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Iron phthalocyanine on Au(111) is a "non-Landau" Fermi liquid. Nat Commun 2021; 12:6027. [PMID: 34654828 PMCID: PMC8521586 DOI: 10.1038/s41467-021-26339-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 09/28/2021] [Indexed: 11/24/2022] Open
Abstract
The paradigm of Landau’s Fermi liquid theory has been challenged with the finding of a strongly interacting Fermi liquid that cannot be adiabatically connected to a non-interacting system. A spin-1 two-channel Kondo impurity with anisotropy D has a quantum phase transition between two topologically different Fermi liquids with a peak (dip) in the Fermi level for D < Dc (D > Dc). Extending this theory to general multi-orbital problems with finite magnetic field, we reinterpret in a unified and consistent fashion several experimental studies of iron phthalocyanine molecules on Au(111) that were previously described in disconnected and conflicting ways. The differential conductance shows a zero-bias dip that widens when the molecule is lifted from the surface (reducing the Kondo couplings) and is transformed continuously into a peak under an applied magnetic field. We reproduce all features and propose an experiment to induce the topological transition. Single molecules on metal surfaces are paradigmatic systems for the study of many-body phenomena. Here, the authors show that several spectroscopic experiments on iron phthalocyanine on Au(111) surface can be described in a unified way in terms of a strongly interacting topologically non-trivial (non-Landau) Fermi liquid.
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2
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Theory of Differential Conductance of Co on Cu(111) Including Co s and d Orbitals, and Surface and Bulk Cu States. PHYSICAL REVIEW LETTERS 2021; 126:046801. [PMID: 33576682 DOI: 10.1103/physrevlett.126.046801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 01/07/2021] [Indexed: 06/12/2023]
Abstract
We revisit the theory of the Kondo effect observed by a scanning-tunneling microscope (STM) for transition-metal atoms (TMAs) on noble-metal surfaces, including d and s orbitals of the TMA, surface and bulk conduction states of the metal, and their hopping to the tip of the STM. Fitting the experimentally observed STM differential conductance for Co on Cu(111) including both the Kondo feature near the Fermi energy and the resonance below the surface band, we conclude that the STM senses mainly the Co s orbital and that the Kondo antiresonance is due to interference between states with electrons in the s orbital and a localized d orbital mediated by the conduction states.
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Tomography of Zero-Energy End Modes in Topological Superconducting Wires. PHYSICAL REVIEW LETTERS 2020; 125:256801. [PMID: 33416361 DOI: 10.1103/physrevlett.125.256801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 11/19/2020] [Indexed: 06/12/2023]
Abstract
We describe the Majorana zero modes in topological hybrid superconductor-semiconductor wires with spin-orbit coupling and magnetic field, in terms of generalized Bloch coordinates φ,θ,δ. When the spin-orbit coupling and the magnetic field are perpendicular, φ and δ are universal in an appropriate coordinate system. We show how to extract the angle θ from the behavior of the Josephson current-phase relation, which enables tomography of the Majorana modes. Simple analytical expressions describe accurately the numerical results.
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4
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Destructive quantum interference in transport through molecules with electron-electron and electron-vibration interactions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:465602. [PMID: 31357183 DOI: 10.1088/1361-648x/ab3684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We study the transport through a molecular junction exhibiting interference effects. We show that these effects can still be observed in the presence of molecular vibrations if Coulomb repulsion is taken into account. In the Kondo regime, the conductance of the junction can be changed by several orders of magnitude by tuning the levels of the molecule, or displacing a contact between two atoms, from nearly perfect destructive interference to values of the order of 2e 2/h expected in Kondo systems. We also show that this large conductance change is robust for reasonable temperatures and voltages for symmetric and asymmetric tunnel couplings between the source-drain electrodes and the molecular orbitals. This is relevant for the development of quantum interference effect transistors based on molecular junctions.
