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How to Recognize the Universal Aspects of Mott Criticality? CRYSTALS 2022. [DOI: 10.3390/cryst12070932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In this paper we critically discuss several examples of two-dimensional electronic systems displaying interaction-driven metal-insulator transitions of the Mott (or Wigner–Mott) type, including dilute two-dimension electron gases (2DEG) in semiconductors, Mott organic materials, as well as the recently discovered transition-metal dichalcogenide (TMD) moiré bilayers. Remarkably similar behavior is found in all these systems, which is starting to paint a robust picture of Mott criticality. Most notable, on the metallic side a resistivity maximum is observed whose temperature scale vanishes at the transition. We compare the available experimental data on these systems to three existing theoretical scenarios: spinon theory, Dynamical Mean Field Theory (DMFT) and percolation theory. We show that the DMFT and percolation pictures for Mott criticality can be distinguished by studying the origins of the resistivity maxima using an analysis of the dielectric response.
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Spin effect on the low-temperature resistivity maximum in a strongly interacting 2D electron system. Sci Rep 2022; 12:5080. [PMID: 35332223 PMCID: PMC8948273 DOI: 10.1038/s41598-022-09034-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Accepted: 03/16/2022] [Indexed: 11/08/2022] Open
Abstract
The increase in the resistivity with decreasing temperature followed by a drop by more than one order of magnitude is observed on the metallic side near the zero-magnetic-field metal-insulator transition in a strongly interacting two-dimensional electron system in ultra-clean SiGe/Si/SiGe quantum wells. We find that the temperature [Formula: see text], at which the resistivity exhibits a maximum, is close to the renormalized Fermi temperature. However, rather than increasing along with the Fermi temperature, the value [Formula: see text] decreases appreciably for spinless electrons in spin-polarizing (parallel) magnetic fields. The observed behaviour of [Formula: see text] cannot be described by existing theories. The results indicate the spin-related origin of the effect.
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Stanley LJ, Chuang HJ, Zhou Z, Koehler MR, Yan J, Mandrus DG, Popović D. Low-Temperature 2D/2D Ohmic Contacts in WSe 2 Field-Effect Transistors as a Platform for the 2D Metal-Insulator Transition. ACS APPLIED MATERIALS & INTERFACES 2021; 13:10594-10602. [PMID: 33617715 DOI: 10.1021/acsami.0c21440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We report the fabrication of hexagonal-boron-nitride (hBN) encapsulated multiterminal WSe2 Hall bars with 2D/2D low-temperature Ohmic contacts as a platform for investigating the two-dimensional (2D) metal-insulator transition. We demonstrate that the WSe2 devices exhibit Ohmic behavior down to 0.25 K and at low enough excitation voltages to avoid current-heating effects. Additionally, the high-quality hBN-encapsulated WSe2 devices in ideal Hall-bar geometry enable us to accurately determine the carrier density. Measurements of the temperature (T) and density (ns) dependence of the conductivity σ(T, ns) demonstrate scaling behavior consistent with a metal-insulator quantum phase transition driven by electron-electron interactions but where disorder-induced local magnetic moments are also present. Our findings pave the way for further studies of the fundamental quantum mechanical properties of 2D transition metal dichalcogenides using the same contact engineering.
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Affiliation(s)
- Lily J Stanley
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States
- Department of Physics, Florida State University, Tallahassee, Florida 32306, United States
| | - Hsun-Jen Chuang
- Physics and Astronomy Department, Wayne State University, Detroit, Michigan 48202, United States
| | - Zhixian Zhou
- Physics and Astronomy Department, Wayne State University, Detroit, Michigan 48202, United States
| | - Michael R Koehler
- Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Jiaqiang Yan
- Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee 37996, United States
- Oak Ridge National Lab, Oak Ridge, Tennessee 37830, United States
| | - David G Mandrus
- Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee 37996, United States
- Oak Ridge National Lab, Oak Ridge, Tennessee 37830, United States
| | - Dragana Popović
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States
- Department of Physics, Florida State University, Tallahassee, Florida 32306, United States
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Recent Developments in the Field of the Metal-Insulator Transition in Two Dimensions. APPLIED SCIENCES-BASEL 2019. [DOI: 10.3390/app9061169] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We review the latest developments in the field of the metal-insulator transition in strongly-correlated two-dimensional electron systems. Particular attention is given to recent discoveries of a sliding quantum electron solid and interaction-induced spectrum flattening at the Fermi level in high-quality silicon-based structures.
