The Experts below are selected from a list of 990 Experts worldwide ranked by ideXlab platform
Ali Shakouri - One of the best experts on this subject based on the ideXlab platform.
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nonlinear Peltier effect in semiconductors
2007Co-Authors: Mona Zebarjadi, Keiva Esfarjani, Ali ShakouriAbstract:Nonlinear Peltier Coefficient of a doped InGaAs semiconductor is calculated numerically using the Monte Carlo technique. The Peltier Coefficient is also obtained analytically for single parabolic band semiconductors assuming a shifted Fermi-Dirac electronic distribution under an applied bias. Analytical results are in agreement with numerical simulations. Key material parameters affecting the nonlinear behavior are doping concentration, effective mass, and electron-phonon coupling. Current density thresholds at which nonlinear behavior is observable are extracted from numerical data. It is shown that the nonlinear Peltier effect can be used to enhance cooling of thin film microrefrigerator devices especially at low temperatures.
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bias dependent Peltier Coefficient and internal cooling in bipolar devices
2002Co-Authors: Kevin P Pipe, Rajeev J Ram, Ali ShakouriAbstract:The work described here is an investigation of thermoelectric phenomena in bipolar semiconductors and $p\ensuremath{-}n$ junctions. In contrast to majority-carrier semiconductors in which a constant material-dependent Peltier Coefficient is defined for a given temperature, bipolar devices can be modeled by introducing a bias-dependent Peltier Coefficient at interfaces that takes into account the variation of the carriers' average transport energy. It is shown that this effective Peltier Coefficient can vary by orders of magnitude as a function of applied bias, and can give rise to interfacial thermoelectric cooling or heating depending on device parameters. The bias-dependent bipolar Peltier Coefficient is modeled analytically for short-length and long-length diodes, and the different regimes of bias for which cooling is achieved are described, as well as the effects of recombination, length, and doping. Analytical expressions to optimize the thermoelectric effect inside an idealized diode cooler are presented with numerical results for several common semiconductors, a figure of merit for internal diode cooling is introduced, and extensions of the model are given for applications such as the internal cooling of a semiconductor laser diode.
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bias dependent Peltier Coefficient in bipolar devices
2001Co-Authors: Kevin P Pipe, Ali Shakouri, Rajeev J Ram, Jack BaskinAbstract:Temperature stabilization is important in many microelectronic devices due to thermal constraints on device operation and lifetime. The work described here is an investigation of thermoelectric phenomena in bipolar devices, speci£cally the p-n diode. Current injection can modify the Peltier coef£cient at interfaces; this can give rise to thermoelectric cooling or heating depending on device parameters. The bias-dependent Peltier coef£cient is modeled using self-consistent drift-diffusion, and implications for device design are examined. The different regimes of bias for which cooling is achieved are described, as well as the effects of device length, doping, and heterojunction band offset. Extensions of the model are given for applications such as the internal cooling of semiconductor laser diodes.
Ken-ichi Uchida - One of the best experts on this subject based on the ideXlab platform.
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High-throughput imaging measurements of thermoelectric figure of merit
2021Co-Authors: Abdulkareem Alasli, Ryo Iguchi, Asuka Miura, Hosei Nagano, Ken-ichi UchidaAbstract:We demonstrate a method for the simultaneous determination of the thermoelectric of merit of multiple martials by means of the lock-in thermography (LIT) technique. This method is based on the thermal analyses of the transient temperature distribution induced by the Peltier effect and Joule heating, which enables high-throughput estimation of the thermal diffusivity, thermal conductivity, volumetric heat capacity, Seebeck or Peltier Coefficient of the materials. The LIT-based approach has high reproducibility and reliability because it offers sensitive noncontact temperature measurements and does not require the installation of an external heater. By performing the same measurements and analyses with applying an external magnetic field, the magnetic field and/or magnetization dependences of the Seebeck or Peltier Coefficient and thermal conductivity can be determined simultaneously. We demonstrate the validity of this method by using several ferromagnetic metals (Ni, Ni95Pt5, and Fe) and a nonmagnetic metal (Ti). The proposed method will be useful for materials research in thermoelectrics and spin caloritronics and for investigation of magneto-thermal and magneto-thermoelectric transport properties.
