Yuanhua Zheng
Ohio State University
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by Yuanhua Zheng.
Physical Review B | 2016
Sarah J. Watzman; R. A. Duine; Yaroslav Tserkovnyak; Stephen R. Boona; Hyungyu Jin; Arati Prakash; Yuanhua Zheng; Joseph P. Heremans
Magnon drag is shown to dominate the thermopower of elemental Fe from 2 to 80 K and of elemental Co from 150 to 600 K; it is also shown to contribute to the thermopower of elemental Ni from 50 to 500 K. Two theoretical models are presented for magnon-drag thermopower. One is a hydrodynamic theory based purely on nonrelativistic, Galilean, spin-preserving electron-magnon scattering. The second is based on spin-motive forces, where the thermopower results from the electric current pumped by the dynamic magnetization associated with a magnon heat flux. In spite of their very different microscopic origins, the two give similar predictions for pure metals at low temperature, allowing us to semiquantitatively explain the observed thermopower of elemental Fe and Co without adjustable parameters. We also find that magnon drag may contribute to the thermopower of Ni. A spin-mixing model is presented that describes the magnon-drag contribution to the anomalous Nernst effect in Fe, again enabling a semiquantitative match to the experimental data without fitting parameters. Our paper suggests that particle nonconserving processes may play an important role in other types of drag phenomena and also gives a predicative theory for improving metals as thermoelectric materials.
Applied Physics Letters | 2018
Yuewei Zhang; Adam T. Neal; Zhanbo Xia; Chandan Joishi; Jared M. Johnson; Yuanhua Zheng; Sanyam Bajaj; Mark Brenner; Donald L. Dorsey; Kelson D. Chabak; Gregg H. Jessen; Jinwoo Hwang; Shin Mou; Joseph P. Heremans; Siddharth Rajan
In this work, we demonstrate a high mobility two-dimensional electron gas (2DEG) formed at the β-(AlxGa1-x)2O3/Ga2O3 interface through modulation doping. Shubnikov-de Haas (SdH) oscillations were observed in the modulation-doped β-(AlxGa1-x)2O3/Ga2O3 structure, indicating a high-quality electron channel formed at the heterojunction interface. The formation of the 2DEG channel was further confirmed by the weak temperature dependence of the carrier density, and the peak low temperature mobility was found to be 2790 cm2/Vs, which is significantly higher than that achieved in bulk-doped Beta-phase Gallium Oxide (β-Ga2O3). The observed SdH oscillations allowed for the extraction of the electron effective mass in the (010) plane to be 0.313 ± 0.015 m0 and the quantum scattering time to be 0.33 ps at 3.5 K. The demonstrated modulation-doped β-(AlxGa1-x)2O3/Ga2O3 structure lays the foundation for future exploration of quantum physical phenomena and semiconductor device technologies based on the β-Ga2O3 material s...
Proceedings of SPIE | 2016
Joseph P. Heremans; Hyungyu Jin; Yuanhua Zheng; Sarah J. Watzman; Arati Prakash
This article reviews the factors limiting the figure of merit zT of conventional thermoelectrics especially at cryogenic temperatures and then highlights modern approaches used to increase zT below 200 K. Two type of materials are discussed. The first are BiSb alloys, relatively conventional thermoelectrics in which the zT is enhanced by using resonant levels. The second is the spin- Seebeck effect (SSE), a new solid-state energy conversion technology. Classical thermoelectric and SSE physics are combined to provide new concepts, like magnon-drag, in which we hope to increase the performance of solid-state coolers by exploiting the spin degree of freedom.
AIP Advances | 2017
Zihao Yang; Emilio Codecido; Jason Marquez; Yuanhua Zheng; Joseph P. Heremans; Roberto C. Myers
The Nernst thermopower usually is considered far too weak in most metals for waste heat recovery. However, its transverse orientation gives it an advantage over the Seebeck effect on non-flat surfaces. Here, we experimentally demonstrate the scalable generation of a Nernst voltage in an air-cooled metal wire coiled around a hot cylinder. In this geometry, a radial temperature gradient generates an azimuthal electric field in the coil. A Galfenol (Fe
Materials Today Physics | 2017
Koen Vandaele; Sarah J. Watzman; Benedetta Flebus; Arati Prakash; Yuanhua Zheng; Stephen R. Boona; Joseph P. Heremans
_{0.85}
arXiv: Materials Science | 2018
Yuewei Zhang; Adam T. Neal; Zhanbo Xia; Chandan Joishi; Yuanhua Zheng; Sanyam Bajaj; Mark Brenner; Shin Mou; Donald L. Dorsey; Kelson D. Chabak; Gregg H. Jessen; Jinwoo Hwang; Joseph P. Heremans; Siddharth Rajan
Ga
Bulletin of the American Physical Society | 2018
Yuanhua Zheng; Tianqi Lu; Morteza Rasoulianboroujeni; Huaizhou Zhao; Daryoosh Vashaee; Joseph P. Heremans
_{0.15}
Bulletin of the American Physical Society | 2018
Mike Adams; Yuanhua Zheng; Joseph P. Heremans
) wire is wrapped around a cartridge heater, and the voltage drop across the wire is measured as a function of axial magnetic field. As expected, the Nernst voltage scales linearly with the length of the wire. Based on heat conduction and fluid dynamic equations, finite-element method is used to calculate the temperature gradient across the Galfenol wire and determine the Nernst coefficient. A giant Nernst coefficient of -2.6
Bulletin of the American Physical Society | 2017
Emilio Codecido; Zihao Yang; Jason Marquez; Yuanhua Zheng; Joseph P. Heremans; Roberto C. Myers
{\mu}
Bulletin of the American Physical Society | 2017
Yuanhua Zheng; Mike Adams; Nicolas Antolin; Wolfgang Windl; Joseph P. Heremans
V/KT at room temperature is estimated, in agreement with measurements on bulk Galfenol. We expect that the giant Nernst effect in Galfenol arises from its magnetostriction, presumably through enhanced magnon-phonon coupling. Our results demonstrate the feasibility of a transverse thermoelectric generator capable of scalable output power from non-flat heat sources.