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Deng H, Pfeiffer LN, West KW, Baldwin KW, Engel LW, Shayegan M. Probing the Melting of a Two-Dimensional Quantum Wigner Crystal via its Screening Efficiency. PHYSICAL REVIEW LETTERS 2019; 122:116601. [PMID: 30951347 DOI: 10.1103/physrevlett.122.116601] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Indexed: 06/09/2023]
Abstract
One of the most fundamental and yet elusive collective phases of an interacting electron system is the quantum Wigner crystal (WC), an ordered array of electrons expected to form when the electrons' Coulomb repulsion energy eclipses their kinetic (Fermi) energy. In low-disorder, two-dimensional (2D) electron systems, the quantum WC is known to be favored at very low temperatures (T) and small Landau level filling factors (ν), near the termination of the fractional quantum Hall states. This WC phase exhibits an insulating behavior, reflecting its pinning by the small but finite disorder potential. An experimental determination of a T vs ν phase diagram for the melting of the WC, however, has proved to be challenging. Here we use capacitance measurements to probe the 2D WC through its effective screening as a function of T and ν. We find that, as expected, the screening efficiency of the pinned WC is very poor at very low T and improves at higher T once the WC melts. Surprisingly, however, rather than monotonically changing with increasing T, the screening efficiency shows a well-defined maximum at a T that is close to the previously reported melting temperature of the WC. Our experimental results suggest a new method to map out a T vs ν phase diagram of the magnetic-field-induced WC precisely.
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Affiliation(s)
- H Deng
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544-5263, USA
| | - L N Pfeiffer
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544-5263, USA
| | - K W West
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544-5263, USA
| | - K W Baldwin
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544-5263, USA
| | - L W Engel
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, USA
| | - M Shayegan
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544-5263, USA
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Nasyedkin K, Byeon H, Zhang L, Beysengulov NR, Milem J, Hemmerle S, Loloee R, Pollanen J. Unconventional field-effect transistor composed of electrons floating on liquid helium. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:465501. [PMID: 30280700 DOI: 10.1088/1361-648x/aae5ef] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We report on an unconventional macroscopic field effect transistor composed of electrons floating above the surface of superfluid helium. With this device unique transport regimes are realized in which the charge density of the electron layer can be controlled in a manner not possible in other material systems. In particular, we are able to manipulate the collective behavior of the electrons to produce a highly non-uniform, but precisely controlled, charge density to reveal a negative source-drain current. This behavior can be understood by considering the propagation of damped charge oscillations along a transmission line formed by the inhomogeneous sheet of two-dimensional electrons above, and between, the source and drain electrodes of the transistor.
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Affiliation(s)
- K Nasyedkin
- Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824-2320, United States of America
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3
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New Reentrant Insulating Phases in Strongly Interacting 2D Systems with Low Disorder. APPLIED SCIENCES-BASEL 2018. [DOI: 10.3390/app8101909] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The metal-insulator transition (MIT) in two-dimension (2D) was discovered by Kravchenko et al. more than two decades ago in strongly interacting 2D electrons residing in a Si-metal-oxide-semiconductor field-effect transistor (Si-MOSFET). Its origin remains unresolved. Recently, low magnetic field reentrant insulating phases (RIPs), which dwell between the zero-field (B = 0) metallic state and the integer quantum Hall (QH) states where the Landau-level filling factor υ > 1, have been observed in strongly correlated 2D GaAs hole systems with a large interaction parameter, rs, (~20–40) and a high purity. A new complex phase diagram was proposed, which includes zero-field MIT, low magnetic field RIPs, integer QH states, fractional QH states, high field RIPs and insulating phases (HFIPs) with υ < 1 in which the insulating phases are explained by the formation of a Wigner crystal. Furthermore, evidence of new intermediate phases was reported. This review article serves the purpose of summarizing those recent experimental findings and theoretical endeavors to foster future research efforts.
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Belitz D, Kirkpatrick TR. Scaling Theory of a Compressibility-Driven Metal-Insulator Transition in a Two-Dimensional Electron Fluid. PHYSICAL REVIEW LETTERS 2016; 117:236803. [PMID: 27982611 DOI: 10.1103/physrevlett.117.236803] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Indexed: 06/06/2023]
Abstract
We present a scaling description of a metal-insulator transition in two-dimensional electron systems that is driven by a vanishing compressibility rather than a vanishing diffusion coefficient. A small set of basic assumptions leads to a consistent theoretical framework that is compatible with existing transport and compressibility measurements, and allows us to make predictions for other observables. We also discuss connections between these ideas and other theories of transitions to an incompressible quantum fluid.
