Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Ultracold atoms used to verify 1963 prediction about 1D electrons

05.09.2018

Rice University, University of Geneva study focuses on theory that's increasingly relevant to chipmakers

Rice University atomic physicists have verified a key prediction from a 55-year-old theory about one-dimensional electronics that is increasingly relevant thanks to Silicon Valley's inexorable quest for miniaturization.


Using ultracold lithium atoms confined by intersecting laser beams, physicists from Rice University and the University of Geneva confirmed a 1963 prediction that the charge wave from an excited electron moves faster in a one-dimensional electron gas as interaction strength between the electrons increases.

Credit: Jeff Fitlow/Rice University

Usage Restrictions: For news reporting purposes only.

"Chipmakers have been shrinking feature sizes on microchips for decades, and device physicists are now exploring the use of nanowires and nanotubes where the channels that electrons pass through are almost one-dimensional," said Rice experimental physicist Randy Hulet.

"That's important because 1D is a different ballgame in terms of electron conductance. You need a new model, a new way of representing reality, to make sense of it."

With IBM and others committed to incorporating one-dimensional carbon nanotubes into integrated circuits, chip designs will increasingly need to account for 1D effects that arise from electrons being fermions, antisocial particles that are unwilling to share space.

The 1D implications of this standoffishness caught the attention of physicists Sin-Itiro Tomonaga and J.M. Luttinger, whose model of 1D electron behavior was published in 1963. A key prediction of Tomonaga-Luttinger liquid (TLL) theory is that exciting one electron in a 1D wire leads to a collective, organized response from every electron in the wire.

Stranger still, because of this collective behavior, TLL theory predicts that a moving electron in 1D will seemingly split in two and travel at different speeds, despite the fact that electrons are fundamental particles that have no constituent parts. This strange breakup, known as spin-charge separation, instead involves two inherent properties of the electron -- negative charge and angular momentum, or "spin."

In a study online this week in Physical Review Letters, Hulet, University of Geneva theoretical physicist Thierry Giamarchi and their colleagues used another type of fermion -- ultracold lithium atoms cooled to within 100 billionths of a degree of absolute zero -- to both verify the predicted speed that charge waves move in 1D and offer confirmation that 1D charge waves increase their speed in proportion to the strength of the interaction between them.

"In a one-dimensional wire, electrons can move to the left or to the right, but they cannot go around other electrons," said Hulet, Rice's Fayez Sarofim Professor of Physics. "If you add energy to the system, they move, but because they're fermions and can't share space, that movement, or excitation, causes a kind of chain reaction.

"One electron moves, and it nudges the next one to move and the one next to that one and so on, causing the energy you've added to move down the wire like a wave," Hulet said. "That single excitation has created a ripple everywhere in the wire."

In their experiments, Hulet's team used lithium atoms as stand-ins for electrons. The atoms are trapped and slowed with lasers that oppose their motion. The slower they go, the colder the lithium atoms become, and at temperatures far colder than any in nature, the atoms behave like electrons. More lasers are used to form optical waveguides, one-dimensional tubes wide enough for just one atom. Despite the effort needed to create these conditions, Hulet said the experiments offer a big advantage.

"We can use a magnetic field in our experiment to tune the strength of the repulsive interaction between the lithium atoms," Hulet said. "In studying these collective, or correlated electron behaviors, interaction strength is an important factor. Stronger or weaker electron interactions can produce wholly different effects, but it's extraordinarily difficult to study this with electrons because of the inability to directly control interactions. With ultracold atoms, we can essentially dial the interaction strength to any level we want and watch what happens."

While previous groups have measured the speed of collective waves in nanowires and in gases of ultracold atoms, none had measured it as a function of interaction strength, Hulet said.

"Charge excitations are predicted to move faster with increasing interaction strength, and we showed that," he said. "Thierry Giamarchi, who literally wrote the book on this topic, used TLL theory to predict how the charge wave would behave in our ultracold atoms, and his predictions were borne out in our experiments."

Having that ability to control interactions also sets the stage for testing the next TLL prediction: The speed of charge waves and spin waves diverge with increasing interaction strength, meaning that as electrons are made to repel one another with greater force, charge waves will travel faster and spin waves will travel slower.

Now that the team has verified the predicted behavior of charge waves, Hulet said they next plan to measure spin waves to see if they behave as predicted.

"The 1D system is a paradigm for strongly correlated electron physics, which plays a key role in many things we'd like to better understand, like high-temperature superconductivity, heavy fermion materials and more," Hulet said.

###

Hulet also is a member of the Rice Center for Quantum Materials. Giamarchi is a professor of condensed matter physics at the University of Geneva and a permanent member of the French National Center for Scientific Research.

Additional study co-authors include Rice graduate student Ya-Ting Chang; former Rice graduate students Tsung-Lin Yang, the study's lead author, and Zhenghao Zhao; former Rice visiting student researcher Chung-You Shih; and former University of Geneva research scientist Pjotrs Grisins. The research was supported by the Army Research Office's Multidisciplinary University Research Initiative, the Office of Naval Research, the National Science Foundation and the Swiss National Science Foundation.

