1
|
Yang X, Ye G, Liu J, Chiechi RC, Koster LJA. Carrier-Carrier Repulsion Limits the Conductivity of N-Doped Organic Semiconductors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024:e2404397. [PMID: 39246234 DOI: 10.1002/adma.202404397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 08/29/2024] [Indexed: 09/10/2024]
Abstract
Molecular doping is a key strategy to enhance the electrical conductivity of organic semiconductors. Typically, the electrical conductivity shows a maximum value upon increased doping, after which the conductivity decreases. This decrease in conductivity is commonly attributed to unfavorable changes in the morphology. However, in recent simulation work, has shown, that the conductivity-at high doping-is instead limited by electron-electron repulsion rather than by morphology, at least for some material combinations. Based on the simulations, this limitation is expected to show up in the dependence of the Seebeck coefficient versus carrier density: the Seebeck coefficient will follow Heike's formula if carrier-carrier repulsion limits the conductivity. Here, the electrical conductivity and Seebeck coefficient are measured as a function of doping for a series of n-type organic semiconductors. Additionally, the resulting carrier density is measured using metal-insulator-semiconductor diodes, which link dopant loading and the number of charge carriers. At high carrier densities, the Seebeck coefficient indeed follows Heike's formula, confirming that the conductivity is limited by carrier-carrier repulsion rather than by morphological effects. This study shows that current models of hopping transport in organic semiconductors may be incomplete. As a result, this study offers novel insights in the design of organic semiconductors.
Collapse
Affiliation(s)
- Xuwen Yang
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 3, Groningen, 9747 AG, The Netherlands
| | - Gang Ye
- Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei Key Laboratory of Polymer Materials, School of Materials Science and Engineering, Hubei University, Youyi Road 368, Wuhan, 430062, P. R. China
| | - Jian Liu
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin, 130022, P. R. China
| | - Ryan C Chiechi
- Department of Chemistry, North Carolina State University, Raleigh, NC, 27695-8204, USA
| | - L Jan Anton Koster
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 3, Groningen, 9747 AG, The Netherlands
| |
Collapse
|
2
|
Gong Z, Lai X, Miao W, Zhong J, Shi Z, Shen H, Liu X, Li Q, Yang M, Zhuang J, Du Y. Br-Vacancies Induced Variable Ranging Hopping Conduction in High-Order Topological Insulator Bi 4Br 4. SMALL METHODS 2024:e2400517. [PMID: 38763921 DOI: 10.1002/smtd.202400517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2024] [Revised: 04/30/2024] [Indexed: 05/21/2024]
Abstract
The defects have a remarkable influence on the electronic structures and the electric transport behaviors of the matter, providing the additional means to engineering their physical properties. In this work, a comprehensive study on the effect of Br-vacancies on the electronic structures and transport behaviors in the high-order topological insulator Bi4Br4 is performed by the combined techniques of the scanning tunneling microscopy (STM), angle-resolved photoemission spectroscopy (ARPES), and physical properties measurement system along with the first-principle calculations. The STM results show the defects on the cleaved surface of a single crystal and reveal that the defects are correlated to the Br-vacancies with the support of the simulated STM images. The role of the Br-vacancies in the modulation of the band structures has been identified by ARPES spectra and the calculated energy-momentum dispersion. The relationship between the Br-vacancies and the semiconducting-like transport behaviors at low temperature has been established, implying a Mott variable ranging hopping conduction in Bi4Br4. The work not only resolves the unclear transport behaviors in this matter, but also paves a way to modulate the electric conduction path by the defects engineering.
