Home > Press > Excitons form superfluid in certain 2D combos: Rice University researchers find ‘paradox’ in ground-state bilayers
Rice University theorists determined that certain combinations of weakly bound 2D materials let holes and electrons combine into excitons at the materials’ ground state. That combination can lead them to condense into a superfluidlike phase. The discovery shows promise for electronic, spintronic and quantum computing applications. (Credit: Yakobson Research Group/Rice University) |
Abstract:
Mixing and matching computational models of 2D materials led scientists at Rice University to the realization that excitons -- quasiparticles that exist when electrons and holes briefly bind -- can be manipulated in new and useful ways.
The researchers identified a small set of 2D compounds with similar atomic lattice dimensions that, when placed together, would allow excitons to form spontaneously. Generally, excitons happen when energy from light or electricity boosts electrons and holes into a higher state.
But in a few of the combinations predicted by Rice materials theorist Boris Yakobson and his team, excitons were observed stabilizing at the materials’ ground state. According to their determination, these excitons at their lowest energy state could condense into a superfluidlike phase. The discovery shows promise for electronic, spintronic and quantum computing applications.
“The very word ‘exciton’ means that electrons and holes ‘jump up’ into a higher energy,” Yakobson said. “All cold systems sit in their lowest-possible energy states, so no excitons are present. But we found a realization of what seems a paradox as conceived by Nevill Mott 60 years ago: a material system where excitons can form and exist in the ground state.”
The open-access study by Yakobson, graduate student Sunny Gupta and research scientist Alex Kutana, all of Rice’s Brown School of Engineering, appears in Nature Communications.
After evaluating many thousands of possibilities, the team precisely modeled 23 bilayer heterostructures, their layers loosely held in alignment by weak van der Waals forces, and calculated how their band gaps aligned when placed next to each other. (Band gaps define the distance an electron has to leap to give a material its semiconducting properties. Perfect conductors -- metals or semimetals like graphene -- have no band gap.)
Ultimately, they produced phase diagrams for each combination, maps that allowed them to view which had the best potential for experimental study.
“The best combinations are distinguished by a lattice parameter match and, most importantly, by the special positions of the electronic bands that form a broken gap, also called type III,” Yakobson said.
Conveniently, the most robust combinations may be adjusted by applying stress through tension, curvature or an external electric field, the researchers wrote. That could allow the phase state of the excitons to be tuned to take on the “perfect fluid” properties of a Bose-Einstein condensate or a superconducting BCS condensate.
“In a quantum condensate, bosonic particles at low temperatures occupy a collective quantum ground state,” Gupta said. “That supports macroscopic quantum phenomena as remarkable as superfluidity and superconductivity.”
“Condensate states are intriguing because they possess bizarre quantum properties and exist on an everyday scale, accessible without a microscope, and only low temperature is required,” Kutana added. “Because they are at the lowest possible energy state and because of their quantum nature, condensates cannot lose energy and behave as a perfect frictionless fluid.
“Researchers have been looking to realize them in various solid and gas systems,” he said. “Such systems are very rare, so having two-dimensional materials among them would greatly expand our window into the quantum world and create opportunities for use in new, amazing devices.”
The best combinations were assemblies of heterostructure bilayers of antimony-tellurium-selenium with bismuth-tellurium-chlorine; hafnium-nitrogen-iodine with zirconium-nitrogen-chlorine; and lithium-aluminum-tellurium with bismuth-tellurium-iodine.
“Except for having similar lattice parameters within each pair, the chemistry compositions appear rather nonintuitive,” Yakobson said. “We saw no way to anticipate the desired behavior without the painstaking quantitative analysis.
“One can never deny a chance to find serendipity -- as Robert Curl said, chemistry is all about getting lucky -- but sifting through hundreds of thousands of material combinations is unrealistic in any lab. Theoretically, however, it can be done.”
Yakobson is the Karl F. Hasselmann Professor of Materials Science and NanoEngineering and a professor of chemistry at Rice.