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Affiliation(s)
- D Belitz
- Department of Physics, Institute of Theoretical Science, and Materials Science Institute, University of Oregon, Eugene, Oregon 97403, USA
| | - T R Kirkpatrick
- Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA
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Kumar N, Kitoh A, Inoue IH. Anomalous enhancement of the sheet carrier density beyond the classic limit on a SrTiO3 surface. Sci Rep 2016; 6:25789. [PMID: 27174141 PMCID: PMC4865841 DOI: 10.1038/srep25789] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 04/22/2016] [Indexed: 11/28/2022] Open
Abstract
Electrostatic carrier accumulation on an insulating (100) surface of SrTiO3 by fabricating a field effect transistor with Parylene-C (6 nm)/HfO2 (20 nm) bilayer gate insulator has revealed a mystifying phenomenon: sheet carrier density is about 10 times as large as ( is the sheet capacitance of the gate insulator, VG is the gate voltage, and e is the elementary charge). The channel is so clean to exhibit small subthreshod swing of 170 mV/decade and large mobility of 11 cm2/Vs for of 1 × 1014 cm−2 at room temperature. Since does not depend on either VG nor time duration, beyond is solely ascribed to negative charge compressibility of the carriers, which was in general considered as due to exchange interactions among electrons in the small limit. However, the observed is too large to be naively understood by the framework. Alternative ideas are proposed in this work.
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Affiliation(s)
- Neeraj Kumar
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565, Japan
| | - Ai Kitoh
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565, Japan
| | - Isao H Inoue
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565, Japan
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6
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Strongly correlated two-dimensional plasma explored from entropy measurements. Nat Commun 2015; 6:7298. [DOI: 10.1038/ncomms8298] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Accepted: 04/27/2015] [Indexed: 11/09/2022] Open
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Qiu RLJ, Gao XPA, Pfeiffer LN, West KW. Connecting the reentrant insulating phase and the zero-field metal-insulator transition in a 2D hole system. PHYSICAL REVIEW LETTERS 2012; 108:106404. [PMID: 22463433 DOI: 10.1103/physrevlett.108.106404] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Indexed: 05/31/2023]
Abstract
We present the transport and capacitance measurements of 10 nm wide GaAs quantum wells with hole densities around the critical point of the 2D metal-insulator transition (critical density p(c) down to 0.8 × 10(10)/cm2, r(s) ∼ 36). For metallic hole density p(c) < p < p(c) + 0.15 × 10(10)/cm2, a reentrant insulating phase (RIP) is observed between the ν = 1 quantum Hall state and the zero-field metallic state and it is attributed to the formation of pinned Wigner crystal. Through studying the evolution of the RIP versus 2D hole density, we show that the RIP is incompressible and continuously connected to the zero-field insulator, suggesting a similar origin for these two phases.
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Affiliation(s)
- R L J Qiu
- Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106, USA
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Jiang Y, Qi Q, Wang R, Zhang J, Xue Q, Wang C, Jiang C, Qiu X. Direct observation and measurement of mobile charge carriers in a monolayer organic semiconductor on a dielectric substrate. ACS NANO 2011; 5:6195-6201. [PMID: 21740011 DOI: 10.1021/nn200760r] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We report the electrical characterization of a single layer of an organic semiconductor grown on a dielectric surface. The dynamic response of the charge carriers in the monolayer film of pentacene was characterized through the electrostatic interactions between an electric force microscope (EFM) probe and pentacene islands of various sizes. These islands were formed in situ by segmenting a coalesced pentacene monolayer into separated regions. The size-dependent dielectric responses of the pentacene islands suggest that mobile charges exist in the organic monolayer. Local capacitance spectroscopy revealed that the charge carriers in the p-type pentacene monolayer could be depleted at high bias voltages, enabling a further determination of the charge-carrier concentration in the organic semiconductor ultrathin film.
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Affiliation(s)
- Yeping Jiang
- National Center for Nanoscience and Technology, Beijing 100190, China
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Li L, Richter C, Paetel S, Kopp T, Mannhart J, Ashoori RC. Very large capacitance enhancement in a two-dimensional electron system. Science 2011; 332:825-8. [PMID: 21566188 DOI: 10.1126/science.1204168] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Increases in the gate capacitance of field-effect transistor structures allow the production of lower-power devices that are compatible with higher clock rates, driving the race for developing high-κ dielectrics. However, many-body effects in an electronic system can also enhance capacitance. Onto the electron system that forms at the LaAlO(3)/SrTiO(3) interface, we fabricated top-gate electrodes that can fully deplete the interface of all mobile electrons. Near depletion, we found a greater than 40% enhancement of the gate capacitance. Using an electric-field penetration measurement method, we show that this capacitance originates from a negative compressibility of the interface electron system. Capacitance enhancement exists at room temperature and arises at low electron densities, in which disorder is strong and the in-plane conductance is much smaller than the quantum conductance.
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Affiliation(s)
- Lu Li
- Department of Physics, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139, USA
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Risović D, Frka S, Kozarac Z. Application of Brewster angle microscopy and fractal analysis in investigations of compressibility of Langmuir monolayers. J Chem Phys 2011; 134:024701. [DOI: 10.1063/1.3522646] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Cugliandolo LF, Giamarchi T, Doussal PL. Dynamic compressibility and aging in Wigner crystals and quantum glasses. PHYSICAL REVIEW LETTERS 2006; 96:217203. [PMID: 16803271 DOI: 10.1103/physrevlett.96.217203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2005] [Indexed: 05/10/2023]
Abstract
We study the nonequilibrium linear response of quantum elastic systems pinned by quenched disorder with Schwinger-Keldysh real-time techniques complemented by a mean-field variational approach. We find (i) a quasiequilibrium regime in which the analytic continuation from the imaginary-time replica results holds provided the marginality condition is enforced, and (ii) an aging regime. The conductivity and compressibility are computed. The latter is found to cross over from its dynamic to static value on a scale set by the waiting time after a quench, an effect which can be probed in experiments in, e.g., Wigner glasses.