Collapse
Affiliation(s)
- Zixin Gong
- School of Physics, Beihang University, Haidian District, Beijing, 100191, China
| | - Xingyu Lai
- School of Physics, Beihang University, Haidian District, Beijing, 100191, China
| | - Wenjing Miao
- School of Physics, Beihang University, Haidian District, Beijing, 100191, China
| | - Jingyuan Zhong
- School of Physics, Beihang University, Haidian District, Beijing, 100191, China
| | - Zhijian Shi
- School of Physics, Beihang University, Haidian District, Beijing, 100191, China
| | - Huayi Shen
- School of Physics, Beihang University, Haidian District, Beijing, 100191, China
| | - Xinqi Liu
- School of Physics, Beihang University, Haidian District, Beijing, 100191, China
| | - Qiyi Li
- School of Physics, Beihang University, Haidian District, Beijing, 100191, China
| | - Ming Yang
- School of Physics, Beihang University, Haidian District, Beijing, 100191, China
| | - Jincheng Zhuang
- School of Physics, Beihang University, Haidian District, Beijing, 100191, China
| | - Yi Du
- School of Physics, Beihang University, Haidian District, Beijing, 100191, China
| |
Collapse
|
3
|
Ihnatsenka S. Model of the Thermoelectric Properties of Anisotropic Organic Semiconductors. ACS PHYSICAL CHEMISTRY AU 2022; 2:118-124. [PMID: 36855510 PMCID: PMC9955154 DOI: 10.1021/acsphyschemau.1c00031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A model of charge hopping transport that accounts for anisotropy of localized states and Coulomb interaction between charges is proposed. For the anisotropic localized states, the degree of orientation relates exponentially to the ratio of conductivities in parallel and perpendicular directions, while the ratio of Seebeck coefficients stays nearly unaffected. However, the ratio of Seebeck coefficients increases if Coulomb interaction is screened stronger in a direction parallel to the predominant orientation of the localized states. This implies two different physical mechanisms responsible for the anisotropy of thermoelectric properties in the hopping regime: electronic state localization for conductivities and screening for Seebeck coefficients. This provides an explanation for the recent experimental findings on tensile drawn and rubbed polymer films.
Collapse
Affiliation(s)
- S. Ihnatsenka
- Department of Science and Technology, Linköping University, SE-60174 Norrköping, Sweden
| |
Collapse
|
4
|
Bansal S, Ali A, Reddy BH, Singh RS. Revelation of Mott insulating state in layered honeycomb lattice Li 2RuO 3. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 34:04LT01. [PMID: 34673565 DOI: 10.1088/1361-648x/ac31fb] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Accepted: 10/21/2021] [Indexed: 06/13/2023]
Abstract
We investigate the role of electron correlation in the electronic structure of honeycomb lattice Li2RuO3using photoemission spectroscopy and band structure calculations. Monoclinic Li2RuO3having Ru network as honeycomb lattice undergoes magneto-structural transition atTc∼ 540 K from high temperature phaseC2/mto low temperature dimerized phaseP21/m. Room temperature valence band photoemission spectra reveal an insulating ground state with no intensity at Fermi level (EF). Ru 4dband extracted from high and low photon energy valence band photoemission spectra reveal that the surface and bulk electronic structures are very similar in this system. Band structure calculations using generalized gradient approximation leads to metallic ground state while screened hybrid (YS-PBE0) functional reveals opening up of a gap in almost degeneratedzx/dyzorbitals, whereasdxyorbital is already gapped. Ru 3dcore level spectra with prominent unscreened feature provides direct evidence of strong electron correlation among Ru 4delectrons which is also manifested by |E-EF|2dependence of spectral density of states in the vicinity ofEFin the high-resolution spectra, establishing Li2RuO3as Mott insulator.
Collapse
Affiliation(s)
- Sakshi Bansal
- Department of Physics, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhauri, Bhopal 462 066, India
| | - Asif Ali
- Department of Physics, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhauri, Bhopal 462 066, India
| | - B H Reddy
- Department of Physics, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhauri, Bhopal 462 066, India
| | - Ravi Shankar Singh
- Department of Physics, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhauri, Bhopal 462 066, India
| |
Collapse
|
5
|
Pedramrazi Z, Herbig C, Pulkin A, Tang S, Phillips M, Wong D, Ryu H, Pizzochero M, Chen Y, Wang F, Mele EJ, Shen ZX, Mo SK, Yazyev OV, Crommie MF. Manipulating Topological Domain Boundaries in the Single-Layer Quantum Spin Hall Insulator 1T'-WSe 2. NANO LETTERS 2019; 19:5634-5639. [PMID: 31329449 DOI: 10.1021/acs.nanolett.9b02157] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We report the creation and manipulation of structural phase boundaries in the single-layer quantum spin Hall insulator 1T'-WSe2 by means of scanning tunneling microscope tip pulses. We observe the formation of one-dimensional interfaces between topologically nontrivial 1T' domains having different rotational orientations, as well as induced interfaces between topologically nontrivial 1T' and topologically trivial 1H phases. Scanning tunneling spectroscopy measurements show that 1T'/1T' interface states are localized at domain boundaries, consistent with theoretically predicted unprotected interface modes that form dispersive bands in and around the energy gap of this quantum spin Hall insulator. We observe a qualitative difference in the experimental spectral line shape between topologically "unprotected" states at 1T'/1T' domain boundaries and protected states at 1T'/1H and 1T'/vacuum boundaries in single-layer WSe2.
