O. Entin-Wohlman

University of Science and Technology of China, Luchow, Anhui Sheng, China

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Publications (253)479.21 Total impact

  • Source
    Y. Utsumi, O. Entin-Wohlman, A. Aharony, T. Kubo, Y. Tokura
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    ABSTRACT: We analyze the full-counting statistics of the electric heat current flowing in a two-terminal quantum conductor whose temperature is probed by a third electrode (``probe electrode"). In particular we demonstrate that the cumulant-generating function obeys the fluctuation theorem in the presence of a constant magnetic field. The analysis is based on the scattering matrix of the three-terminal junction (comprising of the two electronic terminals and the probe electrode), and a separation of time scales: it is assumed that the rapid charge transfer across the conductor and the rapid relaxation of the electrons inside the probe electrode give rise to much slower energy fluctuations in the latter. This separation allows for a stochastic treatment of the probe dynamics, and the reduction of the three-terminal setup to an effective two-terminal one. Expressions for the lowest nonlinear transport coefficients, e.g., the linear-response heat-current noise and the second nonlinear thermal conductance, are obtained and explicitly shown to preserve the symmetry of the fluctuation theorem for the two-terminal conductor. The derivation of our expressions which is based on the transport coefficients of the three-terminal system explicitly satisfying the fluctuation theorem, requires the full calculations of vertex corrections.
    03/2014;
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    R. I. Shekhter, O. Entin-Wohlman, A. Aharony
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    ABSTRACT: A device enabling mechanically-controlled spin and electric transport in mesoscopic structures is proposed. It is based on the transfer of electrons through weak links formed by suspended nanowires, on which the charge carriers experience a strong Rashba spin-orbit interaction that twists their spins. It is demonstrated that when the weak link bridges two magnetically-polarised electrodes, a significant spintro-voltaic effect takes place. Then, by monitoring the generated voltage one is able to measure electronic spins accumulated in the electrodes, induced e.g., by circularly-polarised light, or alternatively, the amount of spin twisting. Mechanically-tuning the device by bending the nanowire allows one to achieve full control over the spin orientations of the charge carriers.
    03/2014;
  • O Entin-Wohlman, Y Imry
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    ABSTRACT: A Comment on the Letter by B. Cleuren et. al., Phys. Rev. Lett. 108 120603 (2012). The authors of the Letter offer a Reply.
    Physical Review Letters 01/2014; 112(4):048901. · 7.94 Impact Factor
  • Source
    O Entin-Wohlman, J-H Jiang, Y Imry
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    ABSTRACT: The efficiency and cooling power of a two-terminal thermoelectric refrigerator are analyzed near the limit of vanishing dissipation (ideal system), where the optimal efficiency is the Carnot one, but the cooling power vanishes. This limit, where transport occurs only via a single sharp electronic energy, has been referred to as "strong coupling" or "the best thermoelectric." Confining the discussion to the linear-response regime, it is found that "parasitic" effects that make the system deviate from the ideal limit, and reduce the efficiency from the Carnot limit, are crucial for the usefulness of the device. Among these parasitics, there are: parallel phonon conduction, finite width of the electrons' transport band, and more than a single energy transport channel. In terms of a small parameter characterizing the deviation from the ideal limit, the efficiency and power grow linearly, and the dissipation quadratically. The results are generalized to the case of broken time-reversal symmetry, and the major nontrivial changes are discussed. Finally, the recent universal relation between the thermopower and the asymmetry of the dissipation between the two terminals is briefly discussed, including the small dissipation limit.