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first principles study of the anisotropic magneto Peltier effect
2019Co-Authors: Keisuke Masuda, Ryo Iguchi, Ken-ichi Uchida, Yoshio MiuraAbstract:We study theoretically the anisotropic magneto-Peltier effect, which was recently demonstrated experimentally. A first-principles-based Boltzmann transport approach including the spin-orbit interaction shows that Ni has a larger anisotropy of the Peltier Coefficient ($\Delta \Pi$) than Fe, consistent with experiments. It is clarified that spin-flip electron transitions due to the spin-orbit interaction are the key in the mechanism of the large anisotropic magneto-Peltier effect. Using our method, we further predict several ferromagnetic metals with much larger $\Delta \Pi$ than that of Ni.
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observation of anisotropic magneto Peltier effect in nickel
2018Co-Authors: Ken-ichi Uchida, Ryo Iguchi, Shunsuke Daimo, Eiji SaitohAbstract:The Peltier effect, discovered in 1834, converts a charge current into a heat current in a conductor, and its performance is described by the Peltier Coefficient, which is defined as the ratio of the generated heat current to the applied charge current1,2. To exploit the Peltier effect for thermoelectric cooling or heating, junctions of two conductors with different Peltier Coefficients have been believed to be indispensable. Here we challenge this conventional wisdom by demonstrating Peltier cooling and heating in a single material without junctions. This is realized through an anisotropic magneto-Peltier effect in which the Peltier Coefficient depends on the angle between the directions of a charge current and magnetization in a ferromagnet. By using active thermography techniques3–10, we observe the temperature change induced by this effect in a plain nickel slab. We find that the thermoelectric properties of the ferromagnet can be redesigned simply by changing the configurations of the charge current and magnetization, for instance, by shaping the ferromagnet so that the current must flow around a curve. Our experimental results demonstrate the suitability of nickel for the anisotropic magneto-Peltier effect and the importance of spin–orbit interaction in its mechanism. The anisotropic magneto-Peltier effect observed here is the missing thermoelectric phenomenon in ferromagnetic materials—the Onsager reciprocal of the anisotropic magneto-Seebeck effect previously observed in ferromagnets—and its simplicity might prove useful in developing thermal management technologies for electronic and spintronic devices. A ‘magneto-Peltier effect’ produces cooling or heating in a material without junctions, by forcing a change in angle between the current and magnetization in a single ferromagnetic nickel slab.
Ryo Iguchi - One of the best experts on this subject based on the ideXlab platform.
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High-throughput imaging measurements of thermoelectric figure of merit
2021Co-Authors: Abdulkareem Alasli, Ryo Iguchi, Asuka Miura, Hosei Nagano, Ken-ichi UchidaAbstract:We demonstrate a method for the simultaneous determination of the thermoelectric of merit of multiple martials by means of the lock-in thermography (LIT) technique. This method is based on the thermal analyses of the transient temperature distribution induced by the Peltier effect and Joule heating, which enables high-throughput estimation of the thermal diffusivity, thermal conductivity, volumetric heat capacity, Seebeck or Peltier Coefficient of the materials. The LIT-based approach has high reproducibility and reliability because it offers sensitive noncontact temperature measurements and does not require the installation of an external heater. By performing the same measurements and analyses with applying an external magnetic field, the magnetic field and/or magnetization dependences of the Seebeck or Peltier Coefficient and thermal conductivity can be determined simultaneously. We demonstrate the validity of this method by using several ferromagnetic metals (Ni, Ni95Pt5, and Fe) and a nonmagnetic metal (Ti). The proposed method will be useful for materials research in thermoelectrics and spin caloritronics and for investigation of magneto-thermal and magneto-thermoelectric transport properties.
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first principles study of the anisotropic magneto Peltier effect
2019Co-Authors: Keisuke Masuda, Ryo Iguchi, Ken-ichi Uchida, Yoshio MiuraAbstract:We study theoretically the anisotropic magneto-Peltier effect, which was recently demonstrated experimentally. A first-principles-based Boltzmann transport approach including the spin-orbit interaction shows that Ni has a larger anisotropy of the Peltier Coefficient ($\Delta \Pi$) than Fe, consistent with experiments. It is clarified that spin-flip electron transitions due to the spin-orbit interaction are the key in the mechanism of the large anisotropic magneto-Peltier effect. Using our method, we further predict several ferromagnetic metals with much larger $\Delta \Pi$ than that of Ni.