Collapse
Affiliation(s)
- Zahra Pedramrazi
- Department of Physics , University of California at Berkeley , Berkeley , California 94720 , United States
| | - Charlotte Herbig
- Department of Physics , University of California at Berkeley , Berkeley , California 94720 , United States
| | - Artem Pulkin
- Institute of Physics , Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland
- Division of Chemistry and Chemical Engineering , California Institute of Technology , Pasadena , California 91125 , United States
| | - Shujie Tang
- Advanced Light Source , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
- Stanford Institute for Materials and Energy Sciences , SLAC National Accelerator Laboratory , Menlo Park , California 94025 , United States
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics , Stanford University , Stanford , California 94305 , United States
| | - Madeleine Phillips
- Department of Physics and Astronomy , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
- Center for Computational Materials Science , Naval Research Laboratory , Washington , D.C. 20375 , United States
| | - Dillon Wong
- Department of Physics , University of California at Berkeley , Berkeley , California 94720 , United States
| | - Hyejin Ryu
- Advanced Light Source , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
- Center for Spintronics , Korea Institute of Science and Technology , Seoul 02792 , Korea
| | - Michele Pizzochero
- Institute of Physics , Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland
| | - Yi Chen
- Department of Physics , University of California at Berkeley , Berkeley , California 94720 , United States
| | - Feng Wang
- Department of Physics , University of California at Berkeley , Berkeley , California 94720 , United States
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
- Kavli Energy NanoScience Institute at the University of California Berkeley and the Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Eugene J Mele
- Department of Physics and Astronomy , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Zhi-Xun Shen
- Stanford Institute for Materials and Energy Sciences , SLAC National Accelerator Laboratory , Menlo Park , California 94025 , United States
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics , Stanford University , Stanford , California 94305 , United States
| | - Sung-Kwan Mo
- Advanced Light Source , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Oleg V Yazyev
- Institute of Physics , Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland
- National Centre for Computational Design and Discovery of Novel Materials MARVEL , Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland
| | - Michael F Crommie
- Department of Physics , University of California at Berkeley , Berkeley , California 94720 , United States
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
- Kavli Energy NanoScience Institute at the University of California Berkeley and the Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| |
Collapse
|
6
|
Pollak M. On dynamical properties of electrons in Anderson-Mott insulators. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:105602. [PMID: 29393067 DOI: 10.1088/1361-648x/aaac94] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Properties of electrons in non-crystalline (alias disordered) systems has been a very active research topic for over half a century, since Anderson's ground breaking paper on localization. In strongly disordered systems electrons become Anderson and Mott localized. Interactions become important because screening by localized electrons is ineffective. Dynamical theories for such systems have long been controversial. Nevertheless one theory came to prominence in the literature and is often invoked and/or used. It is shown here that that theory is unsatisfactory in several aspects. It is based on the one-particle density of states, which turns out to be irrelevant to the problem it addresses. Another shortcoming is an implicit conjecture that interacting electrons move independently of each other. The theory is also in questionable agreement with experiment. It is shown that two other theories are free of those problems. They are useful for different types of studies, are compatible with each other and in agreement with experiment.
Collapse
Affiliation(s)
- M Pollak
- Department of Physics, University of California, Riverside, CA 93405, United States of America
| |
Collapse
|
7
|
Abstract
Monolayer graphene exhibits many spectacular electronic properties, with superconductivity being arguably the most notable exception. It was theoretically proposed that superconductivity might be induced by enhancing the electron-phonon coupling through the decoration of graphene with an alkali adatom superlattice [Profeta G, Calandra M, Mauri F (2012) Nat Phys 8(2):131-134]. Although experiments have shown an adatom-induced enhancement of the electron-phonon coupling, superconductivity has never been observed. Using angle-resolved photoemission spectroscopy (ARPES), we show that lithium deposited on graphene at low temperature strongly modifies the phonon density of states, leading to an enhancement of the electron-phonon coupling of up to λ ≃ 0.58. On part of the graphene-derived π*-band Fermi surface, we then observe the opening of a Δ ≃ 0.9-meV temperature-dependent pairing gap. This result suggests for the first time, to our knowledge, that Li-decorated monolayer graphene is indeed superconducting, with Tc ≃ 5.9 K.