    Physical Review E 01/2014; 89(1-1):012123. · 2.31 Impact Factor
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    ABSTRACT: Recent experiments [M. Yamamoto et al., Nature Nanotechnology 7, 247 (2012)] used the transport of electrons through an Aharonov-Bohm interferometer and two coupled channels (at both ends of the interferometer) to demonstrate a manipulable flying qubit. Results included in-phase and anti-phase Aharonov-Bohm (AB) oscillations of the two outgoing currents as a function of the magnetic flux, for strong and weak inter-channel coupling, respectively. Here we present new experimental results for a three terminal interferometer, with a tunnel coupling between the two outgoing wires. We show that in some limits, this system is an even simpler realization of the "two-slit" experiment. We also present a simple tight- binding theoretical model which imitates the experimental setup. For weak inter-channel coupling, the AB oscillations in the current which is reflected from the device are very small, and therefore the oscillations in the two outgoing currents must cancel each other, yielding the anti-phase behavior, independent of the length of the coupling regime. For strong inter-channel coupling, whose range depends on the asymmetry between the channels, and for a relatively long coupling distance, all except two of the waves in the coupled channels become evanescent. For the remaining running waves one has a very weak dependence of the ratio between the currents in the two channels on the magnetic flux, implying that these currents are in phase with each other.
    12/2013;
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    ABSTRACT: We study the spin-dependent transport of spin-1/2 electrons through an interferometer made of two elongated quantum dots or quantum nanowires, which are subject to both an Aharonov-Bohm flux and (Rashba and Dresselhaus) spin-orbit interactions. Similar to the diamond interferometer proposed in our previous papers [Phys. Rev. B {\bf 84}, 035323 (2011); Phys. Rev. B {\bf 87}, 205438 (2013)], we show that the double-dot interferometer can serve as a perfect spin filter due to a spin interference effect. By appropriately tuning the external electric and magnetic fields which determine the Aharonov-Casher and Aharonov-Bohm phases, and with some relations between the various hopping amplitudes and site energies, the interferometer blocks electrons with a specific spin polarization, independent of their energy. The blocked polarization and the polarization of the outgoing electrons is controlled solely by the external electric and magnetic fields and do not depend on the energy of the electrons. Furthermore, the spin filtering conditions become simpler in the linear-response regime, in which the electrons have a fixed energy. Unlike the diamond interferometer, spin filtering in the double-dot interferometer does not require high symmetry between the hopping amplitudes and site energies of the two branches of the interferometer and thus may be more appealing from an experimental point of view.
    New Journal of Physics 12/2013; 15(125017). · 4.06 Impact Factor
  • Source
    O. Entin-Wohlman, Y. Imry
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    ABSTRACT: We reanalyse the work of Cleuren et al., Phys. Rev. Lett. 109, 248902 (2012), in the light of Jiang et al. Phys. Rev. B 85, 075412 (2012). The condition for cooling enforces its rate to be exponentially small at low temperatures. Thus, the difficulty with the "dynamic version of the third law" found by Levy et al., Phys. Rev. Lett. 109, 248901 (2012) and Allahverdyan et al., Phys. Rev. Lett. 109, 248903 (2012) is resolved.
    11/2013;
  • R I Shekhter, O Entin-Wohlman, A Aharony
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    ABSTRACT: Suspended nanowires are shown to provide mechanically controlled coherent mixing or splitting of the spin states of transmitted electrons, caused by the Rashba spin-orbit interaction. The sensitivity of the latter to mechanical bending makes the wire a tunable nanoelectromechanical weak link between reservoirs. When the reservoirs are populated with misbalanced "spin-up and spin-down" electrons, the wire becomes a source of split spin currents, which are not associated with electric charge transfer and which do not depend on temperature or driving voltages. The mechanical vibrations of the bended wires allow for additional tunability of these splitters by applying a magnetic field and varying the temperature. Clean metallic carbon nanotubes of a few microns length are good candidates for generating spin conductance of the same order as the charge conductance (divided by e^{2}) which would have been induced by electric driving voltages.