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Ginzburg-Landau theory for the magnetic and structural transitions in La 1-y (Ca 1-x Sr x ) y MnO 3. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:025804. [PMID: 30521486 DOI: 10.1088/1361-648x/aaef56] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We present a phenomenological theory for the ferromagnetic transition temperature, the magnetic susceptibility at high temperatures, and the structural distortion in the La[Formula: see text](Ca[Formula: see text]Sr[Formula: see text])[Formula: see text]MnO[Formula: see text] system. We construct a Ginzburg-Landau free energy that describes the magnetic and the structural transitions, and a competition between them. The parameters of the magnetic part of the free energy are derived from a mean-field solution of the magnetic interaction for arbitrary angular momentum. The theory provides a qualitative description of the observed magnetic and structural phase transitions as functions of Sr-doping level ([Formula: see text]) for [Formula: see text].
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Two-stage three-channel Kondo physics for an FePc molecule on the Au(1 1 1) surface. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:374003. [PMID: 30095081 DOI: 10.1088/1361-648x/aad973] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We study an impurity Anderson model to describe an iron phthalocyanine (FePc) molecule on Au(1 1 1), motivated by previous results of scanning tunneling spectroscopy (STS) and theoretical studies. The model hybridizes a spin doublet consisting in one hole at the [Formula: see text] orbital of iron and two degenerate doublets corresponding to one hole either in the 3d xz or in the 3d yz orbital (called π orbitals) with two degenerate Hund-rule triplets with one hole in the 3d z orbital and another one in a π orbital. We solve the model using a slave-boson mean-field approximation (SBMFA). For reasonable parameters we can describe very well the observed STS spectrum between sample bias -60 mV to 20 mV. For these parameters the Kondo effect takes place in two stages, with different energy scales [Formula: see text] corresponding to the Kondo temperatures related with the hopping of the z 2 and π orbitals respectively. There is a strong interference between the different channels and the Kondo temperatures, particularly the lowest one is strongly reduced compared with the value in the absence of the competing channel.
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Generalized One-Band Model Based on Zhang-Rice Singlets for Tetragonal CuO. PHYSICAL REVIEW LETTERS 2018; 120:177001. [PMID: 29756839 DOI: 10.1103/physrevlett.120.177001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Indexed: 06/08/2023]
Abstract
Tetragonal CuO (T-CuO) has attracted attention because of its structure similar to that of the cuprates. It has been recently proposed as a compound whose study can give an end to the long debate about the proper microscopic modeling for cuprates. In this work, we rigorously derive an effective one-band generalized t-J model for T-CuO, based on orthogonalized Zhang-Rice singlets, and make an estimative calculation of its parameters, based on previous ab initio calculations. By means of the self-consistent Born approximation, we then evaluate the spectral function and the quasiparticle dispersion for a single hole doped in antiferromagnetically ordered half filled T-CuO. Our predictions show very good agreement with angle-resolved photoemission spectra and with theoretical multiband results. We conclude that a generalized t-J model remains the minimal Hamiltonian for a correct description of single-hole dynamics in cuprates.
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Leading temperature dependence of the conductance in Kondo-correlated quantum dots. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:155304. [PMID: 29508772 DOI: 10.1088/1361-648x/aab45b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Using renormalized perturbation theory in the Coulomb repulsion, we derive an analytical expression for the leading term in the temperature dependence of the conductance through a quantum dot described by the impurity Anderson model, in terms of the renormalized parameters of the model. Taking these parameters from the literature, we compare the results with published ones calculated using the numerical renormalization group obtaining a very good agreement. The approach is superior to alternative perturbative treatments. We compare in particular to the results of a simple interpolative perturbation approach.
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9
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Kondo behavior and conductance through 3d impurities in gold chains doped with oxygen. J Chem Phys 2017. [DOI: 10.1063/1.4973982] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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10
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Restoring the SU(4) Kondo regime in a double quantum dot system. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:335601. [PMID: 26235364 DOI: 10.1088/0953-8984/27/33/335601] [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
We calculate the spectral density and occupations of a system of two capacitively coupled quantum dots, each one connected to its own pair of conducting leads, in a regime of parameters in which the total couplings to the leads for each dot Γ(i) are different. The system has been used recently to perform pseudospin spectroscopy by controlling independently the voltages of the four leads. For an odd number of electrons in the system, equal coupling to the leads Γ1 = Γ2, equal dot levels E1 = E2 and sufficiently large interdot repulsion U12 the system lies in the SU(4) symmetric point of spin and pseudospin degeneracy in the Kondo regime. In the more realistic case Γ1 ≠ Γ2, pseudospin degeneracy is broken and the symmetry is reduced to SU(2). Nevertheless, we find that the essential features of the SU(4) symmetric case are recovered by appropriately tuning the level difference δ = E2 - E1. After this tuning, the system behaves as an SU(4) Kondo one at low energies. Our results are relevant for experiments which look for signatures of SU(4) symmetry in the Kondo regime of similar systems.