Collapse
|
8
|
Shimer MT, Täuber UC, Pleimling M. Nonequilibrium relaxation and aging scaling of the Coulomb and Bose glass. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 90:032111. [PMID: 25314399 DOI: 10.1103/physreve.90.032111] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Indexed: 06/04/2023]
Abstract
We employ Monte Carlo simulations to investigate the nonequilibrium relaxation properties of the two- and three-dimensional Coulomb glass with different long-range repulsive interactions. Specifically, we explore the aging scaling laws in the two-time density autocorrelation function. We find that, in the time window and parameter range accessible to us, the scaling exponents are not universal, depending on the filling fraction and temperature: As either the temperature decreases or the filling fraction deviates more from half filling, the exponents reflect markedly slower relaxation kinetics. In comparison with a repulsive Coulomb potential, appropriate for impurity states in strongly disordered semiconductors, we observe that, for logarithmic interactions, the soft pseudogap in the density of states is considerably broader, and the dependence of the scaling exponents on external parameters is much weaker. The latter situation is relevant for flux creep in the disorder-dominated Bose glass phase of type-II superconductors subject to columnar pinning centers.
Collapse
Affiliation(s)
- Matthew T Shimer
- Department of Physics (MC 0435), Robeson Hall, 850 West Campus Drive, Virginia Tech, Blacksburg, Virginia 24061, USA and hMetrix LLC, 150 Monument Rd, # 107, Bala Cynwyd, Pennsylvania 19004, USA
| | - Uwe C Täuber
- Department of Physics (MC 0435), Robeson Hall, 850 West Campus Drive, Virginia Tech, Blacksburg, Virginia 24061, USA
| | - Michel Pleimling
- Department of Physics (MC 0435), Robeson Hall, 850 West Campus Drive, Virginia Tech, Blacksburg, Virginia 24061, USA
| |
Collapse
|
9
|
Complex spectral evolution in a BCS superconductor, ZrB12. Sci Rep 2013; 3:3342. [PMID: 24275904 PMCID: PMC3840362 DOI: 10.1038/srep03342] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Accepted: 11/12/2013] [Indexed: 11/28/2022] Open
Abstract
We investigate the electronic structure of a complex conventional superconductor, ZrB12 employing high resolution photoemission spectroscopy and ab initio band structure calculations. The experimental valence band spectra could be described reasonably well within the local density approximation. Energy bands close to the Fermi level possess t2g symmetry and the Fermi level is found to be in the proximity of quantum fluctuation regime. The spectral lineshape in the high resolution spectra is complex exhibiting signature of a deviation from Fermi liquid behavior. A dip at the Fermi level emerges above the superconducting transition temperature that gradually grows with the decrease in temperature. The spectral simulation of the dip and spectral lineshape based on a phenomenological self energy suggests finite electron pair lifetime and a pseudogap above the superconducting transition temperature.
Collapse
|
10
|
Chen T, Skinner B, Shklovskii BI. Coulomb gap triptych in a periodic array of metal nanocrystals. PHYSICAL REVIEW LETTERS 2012; 109:126805. [PMID: 23005975 DOI: 10.1103/physrevlett.109.126805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Indexed: 06/01/2023]
Abstract
The Coulomb gap in the single-particle density of states (DOS) is a universal consequence of electron-electron interaction in disordered systems with localized electron states. Here we show that in arrays of monodisperse metallic nanocrystals, there is not one but three identical adjacent Coulomb gaps, which together form a structure that we call a "Coulomb gap triptych." We calculate the DOS and the conductivity in two- and three-dimensional arrays using a computer simulation. Unlike in the conventional Coulomb glass models, in nanocrystal arrays the DOS has a fixed width in the limit of large disorder. The Coulomb gap triptych can be studied via tunneling experiments.
Collapse
Affiliation(s)
- Tianran Chen
- Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, 55455, USA
| | | | | |
Collapse
|
11
|
Mott-Anderson Transition in Molecular Conductors: Influence of Randomness on Strongly Correlated Electrons in the κ-(BEDT-TTF)2X System. CRYSTALS 2012. [DOI: 10.3390/cryst2020374] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
12
|
Qin S, Kim TH, Zhang Y, Ouyang W, Weitering HH, Shih CK, Baddorf AP, Wu R, Li AP. Correlating electronic transport to atomic structures in self-assembled quantum wires. NANO LETTERS 2012; 12:938-942. [PMID: 22268695 DOI: 10.1021/nl204003s] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Quantum wires, as a smallest electronic conductor, are expected to be a fundamental component in all quantum architectures. The electronic conductance in quantum wires, however, is often dictated by structural instabilities and electron localization at the atomic scale. Here we report on the evolutions of electronic transport as a function of temperature and interwire coupling as the quantum wires of GdSi(2) are self-assembled on Si(100) wire-by-wire. The correlation between structure, electronic properties, and electronic transport are examined by combining nanotransport measurements, scanning tunneling microscopy, and density functional theory calculations. A metal-insulator transition is revealed in isolated nanowires, while a robust metallic state is obtained in wire bundles at low temperature. The atomic defects lead to electron localizations in isolated nanowire, and interwire coupling stabilizes the structure and promotes the metallic states in wire bundles. This illustrates how the conductance nature of a one-dimensional system can be dramatically modified by the environmental change on the atomic scale.