The U.S. Army Research Office and the Welch Foundation supported the research, with computational facilities provided by the Department of Defense, the Department of Energy and the National Science Foundation.
####
About Rice University
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 3,962 undergraduates and 3,027 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. 4 for quality of life by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger’s Personal Finance.
Follow Rice News and Media Relations via Twitter @RiceUNews.
For more information, please click here
Contacts:
Jeff Falk
713-348-6775
Mike Williams
713-348-6728
Copyright © Rice University
If you have a comment, please Contact us.Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
Related Links |
Rice Department of Materials Science and Nanoengineering:
George R. Brown School of Engineering:
Related News Press |
News and information
Simulating magnetization in a Heisenberg quantum spin chain April 5th, 2024
NRL charters Navy’s quantum inertial navigation path to reduce drift April 5th, 2024
Discovery points path to flash-like memory for storing qubits: Rice find could hasten development of nonvolatile quantum memory April 5th, 2024
2 Dimensional Materials
NRL discovers two-dimensional waveguides February 16th, 2024
'Sudden death' of quantum fluctuations defies current theories of superconductivity: Study challenges the conventional wisdom of superconducting quantum transitions January 12th, 2024
Govt.-Legislation/Regulation/Funding/Policy
NRL charters Navy’s quantum inertial navigation path to reduce drift April 5th, 2024
Discovery points path to flash-like memory for storing qubits: Rice find could hasten development of nonvolatile quantum memory April 5th, 2024
Chemical reactions can scramble quantum information as well as black holes April 5th, 2024
Possible Futures
Discovery points path to flash-like memory for storing qubits: Rice find could hasten development of nonvolatile quantum memory April 5th, 2024
With VECSELs towards the quantum internet Fraunhofer: IAF achieves record output power with VECSEL for quantum frequency converters April 5th, 2024
Spintronics
Quantum materials: Electron spin measured for the first time June 9th, 2023
Linearly assembled Ag-Cu nanoclusters: Spin transfer and distance-dependent spin coupling November 4th, 2022
Chip Technology
Discovery points path to flash-like memory for storing qubits: Rice find could hasten development of nonvolatile quantum memory April 5th, 2024
Utilizing palladium for addressing contact issues of buried oxide thin film transistors April 5th, 2024
HKUST researchers develop new integration technique for efficient coupling of III-V and silicon February 16th, 2024
Quantum Computing
Simulating magnetization in a Heisenberg quantum spin chain April 5th, 2024
Discovery points path to flash-like memory for storing qubits: Rice find could hasten development of nonvolatile quantum memory April 5th, 2024
With VECSELs towards the quantum internet Fraunhofer: IAF achieves record output power with VECSEL for quantum frequency converters April 5th, 2024
Chemical reactions can scramble quantum information as well as black holes April 5th, 2024
Discoveries
Chemical reactions can scramble quantum information as well as black holes April 5th, 2024
New micromaterial releases nanoparticles that selectively destroy cancer cells April 5th, 2024
Utilizing palladium for addressing contact issues of buried oxide thin film transistors April 5th, 2024
Materials/Metamaterials/Magnetoresistance
Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024
Focused ion beam technology: A single tool for a wide range of applications January 12th, 2024
Announcements
NRL charters Navy’s quantum inertial navigation path to reduce drift April 5th, 2024
Discovery points path to flash-like memory for storing qubits: Rice find could hasten development of nonvolatile quantum memory April 5th, 2024
Grants/Sponsored Research/Awards/Scholarships/Gifts/Contests/Honors/Records
Discovery points path to flash-like memory for storing qubits: Rice find could hasten development of nonvolatile quantum memory April 5th, 2024
Chemical reactions can scramble quantum information as well as black holes April 5th, 2024
The latest news from around the world, FREE | ||
Premium Products | ||
Only the news you want to read!
Learn More |
||
Full-service, expert consulting
Learn More |
||