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Interpretation of experimental results on Kondo systems with crystal field. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:025602. [PMID: 24326384 DOI: 10.1088/0953-8984/26/2/025602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We present a simple approach to calculate the thermodynamic properties of single Kondo impurities including orbital degeneracy and crystal field effects (CFE) by extending a previous proposal by Schotte and Schotte (1975 Phys. Lett. 55A 38). Comparison with exact solutions for the specific heat of a quartet ground state split into two doublets shows deviations below 10% in the absence of CFE and a quantitative agreement for moderate or large CFE. As an application, we fit the measured specific heat of the compounds CeCu2Ge2, CePd3Si0.3, CePdAl, CePt, Yb2Pd2Sn and YbCo2Zn20. The agreement between theory and experiment is very good or excellent depending on the compound, except at very low temperatures due to the presence of magnetic correlations (not accounted for in the model).
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12
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Comment on "Universal out-of-equilibrium transport in Kondo-correlated quantum dots: renormalized dual fermions on the Keldysh contour". PHYSICAL REVIEW LETTERS 2013; 111:089701. [PMID: 24010483 DOI: 10.1103/physrevlett.111.089701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Indexed: 06/02/2023]
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13
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Non-Fermi-liquid behavior in transport through Co-doped Au chains. PHYSICAL REVIEW LETTERS 2013; 110:196402. [PMID: 23705724 DOI: 10.1103/physrevlett.110.196402] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Indexed: 06/02/2023]
Abstract
We calculate the conductance as a function of temperature G(T) through Au monatomic chains containing one Co atom as a magnetic impurity, and connected to two conducting leads with a fourfold symmetry axis. Using the information derived from ab initio calculations, we construct an effective model Ĥ(eff) that hybridizes a 3d(7) quadruplet at the Co site with two 3d(8) triplets through the hopping of 5d(xz) and 5d(yz) electrons of Au. The quadruplet is split by spin anisotropy due to spin-orbit coupling. Solving Ĥ(eff) with the numerical renormalization group we find that at low temperatures G(T)=a-b√[T] and the ground state impurity entropy is ln(2)/2, a behavior similar to the two-channel Kondo model. Stretching the chain leads to a non-Kondo phase, with the physics of the underscreened Kondo model at the quantum critical point.
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Non-equilibrium conductance through a benzene molecule in the Kondo regime. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:365301. [PMID: 22892707 DOI: 10.1088/0953-8984/24/36/365301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Starting from exact eigenstates for a symmetric ring, we derive a low-energy effective generalized Anderson Hamiltonian which contains two spin doublets with opposite momenta and a singlet for the neutral molecule. For benzene, the singlet (doublets) represent the ground state of the neutral (singly charged) molecule. We calculate the non-equilibrium conductance through a benzene molecule, doped with one electron or a hole (i.e. in the Kondo regime), and connected to two conducting leads at different positions. We solve the problem using the Keldysh formalism and the non-crossing approximation. When the leads are connected in the para position (at 180°), the model is equivalent to the ordinary impurity Anderson model and its known properties are recovered. For other positions, there is a partial destructive interference in the co-tunneling processes involving the two doublets and, as a consequence, the Kondo temperature and the height and width of the central peak (for bias voltage V(b) near zero) of the differential conductance G = dI/dV(b) (where I is the current) are reduced. In addition, two peaks at finite V(b) appear. We study the position of these peaks, the temperature dependence of G and the spectral densities. Our formalism can also be applied to carbon nanotube quantum dots with intervalley mixing.