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Transport evidence for a sliding two-dimensional quantum electron solid. Nat Commun 2018; 9:3803. [PMID: 30228256 PMCID: PMC6143544 DOI: 10.1038/s41467-018-06332-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Accepted: 08/22/2018] [Indexed: 11/08/2022] Open
Abstract
Ignited by the discovery of the metal-insulator transition, the behaviour of low-disorder two-dimensional (2D) electron systems is currently the focus of a great deal of attention. In the strongly interacting limit, electrons are expected to crystallize into a quantum Wigner crystal, but no definitive evidence for this effect has been obtained despite much experimental effort over the years. Here, studying the insulating state of a 2D electron system in silicon, we have found two-threshold voltage-current characteristics with a dramatic increase in noise between the two threshold voltages. This behaviour cannot be described within existing traditional models. On the other hand, it is strikingly similar to that observed for the collective depinning of the vortex lattice in type-II superconductors. Adapting the model used for vortexes to the case of an electron solid yields good agreement with our experimental results, favouring the quantum electron solid as the origin of the low-density state.
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Lin PV, Popović D. Critical Behavior of a Strongly Disordered 2D Electron System: The Cases of Long-Range and Screened Coulomb Interactions. PHYSICAL REVIEW LETTERS 2015; 114:166401. [PMID: 25955059 DOI: 10.1103/physrevlett.114.166401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Indexed: 06/04/2023]
Abstract
A study of the temperature (T) and density (ns) dependence of conductivity σ(ns,T) of a highly disordered, two-dimensional (2D) electron system in Si demonstrates scaling behavior consistent with the existence of a metal-insulator transition (MIT). The same critical exponents are found when the Coulomb interaction is screened by the metallic gate and when it is unscreened or long range. The results strongly suggest the existence of a disorder-dominated 2D MIT, which is not directly affected by the range of the Coulomb interactions.
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Affiliation(s)
- Ping V Lin
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA
| | - Dragana Popović
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA
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Takashina K, Niida Y, Renard VT, Fujiwara A, Fujisawa T, Muraki K, Hirayama Y. Impact of valley polarization on the resistivity in two dimensions. PHYSICAL REVIEW LETTERS 2011; 106:196403. [PMID: 21668179 DOI: 10.1103/physrevlett.106.196403] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Indexed: 05/30/2023]
Abstract
We examine the temperature dependence of resistivity in a two-dimensional electron system formed in a silicon-on-insulator quantum well. The device allows us to tune the valley splitting continuously in addition to the electron density. Our data provide a global picture of how the resistivity and its temperature dependence change with valley polarization. At the boundary between valley-polarized and partially polarized regions, we demonstrate that there is an insulating contribution from spin-degenerate electrons occupying the upper valley-subband edge.
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Affiliation(s)
- K Takashina
- Department of Physics, University of Bath, Bath BA2 7AY, United Kingdom
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Shashkin AA, Anissimova S, Sakr MR, Kravchenko SV, Dolgopolov VT, Klapwijk TM. Pauli spin susceptibility of a strongly correlated two-dimensional electron liquid. PHYSICAL REVIEW LETTERS 2006; 96:036403. [PMID: 16486743 DOI: 10.1103/physrevlett.96.036403] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2005] [Indexed: 05/06/2023]
Abstract
Thermodynamic measurements reveal that the Pauli spin susceptibility of strongly correlated two-dimensional electrons in silicon grows critically at low electron densities--behavior that is characteristic of the existence of a phase transition.
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Affiliation(s)
- A A Shashkin
- Physics Department, Northeastern University, Boston, Massachusetts 02115, USA
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Jaroszyński J, Popović D, Klapwijk TM. Magnetic-field dependence of the anomalous noise behavior in a two-dimensional electron system in silicon. PHYSICAL REVIEW LETTERS 2004; 92:226403. [PMID: 15245243 DOI: 10.1103/physrevlett.92.226403] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2003] [Indexed: 05/24/2023]
Abstract
Studies of low-frequency resistance noise show that the dramatic change in the dynamics of the two-dimensional electron system (2DES) in Si that occurs near the metal-insulator transition (MIT) persists in high parallel magnetic fields B such that the 2DES is fully spin polarized. This strongly suggests that charge, as opposed to spin, degrees of freedom are responsible for this effect. In the metallic phase, however, noise is suppressed by a parallel B, pointing to the role of spins. At low B, the temperature dependence of conductivity in the metallic phase provides evidence for a MIT.
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Affiliation(s)
- J Jaroszyński
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA.
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Denteneer PJH, Scalettar RT. Interacting electrons in a two-dimensional disordered environment: effect of a zeeman magnetic field. PHYSICAL REVIEW LETTERS 2003; 90:246401. [PMID: 12857206 DOI: 10.1103/physrevlett.90.246401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2003] [Indexed: 05/24/2023]
Abstract
The effect of a Zeeman magnetic field coupled to the spin of the electrons on the conducting properties of the disordered Hubbard model is studied. Using the determinant quantum Monte Carlo method, the temperature- and magnetic-field-dependent conductivity is calculated, as well as the degree of spin polarization. We find that the Zeeman magnetic field suppresses the metallic behavior present for certain values of interaction and disorder strength and is able to induce a metal-insulator transition at a critical field strength. It is argued that the qualitative features of magnetoconductance in this microscopic model containing both repulsive interactions and disorder are in agreement with experimental findings in two-dimensional electron and hole gases in semiconductor structures.
