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Slot MR, Maximenko Y, Haney PM, Kim S, Walkup DT, Strelcov E, Le ST, Shih EM, Yildiz D, Blankenship SR, Watanabe K, Taniguchi T, Barlas Y, Zhitenev NB, Ghahari F, Stroscio JA. A quantum ruler for orbital magnetism in moiré quantum matter. Science 2023; 382:81-87. [PMID: 37797004 DOI: 10.1126/science.adf2040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Accepted: 08/30/2023] [Indexed: 10/07/2023]
Abstract
For almost a century, magnetic oscillations have been a powerful "quantum ruler" for measuring Fermi surface topology. In this study, we used Landau-level spectroscopy to unravel the energy-resolved valley-contrasting orbital magnetism and large orbital magnetic susceptibility that contribute to the energies of Landau levels of twisted double-bilayer graphene. These orbital magnetism effects led to substantial deviations from the standard Onsager relation, which manifested as a breakdown in scaling of Landau-level orbits. These substantial magnetic responses emerged from the nontrivial quantum geometry of the electronic structure and the large length scale of the moiré lattice potential. Going beyond traditional measurements, Landau-level spectroscopy performed with a scanning tunneling microscope offers a complete quantum ruler that resolves the full energy dependence of orbital magnetic properties in moiré quantum matter.
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Affiliation(s)
- M R Slot
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
- Department of Physics, Georgetown University, Washington, DC 20007, USA
| | - Y Maximenko
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA
| | - P M Haney
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - S Kim
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
- Joint Quantum Institute, Department of Physics, University of Maryland, College Park, MD 20742, USA
| | - D T Walkup
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - E Strelcov
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA
| | - Son T Le
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - E M Shih
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA
| | - D Yildiz
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
- Joint Quantum Institute, Department of Physics, University of Maryland, College Park, MD 20742, USA
| | - S R Blankenship
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - K Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - T Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Y Barlas
- Department of Physics, University of Nevada, Reno, NV 89557, USA
| | - N B Zhitenev
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - F Ghahari
- Department of Physics and Astronomy, George Mason University, Fairfax, VA 22030, USA
| | - J A Stroscio
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
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Zhitenev NB, Sidorenko A, Tennant DM, Cirelli RA. Chemical modification of the electronic conducting states in polymer nanodevices. Nat Nanotechnol 2007; 2:237-242. [PMID: 18654269 DOI: 10.1038/nnano.2007.75] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2006] [Accepted: 02/27/2007] [Indexed: 05/26/2023]
Abstract
Organic materials offer new electronic functionality not available in inorganic devices. However, the integration of organic compounds within nanoscale electronic circuitry poses new challenges for materials physics and chemistry. Typically, the electronic states in organic materials are energetically misaligned with the Fermi level of metal contacts. Here, we study the voltage-induced change in conductivity in nanoscale devices comprising a monolayer of polyelectrolyte macromolecules. The devices are fabricated using integrated shadow masks. Reversible switching is observed between conducting (ON) and non-conducting (OFF) states in the devices. The open design of our devices easily permits chemical modification of the polyelectrolyte, which we show has a pronounced effect on the ON-OFF switching. We suggest that the switching voltage ionizes the polymers, creating a conducting channel of electronic levels aligned with the contact Fermi level.
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Affiliation(s)
- N B Zhitenev
- Bell Labs, Alcatel-Lucent, 600 Mountain Avenue, Murray Hill, New Jersey 07974, USA.
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Zhitenev NB, Erbe A, Bao Z. Single- and multigrain nanojunctions with a self-assembled monolayer of conjugated molecules. Phys Rev Lett 2004; 92:186805. [PMID: 15169523 DOI: 10.1103/physrevlett.92.186805] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2003] [Indexed: 05/24/2023]
Abstract
Systematic conductivity measurements in nanoscale junctions containing a self-assembled monolayer of conjugated molecules are reported. Different conductivity mechanisms are identified depending on the granularity of the metal used as a substrate for assembling the monolayer. Unexpectedly, the energy scale controlling the dominant conductance channels is quite low in comparison with the molecular level spacing. In single-grain junctions, the dominant conductance mechanism is hopping with an energy scale of the order of 10-100 meV determined by the nature of the metal contacts. In the case of multigrain junctions, additional tunnel conductance is observed with low-energy Coulomb-blockade features.
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Affiliation(s)
- N B Zhitenev
- Bell Labs, Lucent Technologies, Murray Hill, NJ 07974, USA
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Abstract
A new method of fabricating small metal-molecule-metal junctions is developed, approaching the single-molecule limit. The conductance of different conjugated molecules in a broad temperature, source-drain, and gate voltage regime is reported. At low temperature, all investigated molecules display sharp conductance steps periodic in source-drain voltage. The position of these steps can be controlled by a gate potential. The spacing corresponds to the energy of the lowest molecular vibrations. These results show that the low-bias conductance of molecules is dominated by resonant tunneling through coupled electronic and vibration levels.
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Affiliation(s)
- N B Zhitenev
- Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974, USA
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Brodsky M, Zhitenev NB, Ashoori RC, Pfeiffer LN, West KW. Localization in artificial disorder: two coupled quantum dots. Phys Rev Lett 2000; 85:2356-2359. [PMID: 10978009 DOI: 10.1103/physrevlett.85.2356] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2000] [Indexed: 05/23/2023]
Abstract
Using single electron capacitance spectroscopy, we study electron additions in quantum dots containing two potential minima separated by a shallow barrier. Analysis of the addition spectra in the magnetic field allows us to distinguish between electrons delocalized over the entire dot and those localized in either of the potential minima. We demonstrate that a high magnetic field abruptly splits up a low-density droplet into two smaller fragments, each residing in a potential minimum. An unexplained cancellation of electron repulsion between electrons in these fragments gives rise to paired electron additions.
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Affiliation(s)
- M Brodsky
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Abstract
Single-electron capacitance spectroscopy precisely measures the energies required to add individual electrons to a quantum dot. The spatial extent of electronic wave functions is probed by investigating the dependence of these energies on changes in the dot confining potential. For low electron densities, electrons occupy distinct spatial sites localized within the dot. At higher densities, the electrons become delocalized, and all wave functions are spread over the full dot area. Near the delocalization transition, the last remaining localized states exist at the perimeter of the dot. Unexpectedly, these electrons appear to bind with electrons in the dot center.
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Affiliation(s)
- NB Zhitenev
- Department of Physics and Center for Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. Bell Laboratories, Lucent Technologies, Murray Hill, NJ 07974, USA
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