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Nonequilibrium conductance of a nanodevice for small bias voltage. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:015306. [PMID: 22156237 DOI: 10.1088/0953-8984/24/1/015306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Using nonequilibrium renormalized perturbation theory, we calculate the retarded and lesser self-energies, the spectral density ρ(ω) near the Fermi energy, and the conductance G through a quantum dot as a function of a small bias voltage V, in the general case of electron-hole asymmetry and intermediate valence. The linear terms in ω and V are given exactly in terms of thermodynamic quantities. When the energies necessary to add the first electron (Ed) and the second one (Ed + U) to the quantum dot are not symmetrically placed around the Fermi level, G has a term linear in V if, in addition, either the voltage drop or the coupling to the leads is not symmetric. The effects of temperature are discussed. The results simplify for a symmetric voltage drop, a situation usual in experiment.
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Universal transport signatures in two-electron molecular quantum dots: gate-tunable Hund's rule, underscreened Kondo effect and quantum phase transitions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:243202. [PMID: 21625035 DOI: 10.1088/0953-8984/23/24/243202] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We review here some universal aspects of the physics of two-electron molecular transistors in the absence of strong spin-orbit effects. Several recent quantum dot experiments have shown that an electrostatic backgate could be used to control the energy dispersion of magnetic levels. We discuss how the generally asymmetric coupling of the metallic contacts to two different molecular orbitals can indeed lead to a gate-tunable Hund's rule in the presence of singlet and triplet states in the quantum dot. For gate voltages such that the singlet constitutes the (non-magnetic) ground state, one generally observes a suppression of low voltage transport, which can yet be restored in the form of enhanced cotunneling features at finite bias. More interestingly, when the gate voltage is controlled to obtain the triplet configuration, spin S = 1 Kondo anomalies appear at zero bias, with non-Fermi liquid features related to the underscreening of a spin larger than 1/2. Finally, the small bare singlet-triplet splitting in our device allows fine-tuning with the gate between these two magnetic configurations, leading to an unscreening quantum phase transition. This transition occurs between the non-magnetic singlet phase, where a two-stage Kondo effect occurs, and the triplet phase, where the partially compensated (underscreened) moment is akin to a magnetically 'ordered' state. These observations are put theoretically into a consistent global picture by using new numerical renormalization group simulations, tailored to capture sharp finite-voltage cotunneling features within the Coulomb diamonds, together with complementary out-of-equilibrium diagrammatic calculations on the two-orbital Anderson model. This work should shed further light on the complicated puzzle still raised by multi-orbital extensions of the classic Kondo problem.
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Spin-spin indirect interaction at low-energy excitation in zero-dimensional cavities. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:215304. [PMID: 21555830 DOI: 10.1088/0953-8984/23/21/215304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We solve the low-energy part of the spectrum of a model that describes a circularly polarized cavity mode strongly coupled to two exciton modes, each of which is coupled to a localized spin of arbitrary magnitude. In the regime in which the excitons and the cavity modes are strongly coupled, forming polaritons, the low-energy part of the spectrum can be described by an effective spin model, which contains a magnetic field, an axial anisotropy, and an Ising interaction between the localized spins. For detunings such that the low-energy states are dominated by nearly degenerate excitonic modes, the description of the low-energy states by a simple effective Hamiltonian ceases to be valid and the effective interaction tends to vanish. Finally, we discuss a possible application to two-qubit quantum computing operations in a system of transition-metal impurities embedded in quantum dots inside a micropillar.
