it coming down would have seemed impossible. We dive into the story behind this de-flagging: a journey involving a clash of histories, designs, families, and even cheerleading. This show is a collaboration with OSM Audio. Kiese Laymon's memoir Heavy is here. And the Hospitality Flag webpage is here.