Collapse
Affiliation(s)
- Shengyong Qin
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Long YZ, Duvail JL, Chen ZJ, Jin AZ, Gu CZ. Electrical properties of isolated poly(3,4-ethylenedioxythiophene) nanowires prepared by template synthesis. POLYM ADVAN TECHNOL 2009. [DOI: 10.1002/pat.1379] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
14
|
Surer B, Katzgraber HG, Zimanyi GT, Allgood BA, Blatter G. Density of states and critical behavior of the Coulomb glass. PHYSICAL REVIEW LETTERS 2009; 102:067205. [PMID: 19257630 DOI: 10.1103/physrevlett.102.067205] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2008] [Revised: 09/10/2008] [Indexed: 05/27/2023]
Abstract
We present zero-temperature simulations for the single-particle density of states of the Coulomb glass. Our results in three dimensions are consistent with the Efros and Shklovskii prediction for the density of states. Finite-temperature Monte Carlo simulations show no sign of a thermodynamic glass transition down to low temperatures, in disagreement with mean-field theory. Furthermore, the random-displacement formulation of the model undergoes a transition into a distorted Wigner crystal for a surprisingly broad range of the disorder strength.
Collapse
Affiliation(s)
- Brigitte Surer
- Theoretische Physik, ETH Zurich, CH-8093 Zurich, Switzerland
| | | | | | | | | |
Collapse
|
15
|
Affiliation(s)
- Amir Zabet-Khosousi
- Lash Miller Chemical Laboratories, University of Toronto, Ontario M5S 3H6, Canada
| | - Al-Amin Dhirani
- Lash Miller Chemical Laboratories, University of Toronto, Ontario M5S 3H6, Canada
| |
Collapse
|
16
|
Somoza AM, Ortuño M, Caravaca M, Pollak M. Effective temperature in relaxation of Coulomb glasses. PHYSICAL REVIEW LETTERS 2008; 101:056601. [PMID: 18764413 DOI: 10.1103/physrevlett.101.056601] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2008] [Indexed: 05/26/2023]
Abstract
We study relaxation in two-dimensional Coulomb glasses up to macroscopic times. We use a kinetic Monte Carlo algorithm especially designed to escape efficiently from deep valleys around metastable states. We find that, during the relaxation process, the site occupancy follows a Fermi-Dirac distribution with an effective temperature much higher than the real temperature T. Long electron-hole excitations are characterized by T(eff), while short ones are thermalized at T. We argue that the density of states at the Fermi level is proportional to T(eff) and is a good thermometer to measure it. T(eff) decreases extremely slowly, roughly as the inverse of the logarithm of time, and it should affect hopping conductance in many experimental circumstances.
Collapse
Affiliation(s)
- A M Somoza
- Departamento de Física-CIOyN, Universidad de Murcia, Murcia, Spain
| | | | | | | |
Collapse
|
17
|
Long YZ, Yin ZH, Chen ZJ, Jin AZ, Gu CZ, Zhang HT, Chen XH. Low-temperature electronic transport in single K(0.27)MnO(2)·0.5H(2)O nanowires: enhanced electron-electron interaction. NANOTECHNOLOGY 2008; 19:215708. [PMID: 21730587 DOI: 10.1088/0957-4484/19/21/215708] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The current-voltage (I-V) characteristics and electrical resistivity of isolated potassium manganese oxide (K(0.27)MnO(2)·0.5H(2)O) nanowires prepared by a simple hydrothermal method were investigated over a wide temperature range from 300 to 4 K. With lowering temperature, a transition from linear to nonlinear I-V curves was observed around 50 K, and a clear zero bias anomaly (i.e., Coulomb gap-like structure) appeared on the differential conductance (dI/dV) curves, possibly due to enhanced electron-electron interaction at low temperatures. The temperature dependence of resistivity, [Formula: see text], follows the Efros-Shklovskii (ES) law, as expected in the presence of a Coulomb gap. Here we note that both the ES law and Coulomb blockade can in principle lead to a reduced zero bias conductance at low temperatures; in this study we cannot exclude the possibility of Coulomb-blockade transport in the measured nanowires, especially in the low-temperature range. It is still an open question how to pin down the origin of the observed reduction to a Coulomb gap (ES law) or Coulomb blockade.