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Mechanical Control of Spin States in Spin-1 Molecules and the Underscreened Kondo Effect. Science 2010; 328:1370-3. [DOI: 10.1126/science.1186874] [Citation(s) in RCA: 358] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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19
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Nonequilibrium dynamics of a singlet-triplet Anderson impurity near the quantum phase transition. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:025602. [PMID: 21386260 DOI: 10.1088/0953-8984/22/2/025602] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We study the singlet-triplet Anderson model (STAM) in which a configuration with a doublet is hybridized with another containing a singlet and a triplet, as a minimal model to describe two-level quantum dots coupled to two metallic leads in effectively a one-channel fashion. The model has a quantum phase transition which separates regions of a doublet and a singlet ground state. The limits of integer valence of the STAM (which include a model similar to the underscreened spin-1 Kondo model) are derived and used to predict the behavior of the conductance through the system on both sides of the transition, where it jumps abruptly. At a special quantum critical line, the STAM can be mapped to an infinite- U ordinary Anderson model (OAM) plus a free spin 1/2. We use this mapping to obtain the spectral densities of the STAM as a function of those of the OAM at the transition. Using the non-crossing approximation (NCA), we calculate the spectral densities and conductance through the system as a function of temperature and bias voltage, and determine the changes that take place at the quantum phase transition. The separation of the spectral density into a singlet and a triplet part allows us to shed light on the underlying physics and to explain a shoulder observed recently in the zero bias conductance as a function of temperature in transport measurements through a single fullerene molecule (Roch et al 2008 Nature 453 633). The structure with three peaks observed in nonequilibrium transport in these experiments is also explained.
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20
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Quantum interference in coherent molecular conductance. PHYSICAL REVIEW LETTERS 2009; 103:266807. [PMID: 20366334 DOI: 10.1103/physrevlett.103.266807] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Indexed: 05/29/2023]
Abstract
Coherent electronic transport through individual molecules is crucially sensitive to quantum interference. We investigate the zero-bias and zero-temperature conductance through pi-conjugated annulene molecules weakly coupled to two leads for different source-drain configurations, finding an important reduction for certain transmission channels and for particular geometries as a consequence of destructive quantum interference between states with definite momenta. When translational symmetry is broken by an external perturbation we find an abrupt increase of the conductance through those channels. Previous studies concentrated on the effect at the Fermi energy, where this effect is very small. By analyzing the effect of symmetry breaking on the main transmission channels we find a much larger response thus leading to the possibility of a larger switching of the conductance through single molecules.
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21
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Photoluminescence of a quantum dot hybridized with a continuum of extended states. PHYSICAL REVIEW LETTERS 2009; 103:156802. [PMID: 19905656 DOI: 10.1103/physrevlett.103.156802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2009] [Indexed: 05/28/2023]
Abstract
We calculate the intensity of photon emission from a trion in a single quantum dot, as a function of energy and gate voltage, using the impurity Anderson model and variational wave functions. Assuming a flat density of conduction states and constant hybridization energy, the results agree with the main features observed in recent experiments: nonmonotonic dependence of the energy on gate voltage, non-Lorentzian line shapes, and a linewidth that increases near the regions of instability of the single electron final state to occupations zero or two.
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22
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Dynamical mean field theory of an effective three-band model for NaxCoO2. PHYSICAL REVIEW LETTERS 2009; 102:066402. [PMID: 19257613 DOI: 10.1103/physrevlett.102.066402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2008] [Indexed: 05/27/2023]
Abstract
We derive an effective Hamiltonian for highly correlated t_{2g} states centered at the Co sites of NaxCoO2. The essential ingredients of the model are an O mediated hopping, a trigonal crystal-field splitting, and on-site effective interactions derived from the exact solution of a multiorbital model in a CoO6 cluster, with parameters determined previously. The effective model is solved by dynamical mean field theory. We obtain a Fermi surface and electronic dispersion that agrees well with angle-resolved photoemission spectra. Our results also elucidate the origin of the "sinking pockets" in different doping regimes.
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23
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Ferrotoroidic moment as a quantum geometric phase. PHYSICAL REVIEW LETTERS 2008; 101:077203. [PMID: 18764574 DOI: 10.1103/physrevlett.101.077203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2008] [Indexed: 05/26/2023]
Abstract
We present a geometric characterization of the ferrotoroidic moment tau in terms of a set of Abelian Berry phases. We also introduce a fundamental complex quantity z munu, which provides an alternative way to calculate tau and its moments and is derived from the tensor T munu=2 under summation operator jrj muSj nu. This geometric framework defines a natural computational approach for density functional and many-body theories.