    Physical Review Letters 10/2013; 111(17):176602. · 7.94 Impact Factor
  • O. Entin-Wohlman, A. Aharony, Y. Imry
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    ABSTRACT: Two important features of mesoscopic Aharonov-Bohm (A-B) electronic interferometers are analyzed: decoherence due to coupling with other degrees of freedom and the coupled transport of charge and heat. We first review the principles of decoherence of electronic interference. We then analyze the thermoelectric transport in a ring threaded by such a flux, with a molecular bridge on one of its arms. The charge carriers may also interact inelastically with the molecular vibrations. This nano-system is connected to three termi- nals; two of them are electric and thermal, held at slightly different chemical potentials and temperatures, and the third is purely thermal. For example, a phonon bath thermalizing the molecular vibrations. When this third terminal is held at a temperature different from those of the electronic reservoirs, both an electrical and a heat current are, in general, gen- erated between the latter. Likewise, a voltage and/or temperature difference between the electronic terminals leads to thermal current between the thermal and electronic terminals. The transport coefficients governing these conversions (due to energy exchange between the electrons and the vibrations) and their dependences on the A-B flux are analyzed. Finally, the decoherence due to these inelastic events is discussed.
    06/2013;
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    ABSTRACT: In an earlier paper [Phys. Rev. B 84, 035323 (2011)], we proposed a spin filter which was based on a diamond-like interferometer, subject to both an Aharonov-Bohm flux and (Rashba and Dresselhaus) spin-orbit interactions. Here we show that the full polarization of the outgoing electron spins remains the same even when one allows leakage of electrons from the branches of the interferometer. Once the gate voltage on one of the branches is tuned to achieve an effective symmetry between them, this polarization can be controlled by the electric and/or magnetic fields which determine the spin-orbit interaction strength and the Aharonov-Bohm flux.
    Physical review. B, Condensed matter 05/2013; 87(205438).
  • Source
    Jian-Hua Jiang, Ora Entin-Wohlman, Yoseph Imry
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    ABSTRACT: A three-terminal thermoelectric device based on a $p$-$i$-$n$ semiconductor junction is proposed, where the intrinsic region is mounted onto a, typically bosonic, thermal terminal. Remarkably, the figure of merit of the device is governed also by the energy distribution of the {\em bosons} participating in the transport processes, in addition to the electronic one. An enhanced figure of merit can be obtained when the relevant distribution is narrow and the electron-boson coupling is strong (such as for optical phonons). We study the conditions for which the figure of merit of the three-terminal junction can be greater than those of the usual thermoelectric devices made of the same material. A possible setup with a high figure of merit, based on Bi$_2$Te$_3$/Si superlattices, is proposed.
    New Journal of Physics 05/2013; 15(7). · 4.06 Impact Factor
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    H Bary-Soroker, O Entin-Wohlman, Y Imry, A Aharony
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    ABSTRACT: The interaction-induced orbital magnetic response of a nanoscale system, modeled by the persistent current in a ring geometry, is evaluated for a system which is a superconductor in the bulk. The interplay of the renormalized Coulomb and Fröhlich interactions is crucial. The diamagnetic response of the large superconductor may become paramagnetic when the finite-size-determined Thouless energy is larger than or on the order of the Debye energy.
    Physical Review Letters 02/2013; 110(5):056801. · 7.94 Impact Factor
  • Source
    J. -H. Jiang, O. Entin-Wohlman, Y. Imry
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    ABSTRACT: It is shown that for the hopping regime, the thermopowers in both finite two-terminal and three-terminal systems are governed by the edges of the samples. This is due to the fact that the energy transfer between a transport electron and a conducting terminal is determined by the site most strongly coupled to that terminal. One-dimensional systems with both nearest-neighbor and variable-range transport as well as certain types of two-dimensional systems, are considered. For a given sample, the changes in the thermopowers due to modifying the bulk are quite limited, compared with those of the conductance. When the small thermopower changes exist, their average over a large ensemble of mesoscopic samples will vanish. We also obtain the distribution of the thermopower in such an ensemble and show that its width approaches a finite limit with increasing sample length. This contrasts with the distribution of conductances in such systems, whose width vanishes in the long sample limit. Finally, we find that the thermal conductances in the three-terminal case have a boundary-dominated contribution, due to non-percolating conduction paths. This contribution can become dominant when the usual conductance is small enough. All our theoretical statements are backed by numerical computations.