The DOI of the Physical Review Letters paper is: 10.1103/PhysRevLett.121.103001

A copy of the paper is available at: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.103001

Related research from Rice:

Ultracold atom waves may shed light on rogue ocean killers -- April 28, 2017 http://news.rice.edu/2017/04/28/ultracold-atom-waves-may-shed-light-on-rogue-ocean-killers/

Simulating superconducting materials with ultracold atoms -- Feb. 23, 2015 http://news.rice.edu/2015/02/23/simulating-superconducting-materials-with-ultracold-atoms/

Ultracold disappearing act -- Nov. 2, 2014 http://news.rice.edu/2014/11/02/ultracold-disappearing-act/

One-dimensional window on superconductivity, magnetism -- Sept. 29, 2010 http://news.rice.edu/2010/09/29/one-dimensional-window-on-superconductivity-magnetism-2/

Rice physicists find reappearing quantum trios -- Dec. 11, 2009 http://news.rice.edu/2009/12/11/rice-physicists-find-reappearing-quantum-trios-2/

Rice awarded $5M for light-based crystal simulator -- Sept. 23, 2009 http://news.rice.edu/2009/09/23/rice-awarded-5m-for-light-based-crystal-simulator/

Ultracold test produces long-sought quantum mix -- Dec. 22, 2005 http://news.rice.edu/2005/12/22/ultracold-test-produces-long-sought-quantum-mix/

Rice physicists observe new 'atom wave' phenomena -- May 1, 2002 https://www.eurekalert.org/pub_releases/2002-05/ru-rpo043002.php

This release can be found online at news.rice.edu.

Follow Rice News and Media Relations via Twitter @RiceUNews.

Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,970 undergraduates and 2,934 graduate students, Rice's undergraduate student-to-faculty ratio is just under 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for lots of race/class interaction and No. 2 for quality of life by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to http://tinyurl.com/RiceUniversityoverview.

Media Contact

David Ruth
david@rice.edu
713-348-6327

 @RiceUNews

http://news.rice.edu 

David Ruth | EurekAlert!
Further information:
http://dx.doi.org/10.1103/PhysRevLett.121.103001

More articles from Physics and Astronomy:

nachricht Double layer of graphene helps to control spin currents
18.10.2019 | University of Groningen

nachricht Analysis of Galileo's Jupiter entry probe reveals gaps in heat shield modeling
17.10.2019 | American Institute of Physics

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Solving the mystery of quantum light in thin layers

A very special kind of light is emitted by tungsten diselenide layers. The reason for this has been unclear. Now an explanation has been found at TU Wien (Vienna)

It is an exotic phenomenon that nobody was able to explain for years: when energy is supplied to a thin layer of the material tungsten diselenide, it begins to...

Im Focus: An ultrafast glimpse of the photochemistry of the atmosphere

Researchers at Ludwig-Maximilians-Universitaet (LMU) in Munich have explored the initial consequences of the interaction of light with molecules on the surface of nanoscopic aerosols.

The nanocosmos is constantly in motion. All natural processes are ultimately determined by the interplay between radiation and matter. Light strikes particles...

Im Focus: Shaping nanoparticles for improved quantum information technology

Particles that are mere nanometers in size are at the forefront of scientific research today. They come in many different shapes: rods, spheres, cubes, vesicles, S-shaped worms and even donut-like rings. What makes them worthy of scientific study is that, being so tiny, they exhibit quantum mechanical properties not possible with larger objects.

Researchers at the Center for Nanoscale Materials (CNM), a U.S. Department of Energy (DOE) Office of Science User Facility located at DOE's Argonne National...

Im Focus: Novel Material for Shipbuilding

A new research project at the TH Mittelhessen focusses on the development of a novel light weight design concept for leisure boats and yachts. Professor Stephan Marzi from the THM Institute of Mechanics and Materials collaborates with Krake Catamarane, which is a shipyard located in Apolda, Thuringia.

The project is set up in an international cooperation with Professor Anders Biel from Karlstad University in Sweden and the Swedish company Lamera from...

Im Focus: Controlling superconducting regions within an exotic metal

Superconductivity has fascinated scientists for many years since it offers the potential to revolutionize current technologies. Materials only become superconductors - meaning that electrons can travel in them with no resistance - at very low temperatures. These days, this unique zero resistance superconductivity is commonly found in a number of technologies, such as magnetic resonance imaging (MRI).

Future technologies, however, will harness the total synchrony of electronic behavior in superconductors - a property called the phase. There is currently a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

International Symposium on Functional Materials for Electrolysis, Fuel Cells and Metal-Air Batteries

02.10.2019 | Event News

NEXUS 2020: Relationships Between Architecture and Mathematics

02.10.2019 | Event News

Optical Technologies: International Symposium „Future Optics“ in Hannover

19.09.2019 | Event News

 
Latest News

Energy Flow in the Nano Range

18.10.2019 | Power and Electrical Engineering

MR-compatible Ultrasound System for the Therapeutic Application of Ultrasound

18.10.2019 | Medical Engineering

Double layer of graphene helps to control spin currents

18.10.2019 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>