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Effects of interactions in transport through Aharonov-Bohm-Casher interferometers. PHYSICAL REVIEW LETTERS 2008; 100:016803. [PMID: 18232803 DOI: 10.1103/physrevlett.100.016803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2007] [Indexed: 05/25/2023]
Abstract
We study the conductance through a ring described by the Hubbard model (such as an array of quantum dots), threaded by a magnetic flux and subject to Rashba spin-orbit coupling (SOC). We develop a formalism that is able to describe the interference effects as well as the Kondo effect when the number of electrons in the ring is odd. In the Kondo regime, the SOC reduces the conductance from the unitary limit, and, in combination with the magnetic flux, the device acts as a spin polarizer.
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25
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Comment on "Zero-field Kondo Splitting and Quantum-Critical Transition in Double Quantum Dots". PHYSICAL REVIEW LETTERS 2007; 99:209701-209702. [PMID: 18233193 DOI: 10.1103/physrevlett.99.209701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2007] [Indexed: 05/25/2023]
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26
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Incommmensurability and unconventional superconductor to insulator transition in the hubbard model with bond-charge interaction. PHYSICAL REVIEW LETTERS 2007; 99:206401. [PMID: 18233165 DOI: 10.1103/physrevlett.99.206401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2007] [Indexed: 05/25/2023]
Abstract
We determine the quantum phase diagram of the one-dimensional Hubbard model with bond-charge interaction X in addition to the usual Coulomb repulsion U>0 at half-filling. For large enough X<t the model shows three phases. For large U the system is in the spin-density wave phase as in the usual Hubbard model. As U decreases, there is first a spin transition to a spontaneously dimerized bond-ordered wave phase and then a charge transition to a novel phase in which the dominant correlations at large distances correspond to an incommensurate singlet superconductor.
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Theory of polariton-mediated Raman scattering in microcavities. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2007; 19:176210. [PMID: 21690956 DOI: 10.1088/0953-8984/19/17/176210] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We calculate the intensity of the polariton-mediated inelastic light scattering in semiconductor microcavities. We treat the exciton-photon coupling nonperturbatively and incorporate lifetime effects in both excitons and photons, and a coupling of the photons to the electron-hole continuum. Taking the matrix elements as fitting parameters, the results are in excellent agreement with measured Raman intensities due to optical phonons that are resonant with the upper polariton branches in II-VI microcavities with embedded CdTe quantum wells.
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Effective Kondo model for a trimer on a metallic surface. PHYSICAL REVIEW LETTERS 2006; 96:096804. [PMID: 16606296 DOI: 10.1103/physrevlett.96.096804] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2005] [Indexed: 05/08/2023]
Abstract
I consider a Hubbard-Anderson model which describes localized orbitals in three different atoms hybridized both among themselves and with a continuum of extended states. Using a generalized Schrieffer-Wolf transformation, I derive an effective Kondo model for the interaction between the doublet ground state of the isolated trimer and the extended states. For an isoceles trimer with distances a, l, l between the atoms, the Kondo temperature is very small for l<a and has a maximum for finite l>a when a is small. The results agree with experiments for a Cr trimer on Au(111).
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Detection of topological transitions by transport through molecules and nanodevices. PHYSICAL REVIEW LETTERS 2004; 93:076801. [PMID: 15324262 DOI: 10.1103/physrevlett.93.076801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2003] [Indexed: 05/24/2023]
Abstract
We analyze the phase transitions of an interacting electronic system weakly coupled to free-electron leads by considering its zero-bias conductance. This is expressed in terms of two effective impurity models for the cases with and without spin degeneracy. Using the half-filled ionic Hubbard ring, we demonstrate that the weight of the first conductance peak as a function of external flux or of the difference in gate voltages between even and odd sites allows one to identify the topological charge transition between a correlated insulator and a band insulator.
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Spin-charge separation in Aharonov-Bohm rings of interacting electrons. PHYSICAL REVIEW LETTERS 2004; 93:067203. [PMID: 15323659 DOI: 10.1103/physrevlett.93.067203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2004] [Indexed: 05/24/2023]
Abstract
We investigate the properties of strongly correlated electronic models on a flux-threaded ring connected to semi-infinite free-electron leads. The interference pattern of such an Aharonov-Bohm ring shows sharp dips at certain flux values, determined by the filling, which are a consequence of spin-charge separation in a nanoscopic system.
