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Reddy AP, Devakul T, Fu L. Artificial Atoms, Wigner Molecules, and an Emergent Kagome Lattice in Semiconductor Moiré Superlattices. PHYSICAL REVIEW LETTERS 2023; 131:246501. [PMID: 38181155 DOI: 10.1103/physrevlett.131.246501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 11/18/2023] [Indexed: 01/07/2024]
Abstract
Semiconductor moiré superlattices comprise an array of artificial atoms and provide a highly tunable platform for exploring novel electronic phases. We introduce a theoretical framework for studying moiré quantum matter that treats intra-moiré-atom interactions exactly and is controlled in the limit of large moiré period. We reveal an abundance of new physics arising from strong electron interactions when there are multiple electrons within a moiré unit cell. In particular, at filling factor n=3, the Coulomb interaction within each three-electron moiré atom leads to a three-lobed "Wigner molecule." When their size is comparable to the moiré period, the Wigner molecules form an emergent Kagome lattice. Our Letter identifies two universal length scales characterizing the kinetic and interaction energies in moiré materials and demonstrates a rich phase diagram due to their interplay.
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Affiliation(s)
- Aidan P Reddy
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Trithep Devakul
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Liang Fu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Corrigan J, Dodson JP, Ercan HE, Abadillo-Uriel JC, Thorgrimsson B, Knapp TJ, Holman N, McJunkin T, Neyens SF, MacQuarrie ER, Foote RH, Edge LF, Friesen M, Coppersmith SN, Eriksson MA. Coherent Control and Spectroscopy of a Semiconductor Quantum Dot Wigner Molecule. PHYSICAL REVIEW LETTERS 2021; 127:127701. [PMID: 34597063 DOI: 10.1103/physrevlett.127.127701] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 07/19/2021] [Indexed: 06/13/2023]
Abstract
Semiconductor quantum dots containing more than one electron have found wide application in qubits, where they enable readout and enhance polarizability. However, coherent control in such dots has typically been restricted to only the lowest two levels, and such control in the strongly interacting regime has not been realized. Here we report quantum control of eight different transitions in a silicon-based quantum dot. We use qubit readout to perform spectroscopy, revealing a dense set of energy levels with characteristic spacing far smaller than the single-particle energy. By comparing with full configuration interaction calculations, we argue that the dense set of levels arises from Wigner-molecule physics.
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Affiliation(s)
- J Corrigan
- University of Wisconsin, Madison, Wisconsin 53706, USA
| | - J P Dodson
- University of Wisconsin, Madison, Wisconsin 53706, USA
| | - H Ekmel Ercan
- University of Wisconsin, Madison, Wisconsin 53706, USA
| | | | | | - T J Knapp
- University of Wisconsin, Madison, Wisconsin 53706, USA
| | - Nathan Holman
- University of Wisconsin, Madison, Wisconsin 53706, USA
| | | | | | | | - Ryan H Foote
- University of Wisconsin, Madison, Wisconsin 53706, USA
| | - L F Edge
- HRL Laboratories, LLC, 3011 Malibu Canyon Road, Malibu, California 90265, USA
| | - Mark Friesen
- University of Wisconsin, Madison, Wisconsin 53706, USA
| | - S N Coppersmith
- University of Wisconsin, Madison, Wisconsin 53706, USA
- University of New South Wales, Sydney, NSW 2052, Australia
| | - M A Eriksson
- University of Wisconsin, Madison, Wisconsin 53706, USA
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Cavaliere F, Gambetta FM, Ziani NT, Sassetti M. Current noise as a probe for Wigner molecules. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:425301. [PMID: 26416613 DOI: 10.1088/0953-8984/27/42/425301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The effects of a Wigner molecule on the current noise and conductance of a one-dimensional quantum dot with two electrons are investigated. Focusing on a lateral transport setup, the sequential regime is considered. Tunnelling rates through the dot are evaluated within an exact diagonalisation scheme. They strongly depend on electron interactions, showing a markedly different behaviour in the presence of a Wigner molecule with respect to the weak interactions case, and thus modify the transport and current noise and the dot. For weak interactions negative differential conductance and super-Poissonian noise are found. As interactions increase, a Wigner molecule develops: it suppresses the negative differential conductance and turns the shot noise to sub-Poissonian values. In particular, the noise is found to be a sensitive probe of the Wigner molecule.
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Affiliation(s)
- F Cavaliere
- Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146 Genova, Italy. SPIN-CNR, Via Dodecaneso 33, 16146 Genova, Italy
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Cavaliere F, Ziani NT, Negro F, Sassetti M. Thermally enhanced Wigner oscillations in two-electron 1D quantum dots. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:505301. [PMID: 25419598 DOI: 10.1088/0953-8984/26/50/505301] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Motivated by a recent experiment (Pecker et al 2013 Nat. Phys. 9 576), we study the stability, with respect to thermal effects, of Friedel and Wigner density fluctuations for two electrons trapped in a one-dimensional quantum dot. Diagonalizing the system exactly, the finite-temperature average electron density is computed. While the weak and strong interaction regimes display a Friedel oscillation or a Wigner molecule state at zero temperature, which as expected smear and melt as the temperature increases, a peculiar thermal enhancement of Wigner correlations in the intermediate interaction regime is found. We demonstrate that this effect is due to the presence of two different characteristic temperature scales: T(F), dictating the smearing of Friedel oscillations, and T(W), smoothing Wigner oscillations. In the early Wigner molecule regime, for intermediate interactions, T(F) < T(W) leading to the enhancement of the visibility of Wigner oscillations. These results complement those obtained within the Luttinger liquid picture, valid for larger numbers of particles.
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Affiliation(s)
- F Cavaliere
- Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146 Genova, Italy. CNR-SPIN, Via Dodecaneso 33, 16146 Genova, Italy
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