Collapse
Affiliation(s)
- Y Z Long
- College of Physics Science, Qingdao University, Qingdao 266071, People's Republic of China
| | | | | | | | | | | | | |
Collapse
|
18
|
Kobayashi M, Tanaka K, Fujimori A, Ray S, Sarma DD. Critical test for Altshuler-Aronov theory: evolution of the density of states singularity in double perovskite Sr2FeMoO6 with controlled disorder. PHYSICAL REVIEW LETTERS 2007; 98:246401. [PMID: 17677976 DOI: 10.1103/physrevlett.98.246401] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2007] [Indexed: 05/16/2023]
Abstract
With high-resolution photoemission spectroscopy measurements, the density of states (DOS) near the Fermi level (E(F)) of double perovskite Sr(2)FeMoO(6) having different degrees of Fe/Mo antisite disorder has been investigated with varying temperature. The DOS near E(F) showed a systematic depletion with increasing degree of disorder, and recovered with increasing temperature. Altshuler-Aronov (AA) theory of disordered metals well explains the dependences of the experimental results. Scaling analysis of the spectra provides experimental indication for the functional form of the AA DOS singularity.
Collapse
Affiliation(s)
- M Kobayashi
- Department of Physics, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan
| | | | | | | | | |
Collapse
|
19
|
Pappert K, Schmidt MJ, Hümpfner S, Rüster C, Schott GM, Brunner K, Gould C, Schmidt G, Molenkamp LW. Magnetization-switched metal-insulator transition in a (Ga,Mn)as tunnel device. PHYSICAL REVIEW LETTERS 2006; 97:186402. [PMID: 17155562 DOI: 10.1103/physrevlett.97.186402] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2006] [Indexed: 05/12/2023]
Abstract
We observe the occurrence of an Efros-Shklovskii gap in (Ga,Mn)As based tunnel junctions. The occurrence of the gap is controlled by the extent of the hole wave function on the Mn acceptor atoms. Using k.p-type calculations we show that this extent depends crucially on the direction of the magnetization in the (Ga,Mn)As (which has two almost equivalent easy axes). This implies one can reversibly tune the system into the insulating or metallic state by changing the magnetization.
Collapse
Affiliation(s)
- K Pappert
- Physikalisches Institut (EP3), Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Chapter 6 Electron Transport. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/s1572-0934(06)02006-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023]
|
21
|
Maiti K, Singh RS, Medicherla VRR, Rayaprol S, Sampathkumaran EV. Origin of charge density wave formation in insulators from a high resolution photoemission study of BaIrO3. PHYSICAL REVIEW LETTERS 2005; 95:016404. [PMID: 16090637 DOI: 10.1103/physrevlett.95.016404] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2005] [Indexed: 05/03/2023]
Abstract
We investigate the origin of charge density wave (CDW) formation in insulators by studying BaIrO3 using high-resolution (1.4 meV) photoemission spectroscopy. The spectra reveal the existence of localized density of states at the Fermi level, E(F), in the vicinity of room temperature. These localized states are found to vanish as the temperature is lowered, thereby, opening a soft gap at E(F), as a consequence of CDW transition. In addition, the energy dependence of the spectral density of states reveals the importance of magnetic interactions, rather than well-known Coulomb repulsion effect, in determining the electronic structure thereby implying a close relationship between ferromagnetism and CDW observed in this compound. Also, Ba core level spectra surprisingly exhibit an unusual behavior prior to CDW transition.
Collapse
Affiliation(s)
- Kalobaran Maiti
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai-400 005, India
| | | | | | | | | |
Collapse
|
22
|
Müller M, Ioffe LB. Glass transition and the Coulomb gap in electron glasses. PHYSICAL REVIEW LETTERS 2004; 93:256403. [PMID: 15697920 DOI: 10.1103/physrevlett.93.256403] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2004] [Indexed: 05/24/2023]
Abstract
We establish the connection between the presence of a glass phase and the appearance of a Coulomb gap in disordered materials with strongly interacting electrons. Treating multiparticle correlations in a systematic way, we show that in the case of strong disorder a continuous glass transition takes place whose Landau expansion is identical to that of the Sherrington-Kirkpatrick spin glass. We show that the marginal stability of the glass phase controls the physics of these systems: it results in slow dynamics and leads to the formation of a Coulomb gap.