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Exact bond ordered ground state for the transition between the band and the Mott insulator. PHYSICAL REVIEW LETTERS 2004; 92:246405. [PMID: 15245117 DOI: 10.1103/physrevlett.92.246405] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2003] [Indexed: 05/24/2023]
Abstract
We derive an effective Hamiltonian H(eff) for an ionic Hubbard chain, valid for t<<U,Delta, where t is the hopping, U is the Coulomb repulsion, and Delta is the charge-transfer energy. H(eff) is the minimal model for describing the transition between the band insulator (BI) (Delta-U>>t) and the Mott insulator (MI) (U-Delta>>t). Using spin-particle transformations [Phys. Rev. Lett. 86, 1082 (2001)]], we map H(eff)(U=Delta) into an SU(3) antiferromagnetic Heisenberg model whose exact ground state is known. In this way, we show rigorously that a spontaneously dimerized insulating ferroelectric phase appears in the transition region between the BI and the MI.
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Anomalous flux quantization in a hubbard ring with correlated hopping. PHYSICAL REVIEW LETTERS 1996; 76:4396-4399. [PMID: 10061279 DOI: 10.1103/physrevlett.76.4396] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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34
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Phase separation and valence instabilities in cuprate superconductors: Effective one-band-model approach. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 53:15327-15334. [PMID: 9983331 DOI: 10.1103/physrevb.53.15327] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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35
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Magnetic, nonmagnetic, and non-Fermi-liquid ground state of an impurity fluctuating between two magnetic configurations. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:12497-12500. [PMID: 9980397 DOI: 10.1103/physrevb.52.12497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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36
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Electronic structure of the CuO3 chains in RBa2Cu3O6+x (R=Y or a rare earth). PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:13601-13604. [PMID: 9980558 DOI: 10.1103/physrevb.52.13601] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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37
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Erratum: Superconducting correlations in Hubbard chains with correlated hopping. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:9793. [PMID: 9980031 DOI: 10.1103/physrevb.52.9793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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38
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Ground state and magnetic susceptibility of intermediate-valence Tm impurities. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:7987-7993. [PMID: 9979797 DOI: 10.1103/physrevb.52.7987] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Superconductivity from correlated hopping. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:6223-6226. [PMID: 9981849 DOI: 10.1103/physrevb.52.6223] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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40
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Derivation and numerical study of the singlet-triplet model for cuprate superconductors. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:7701-7707. [PMID: 9979715 DOI: 10.1103/physrevb.52.7701] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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41
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Long-range Coulomb repulsion and finite-size approximations. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:6227-6229. [PMID: 9981850 DOI: 10.1103/physrevb.52.6227] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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42
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Brinkman-Rice transition driven by interatomic repulsion in hexagonal copper oxides. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 51:15642-15644. [PMID: 9978540 DOI: 10.1103/physrevb.51.15642] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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43
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Single-particle spectral function of a generalized Hubbard model: Metal-insulator transition. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 51:14012-14019. [PMID: 9978326 DOI: 10.1103/physrevb.51.14012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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44
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Phase diagram of an extended Hubbard model with correlated hopping at half filling. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 51:13774-13777. [PMID: 9978183 DOI: 10.1103/physrevb.51.13774] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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45
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Superconducting correlations in Hubbard chains with correlated hopping. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 50:16044-16051. [PMID: 9975976 DOI: 10.1103/physrevb.50.16044] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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46
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Exact solution of a Hubbard chain with bond-charge interaction. PHYSICAL REVIEW LETTERS 1994; 73:2240-2243. [PMID: 10057008 DOI: 10.1103/physrevlett.73.2240] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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47
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Mechanism for electric field effects observed in YBa2Cu3O7-x films. PHYSICAL REVIEW LETTERS 1994; 73:1561. [PMID: 10056824 DOI: 10.1103/physrevlett.73.1561] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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48
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Effect of the Cu-Cu superexchange on the stability of Zhang-Rice singlets. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 49:16048-16051. [PMID: 10010746 DOI: 10.1103/physrevb.49.16048] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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49
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Systematic derivation of a generalized t-J model. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 49:13061-13064. [PMID: 10010218 DOI: 10.1103/physrevb.49.13061] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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