    Physical review. B, Condensed matter 01/2013; 87(20).
  • Source
    Y. Utsumi, O. Entin-Wohlman, A. Ueda, A. Aharony
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    ABSTRACT: We study the full-counting statistics of charges transmitted through a single-level quantum dot weakly coupled to a local Einstein phonon which causes fluctuations in the dot energy. An analytic expression for the cumulant generating function, accurate up to second order in the electron-phonon coupling and valid for finite voltages and temperatures, is obtained in the extended wide-band limit. The result accounts for nonequilibrium phonon distributions induced by the source-drain bias voltage, and concomitantly satisfies the fluctuation theorem. Extending the counting field to the complex plane, we investigate the locations of possible singularities of the cumulant generating function, and exploit them to identify regimes in which the electron transfer is affected differently by the coupling to the phonons. Within a large-deviation analysis, we find a kink in the probability distribution, analogous to a first-order phase transition in thermodynamics, which would be a unique hallmark of the electron-phonon correlations. This kink reflects the fact that although inelastic scattering by the phonons once the voltage exceeds their frequency can scatter electrons opposite to the bias, this will never generate current flowing against the bias at zero temperature, in accordance with the fluctuation theorem.
    Physical review. B, Condensed matter 10/2012; 87(11).
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    Yuval B. Simons, Ora Entin-Wohlman, Yuval Oreg, Yoseph Imry
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    ABSTRACT: Reentrant behavior is known to exist and magnetic-field-induced superconductivity has been predicted in superconductors with Kondo impurities. We present a simple framework for understanding these phenomena and generalize it to explain the long-standing puzzle of paramagnetic reentrance in thick proximity systems as being due to Kondo impurities.
    Physical review. B, Condensed matter 08/2012; 86(6).
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    Shlomi Matityahu, Amnon Aharony, Ora Entin-Wohlman
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    ABSTRACT: We present a theoretical analysis of the temperature magnetic field concentration phase diagram of the multiferroic Mn1−xMxWO4 (M= Fe, Zn, Mg), which exhibits three ordered phases, with collinear and noncollinear incommensurate and with a commensurate magnetic order. The middle phase is also ferroelectric. The analysis uses a semiphenomenological Landau theory based on a Heisenberg Hamiltonian with a single-ion anisotropy. With a small number of adjustable parameters, the Landau theory gives an excellent fit to all three transition lines as well as the magnetic and the ferroelectric order parameters. The fit of the magnetic and ferroelectric order parameters is further improved by including the effect of fluctuations near the transitions. We demonstrate the highly frustrated nature of these materials and suggest a simple explanation for the dramatic effects of doping with different magnetic ions at the Mn sites. The model enables an examination of different sets of exchange couplings that were proposed by a number of groups. Small discrepancies are probably a consequence of small errors in the experimental magnetic parameters. In addition, using the Ginzburg criterion, we estimate the temperature range in which fluctuations of the order parameters become important.
    Physical review. B, Condensed matter 05/2012; 85(174408).
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    ABSTRACT: Real-time nonequilibrium quantum dynamics of electrons in double-dot Aharonov-Bohm (AB) interferometers is studied using an exact solution of the master equation. The building of the coherence between the two electronic paths shows up via the time-dependent amplitude of the AB oscillations in the transient transport current, and can be enhanced by varying the applied bias on the leads, the on-site energy difference between the dots and the asymmetry of the coupling of the dots to the leads. The transient oscillations of the transport current do not obey phase rigidity. The circulating current has an anti-symmetric AB oscillation in the flux. The non-degeneracy of the on-site energies and the finite bias cause the occupation in each dot to have an arbitrary flux dependence as the coupling asymmetry is varied.
    Physical review. B, Condensed matter 05/2012; 86(11).