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Affiliation(s)
- P J H Denteneer
- Lorentz Institute, Leiden University, PO Box 9506, 2300 RA Leiden, The Netherlands
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Leturcq R, L'Hôte D, Tourbot R, Mellor CJ, Henini M. Resistance noise scaling in a dilute two-dimensional hole system in GaAs. PHYSICAL REVIEW LETTERS 2003; 90:076402. [PMID: 12633254 DOI: 10.1103/physrevlett.90.076402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2002] [Indexed: 05/24/2023]
Abstract
We have measured the resistance noise of a two-dimensional (2D) hole system in a high mobility GaAs quantum well, around the 2D metal-insulator transition (MIT) at zero magnetic field. The normalized noise power S(R)/R(2) increases strongly when the hole density p(s) is decreased, increases slightly with temperature (T) at the largest densities, and decreases strongly with T at low p(s). The noise scales with the resistance, S(R)/R(2) approximately R2.4, as for a second order phase transition such as a percolation transition. The p(s) dependence of the conductivity is consistent with a critical behavior for such a transition, near a density p(*) which is lower than the observed MIT critical density p(c).
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Affiliation(s)
- R Leturcq
- Service de Physique de l'Etat Condensé, CEA/DSM, CE Saclay, F-91191 Gif-sur-Yvette, France
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Jaroszyński J, Popović D, Klapwijk TM. Universal behavior of the resistance noise across the metal-insulator transition in silicon inversion layers. PHYSICAL REVIEW LETTERS 2002; 89:276401. [PMID: 12513226 DOI: 10.1103/physrevlett.89.276401] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2002] [Indexed: 05/24/2023]
Abstract
Studies of low-frequency resistance noise show that the glassy freezing of the two-dimensional (2D) electron system in the vicinity of the metal-insulator transition occurs in all Si inversion layers. The size of the metallic glass phase, which separates the 2D metal and the (glassy) insulator, depends strongly on disorder, becoming extremely small in high-mobility samples. The behavior of the second spectrum, an important fourth-order noise statistic, indicates the presence of long-range correlations between fluctuators in the glassy phase, consistent with the hierarchical picture of glassy dynamics.
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Affiliation(s)
- J Jaroszyński
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA
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Bogdanovich S, Popović D. Onset of glassy dynamics in a two-dimensional electron system in silicon. PHYSICAL REVIEW LETTERS 2002; 88:236401. [PMID: 12059382 DOI: 10.1103/physrevlett.88.236401] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2001] [Indexed: 05/23/2023]
Abstract
The fluctuations of conductivity sigma with time have been studied in a two-dimensional electron system in low-mobility Si inversion layers. The noise power spectrum is approximately 1/f(alpha) with alpha exhibiting a sharp jump at an electron density n(s) = n(g). A huge increase in the relative variance of sigma is observed as n(s) is reduced below n(g), reflecting a dramatic slowing down of the electron dynamics. This is attributed to the freezing of the electron glass. The data strongly suggest that glassy dynamics persists in the metallic phase.
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Affiliation(s)
- Snezana Bogdanovich
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA
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Eng K, Feng XG, Popović D, Washburn S. Effects of a parallel magnetic field on the metal-insulator transition in a dilute two-dimensional electron system. PHYSICAL REVIEW LETTERS 2002; 88:136402. [PMID: 11955112 DOI: 10.1103/physrevlett.88.136402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2001] [Indexed: 05/23/2023]
Abstract
The temperature dependence of conductivity sigma(T) of a two-dimensional electron system in silicon has been studied in parallel magnetic fields B. At B = 0, the system displays a metal-insulator transition at a critical electron density n(c)(0), and dsigma/dT>0 in the metallic phase. At low fields ( B < or approximately equal to 2 T), n(c) increases as n(c)(B)-n(c)(0) proportional, variant Bbeta ( beta approximately 1), and the zero-temperature conductivity scales as sigma(n(s),B,T = 0)/sigma(n(s),0,0) = f(B(beta)/delta(n)), where delta(n) = [n(s)-n(c)(0)]/n(c)(0) and n(s) is electron density, as expected for a quantum phase transition. The metallic phase persists in fields of up to 18 T, consistent with the saturation of n(c) at high fields.
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Affiliation(s)
- Kevin Eng
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA
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