Collapse
Affiliation(s)
- M Müller
- Department of Physics, Rutgers University, Piscataway, New Jersey 08854, USA
| | | |
Collapse
|
23
|
Lee M. Phase diagram of coulomb interactions across the metal-insulator transition in Si:B. PHYSICAL REVIEW LETTERS 2004; 93:256401. [PMID: 15697918 DOI: 10.1103/physrevlett.93.256401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2004] [Indexed: 05/24/2023]
Abstract
Measurements of the single-particle density of states (DOS) near T=0 K in Si:B are used to construct an energy-density phase diagram of Coulomb interactions across the critical density n(c) of the metal-insulator transition. Insulators and metals are found to be distinguishable only below a phase boundary epsilon*(|n/n(c)-1|) determined by the Coulomb energy. Above epsilon* is a mixed state where metals and insulators equidistant from n(c) cannot be distinguished from their DOS structure. The data imply a diverging screening radius at n(c), which may signal an interaction-driven thermodynamic state change.
Collapse
Affiliation(s)
- Mark Lee
- Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185-1415, USA.
| |
Collapse
|
24
|
Sandow B, Bleibaum O, Schirmacher W. Tunneling spectroscopy in the hopping regime. ACTA ACUST UNITED AC 2003. [DOI: 10.1002/pssc.200303639] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- B. Sandow
- Institut für Experimentalphysik, Freie Universität Berlin, 14195 Berlin, Germany
| | - O. Bleibaum
- Institut für Theoretische Physik, Otto‐von‐Guericke Universität Magdeburg, 39016 Magdeburg, PF 4120, Germany
| | - W. Schirmacher
- Physik‐Department E13, Technische Universität München, James‐Franck‐Straße 1, 85747 Garching, Germany
| |
Collapse
|
25
|
Kozub VI. Comment on "Electronic correlation effects and the Coulomb gap at finite temperature". PHYSICAL REVIEW LETTERS 2002; 89:229701-229702. [PMID: 12485111 DOI: 10.1103/physrevlett.89.229701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2002] [Indexed: 05/24/2023]
|
26
|
Lee M, Stutzmann ML. Microwave ac conductivity spectrum of a Coulomb glass. PHYSICAL REVIEW LETTERS 2001; 87:056402. [PMID: 11497794 DOI: 10.1103/physrevlett.87.056402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2000] [Indexed: 05/23/2023]
Abstract
We report the first observation of the transition between interacting and noninteracting behavior in the ac conductivity spectrum sigma(omega) of a doped semiconductor in its Coulomb glass state near T = 0 K. The transition manifests itself as a crossover from approximately linear frequency dependence below approximately 10 GHz, to quadratic dependence above approximately 15 GHz. The sharpness of the transition and the magnitude of the crossover frequency strongly suggest that the transition is driven by photon-induced excitations across the Coulomb gap, in contrast to existing theoretical descriptions.
Collapse
Affiliation(s)
- M Lee
- Bell Laboratories-Lucent Technologies, 600 Mountain Avenue, Murray Hill, New Jersey 07974, USA.
| | | |
Collapse
|
27
|
Bielejec E, Ruan J, Wu W. Hard correlation gap observed in quench-condensed ultrathin beryllium. PHYSICAL REVIEW LETTERS 2001; 87:036801. [PMID: 11461578 DOI: 10.1103/physrevlett.87.036801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2000] [Indexed: 05/23/2023]
Abstract
We report on the tunneling density of states (DOS) in strongly disordered ultrathin Be films quench condensed at 20 K. Above 5 K, the DOS shows the well-known logarithmic anomaly at the Fermi level. Only in a narrow temperature range near 2 K is the DOS linearly dependent on energy, as predicted by Efros and Shklovskii. However, both the zero-bias conductance and the slope of the linear DOS are found to decrease drastically with decreasing temperature. Tunneling measurements at mK temperatures have revealed conclusively that a hard correlation gap opens up in the DOS.