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Affiliation(s)
- Leticia F Cugliandolo
- Laboratoire de Physique Théorique et Hautes Energies, 4 Place Jussieu, 75252 Paris Cedex 05, France
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Allison G, Galaktionov EA, Savchenko AK, Safonov SS, Fogler MM, Simmons MY, Ritchie DA. Thermodynamic density of states of two-dimensional GaAs systems near the apparent metal-insulator transition. PHYSICAL REVIEW LETTERS 2006; 96:216407. [PMID: 16803263 DOI: 10.1103/physrevlett.96.216407] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2005] [Indexed: 05/10/2023]
Abstract
We perform combined resistivity and compressibility studies of two-dimensional hole and electron systems which show the apparent metal-insulator transition--a crossover in the sign of deltaR/deltaT with changing density. No thermodynamic anomalies have been detected in the crossover region. Instead, despite a tenfold difference in r(s), the compressibility of both electrons and holes is well described by the theory of nonlinear screening of the random potential. We show that the resistivity exhibits a scaling behavior near the percolation threshold found from analysis of the compressibility. Notably, the percolation transition occurs at a much lower density than the crossover.
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Affiliation(s)
- G Allison
- School of Physics, University of Exeter, Exeter EX4 4QL, United Kingdom
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13
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Punnoose A, Finkel'stein AM. Metal-Insulator Transition in Disordered Two-Dimensional Electron Systems. Science 2005; 310:289-91. [PMID: 16224015 DOI: 10.1126/science.1115660] [Citation(s) in RCA: 220] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
We present a theory of the metal-insulator transition in a disordered two-dimensional electron gas. A quantum critical point, separating the metallic phase, which is stabilized by electronic interactions, from the insulating phase, where disorder prevails over the electronic interactions, has been identified. The existence of the quantum critical point leads to a divergence in the density of states of the underlying collective modes at the transition, causing the thermodynamic properties to behave critically as the transition is approached. We show that the interplay of electron-electron interactions and disorder can explain the observed transport properties and the anomalous enhancement of the spin susceptibility near the metal-insulator transition.
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14
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Das Sarma S, Lilly MP, Hwang EH, Pfeiffer LN, West KW, Reno JL. Two-dimensional metal-insulator transition as a percolation transition in a high-mobility electron system. PHYSICAL REVIEW LETTERS 2005; 94:136401. [PMID: 15904007 DOI: 10.1103/physrevlett.94.136401] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2004] [Indexed: 05/02/2023]
Abstract
By carefully analyzing the low temperature density dependence of 2D conductivity in undoped high-mobility n-GaAs heterostructures, we conclude that the 2D metal-insulator transition in this 2D electron system is a density inhomogeneity driven percolation transition due to the breakdown of screening in the random charged impurity disorder background. In particular, our measured conductivity exponent of approximately 1.4 approaches the 2D percolation exponent value of 4/3 at low temperatures and our experimental data are inconsistent with there being a zero-temperature quantum critical point in our system.
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Affiliation(s)
- S Das Sarma
- Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
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Shi J, Xie XC. Droplet state and the compressibility anomaly in dilute 2D electron systems. PHYSICAL REVIEW LETTERS 2002; 88:086401. [PMID: 11863965 DOI: 10.1103/physrevlett.88.086401] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2001] [Indexed: 05/23/2023]
Abstract
We investigate the space distribution of carrier density and the compressibility of two-dimensional (2D) electron systems by using the local density approximation. The strong correlation is simulated by the local exchange and correlation energies. A slowly varied disorder potential is applied to simulate the disorder effect. We show that the compressibility anomaly observed in 2D systems which accompanies the metal-insulator transition can be attributed to the formation of the droplet state due to a disorder effect at low carrier densities.
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Affiliation(s)
- Junren Shi
- Department of Physics, Oklahoma State University, Stillwater, Oklahoma 74078, USA
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Ilani S, Yacoby A, Mahalu D, Shtrikman H. Microscopic Structure of the Metal-Insulator Transition in Two Dimensions. Science 2001; 292:1354-7. [PMID: 11359006 DOI: 10.1126/science.1058645] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
A single electron transistor is used as a local electrostatic probe to study the underlying spatial structure of the metal-insulator transition in two dimensions. The measurements show that as we approach the transition from the metallic side, a new phase emerges that consists of weakly coupled fragments of the two-dimensional system. These fragments consist of localized charge that coexists with the surrounding metallic phase. As the density is lowered into the insulating phase, the number of fragments increases on account of the disappearing metallic phase. The measurements reveal that the metal-insulator transition is a result of the microscopic restructuring that occurs in the system.
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Affiliation(s)
- S Ilani
- Braun Center for Submicron Research, Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel.
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