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observation of anisotropic magneto Peltier effect in nickel
2018Co-Authors: Ken-ichi Uchida, Ryo Iguchi, Shunsuke Daimo, Eiji SaitohAbstract:The Peltier effect, discovered in 1834, converts a charge current into a heat current in a conductor, and its performance is described by the Peltier Coefficient, which is defined as the ratio of the generated heat current to the applied charge current1,2. To exploit the Peltier effect for thermoelectric cooling or heating, junctions of two conductors with different Peltier Coefficients have been believed to be indispensable. Here we challenge this conventional wisdom by demonstrating Peltier cooling and heating in a single material without junctions. This is realized through an anisotropic magneto-Peltier effect in which the Peltier Coefficient depends on the angle between the directions of a charge current and magnetization in a ferromagnet. By using active thermography techniques3–10, we observe the temperature change induced by this effect in a plain nickel slab. We find that the thermoelectric properties of the ferromagnet can be redesigned simply by changing the configurations of the charge current and magnetization, for instance, by shaping the ferromagnet so that the current must flow around a curve. Our experimental results demonstrate the suitability of nickel for the anisotropic magneto-Peltier effect and the importance of spin–orbit interaction in its mechanism. The anisotropic magneto-Peltier effect observed here is the missing thermoelectric phenomenon in ferromagnetic materials—the Onsager reciprocal of the anisotropic magneto-Seebeck effect previously observed in ferromagnets—and its simplicity might prove useful in developing thermal management technologies for electronic and spintronic devices. A ‘magneto-Peltier effect’ produces cooling or heating in a material without junctions, by forcing a change in angle between the current and magnetization in a single ferromagnetic nickel slab.
Fabio Taddei - One of the best experts on this subject based on the ideXlab platform.
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Thermoelectric properties of an interacting quantum dot based heat engine
2017Co-Authors: Paolo Andrea Erdman, Francesco Mazza, Riccardo Bosisio, Giuliano Benenti, Rosario Fazio, Fabio TaddeiAbstract:We study the thermoelectric properties and heat-to-work conversion performance of an interacting, multilevel quantum dot (QD) weakly coupled to electronic reservoirs. We focus on the sequential tunneling regime. The dynamics of the charge in the QD is studied by means of master equations for the probabilities of occupation. From here we compute the charge and heat currents in the linear response regime. Assuming a generic multiterminal setup, and for low temperatures (quantum limit), we obtain analytical expressions for the transport Coefficients which account for the interplay between interactions (charging energy) and level quantization. In the case of systems with two and three terminals we derive formulas for the power factor $Q$ and the figure of merit $ZT$ for a QD-based heat engine, identifying optimal working conditions which maximize output power and efficiency of heat-to-work conversion. Beyond the linear response we concentrate on the two-terminal setup. We first study the thermoelectric nonlinear Coefficients assessing the consequences of large temperature and voltage biases, focusing on the breakdown of the Onsager reciprocal relation between thermopower and Peltier Coefficient. We then investigate the conditions which optimize the performance of a heat engine, finding that in the quantum limit output power and efficiency at maximum power can almost be simultaneously maximized by choosing appropriate values of electrochemical potential and bias voltage. At last we study how energy level degeneracy can increase the output power.
Ron Jansen - One of the best experts on this subject based on the ideXlab platform.
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Spin heat accumulation induced by tunneling from a ferromagnet.
2014Co-Authors: Ivan J. Vera-marun, Van Bart Wees, Ron JansenAbstract:An electric current from a ferromagnet into a nonmagnetic material can induce a spin-dependent electron temperature. Here, it is shown that this spin heat accumulation, when created by tunneling from a ferromagnet, produces a non-negligible voltage signal that is comparable to that due to the coexisting electrical spin accumulation and can give a different Hanle spin precession signature. The effect is governed by the spin polarization of the Peltier Coefficient of the tunnel contact, its Seebeck Coefficient, and the spin heat resistance of the nonmagnetic material, which is related to the electrical spin resistance by a spin-Wiedemann-Franz law. Moreover, spin heat injection is subject to a heat conductivity mismatch that is overcome if the tunnel interface has a sufficiently large resistance.