Collapse
Affiliation(s)
- E Bielejec
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
| | | | | |
Collapse
|
28
|
Sandow B, Gloos K, Rentzsch R, Ionov AN, Schirmacher W. Electronic correlation effects and the Coulomb gap at finite temperature. PHYSICAL REVIEW LETTERS 2001; 86:1845-1848. [PMID: 11290263 DOI: 10.1103/physrevlett.86.1845] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2000] [Indexed: 05/23/2023]
Abstract
We have investigated the effect of the long-range Coulomb interaction on the one-particle excitation spectrum of n-type germanium, using tunneling spectroscopy on mechanically controllable break junctions. At low temperatures, the tunnel conductance shows a minimum at zero bias voltage due to the Coulomb gap. Above 1 K, the gap is filled by thermal excitations. This behavior is reflected in the variable-range hopping resistivity measured on the same samples: up to a few degrees Kelvin the Efros-Shklovskii lnR infinity T(-1/2) law is obeyed, whereas at higher temperatures deviations from this law occur. The type of crossover differs from that considered previously in the literature.
Collapse
Affiliation(s)
- B Sandow
- Institut für Experimentalphysik, Freie Universität Berlin, Germany
| | | | | | | | | |
Collapse
|
29
|
Teizer W, Hellman F, Dynes RC. Density of states of amorphous GdxSi1-x at the metal-insulator transition. PHYSICAL REVIEW LETTERS 2000; 85:848-851. [PMID: 10991414 DOI: 10.1103/physrevlett.85.848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2000] [Indexed: 05/23/2023]
Abstract
We have determined the electronic density of states of amorphous Gd xSi (1-x), N(GdSi)(E), in the vicinity of the metal-insulator transition by measuring the tunneling conductance dI/dV across a Gd xSi (1-x)/oxide/Pb tunnel junction at low T (T approximately 100 mK). By applying a magnetic field we can tune through the metal-insulator transition and simultaneously measure the transport and N(E) on a single sample. We find a smooth transition from a metal with strong Coulomb interactions to a developing Coulomb gap in the insulating regime. In the metallic region N(GdSi)(0) scales approximately with sigma(2).
Collapse
Affiliation(s)
- W Teizer
- Department of Physics, University of California, San Diego, La Jolla, California 92093, USA
| | | | | |
Collapse
|
30
|
Butko VY, DiTusa JF, Adams PW. Tenfold magnetoconductance in a nonmagnetic metal film. PHYSICAL REVIEW LETTERS 2000; 85:162-165. [PMID: 10991184 DOI: 10.1103/physrevlett.85.162] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/1999] [Indexed: 05/23/2023]
Abstract
We present magnetoconductance (MC) measurements of homogeneously disordered Be films whose zero field sheet conductance ( G) is described by the Efros-Shklovskii hopping law G(T) = (2e(2)/h)exp-(T0/T)(1/2). The low field MC of the films is negative with G decreasing a factor of 2 below 1 T. In contrast the MC above 1 T is strongly positive. At 8 T, G increases tenfold in perpendicular field and fivefold in parallel field. In the simpler parallel case, we observe field enhanced variable range hopping characterized by an attenuation of T0 via the Zeeman interaction.
Collapse
Affiliation(s)
- VY Butko
- Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70806, USA
| | | | | |
Collapse
|
31
|
Butko VY, DiTusa JF, Adams PW. Coulomb gap: how a metal film becomes an insulator. PHYSICAL REVIEW LETTERS 2000; 84:1543-1546. [PMID: 11017563 DOI: 10.1103/physrevlett.84.1543] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/1999] [Indexed: 05/23/2023]
Abstract
Electron tunneling measurements of the density of states (DOS) in ultrathin Be films reveal that a correlation gap mediates their insulating behavior. In films with sheet resistance R<5000 Omega the correlation singularity appears as the usual perturbative ln(V) zero bias anomaly (ZBA) in the DOS. As R is increased further, however, the ZBA grows and begins to dominate the DOS spectrum. This evolution continues until a nonperturbative |V| Efros-Shklovskii Coulomb gap spectrum finally emerges in the highest R films. Transport measurements of films which display this gap are well described by a universal variable range hopping law R(T) = (h/2e(2))exp(T0/T)(1/2).
Collapse
Affiliation(s)
- VY Butko
- Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70806, USA
| | | | | |
Collapse
|
32
|
Meir Y. Universal Crossover between Efros-Shklovskii and Mott Variable-Range-Hopping Regimes. PHYSICAL REVIEW LETTERS 1996; 77:5265-5267. [PMID: 10062757 DOI: 10.1103/physrevlett.77.5265] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
|
33
|
Massey JG, Lee M. Electron Tunneling Study of Coulomb Correlations across the Metal-Insulator Transition in Si:B. PHYSICAL REVIEW LETTERS 1996; 77:3399-3402. [PMID: 10062210 DOI: 10.1103/physrevlett.77.3399] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
|