  • Source
    A. Aharony, O. Entin-Wohlman, H. Bary-Soroker, Y. Imry
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    ABSTRACT: The contributions of superconducting fluctuations to the specific heat of dirty superconductors are calculated, including quantum and classical corrections to the `usual' leading Gaussian divergence. These additional terms modify the Ginzburg criterion, which is based on equating these fluctuation-generated contributions to the mean-field discontinuity in the specific heat, and set limits on its applicability for materials with a low transition temperature.
    Lithuanian Journal of Physics and Technical Sciences. 02/2012; 52(2).
  • O. Entin-Wohlman
    [show abstract] [hide abstract]
    ABSTRACT: The thermoelectric transport through a ring threaded by an Aharonov-Bohm flux, with a molecular bridge on one of its arms, is analyzed. The charge carriers also interact with the vibrational excitations of that molecule. This nanosystem is connected to three terminals: two are electronic reservoirs, which supply the charge carriers, and the third is the phonon bath which thermalizes the molecular vibrations. Expressions for the transport coefficients, relating all charge and heat currents to the temperature and chemical potential differences between the terminals, are derived to second order in the electron-vibration coupling. At linear response, all these coefficients obey the full Onsager-Casimir relations. When the phonon bath is held at a temperature different from those of the electronic reservoirs, a heat current exchanged between the molecular vibrations and the charge carriers can be converted into electric and/or heat electronic currents. The related transport coefficients, which exist only due to the electron-vibration coupling, change sign under the interchange between the electronic terminals and the sign change of the magnetic flux. It is also demonstrated that the Aharonov-Bohm flux can enhance this type of conversion.
    Physical review. B, Condensed matter 02/2012; 85(8).
  • Source
    Jian-Hua Jiang, Ora Entin-Wohlman, Yoseph Imry
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    ABSTRACT: A two-site nanostructure (e.g, a "molecule") bridging two conducting leads and connected to a phonon bath is considered. The two relevant levels closest to the Fermi energy are connected each to its lead. The leads have slightly different temperatures and chemical potentials and the nanos- tructure is also coupled to a thermal (third) phonon bath. The 3 x 3 linear transport ("Onsager") matrix is evaluated, along with the ensuing new figure of merit, and found to be very favorable for thermoelectric energy conversion.
    Physical review. B, Condensed matter 01/2012; 85(7).

Publication Stats

1k Citations
479.21 Total Impact Points

Institutions

  • 2013
    • University of Science and Technology of China
      • Department of Physics
      Luchow, Anhui Sheng, China
  • 2004–2013
    • Ben-Gurion University of the Negev
      • Department of Physics
      Beersheba, Southern District, Israel
  • 1973–2013
    • Tel Aviv University
      • Department of Physics and Astronomy
      Tell Afif, Tel Aviv, Israel
  • 2004–2009
    • Weizmann Institute of Science
      • • Department of Physics of Condensed Matter
      • • Albert Einstein Minerva Center for Theoretical Physics
      Be'er Sheva`, Southern District, Israel
  • 2008
    • University of Pennsylvania
      • Department of Physics and Astronomy
      Philadelphia, PA, United States
  • 2005
    • The University of Tokyo
      • Institute for Solid State Physics
      Tokyo, Tokyo-to, Japan
  • 2004–2005
    • Los Alamos National Laboratory
      Los Alamos, California, United States
  • 2001
    • University of Toronto
      Toronto, Ontario, Canada
  • 2000
    • Norwegian Theatre Academy
      Fredrikshald, Østfold, Norway
    • Brookhaven National Laboratory
      New York City, New York, United States
  • 1983–2000
    • Hebrew University of Jerusalem
      • Racah Institute of Physics
      Jerusalem, Jerusalem District, Israel
  • 1990
    • University of Cologne
      • Institute for Theoretical Physics
      Köln, North Rhine-Westphalia, Germany
  • 1976–1989
    • University of California, Los Angeles
      Los Angeles, California, United States
  • 1985
    • Bar Ilan University
      • Department of Physics
      Ramat Gan, Tel Aviv, Israel