Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 8 of 8
Full-Text Articles in Physics
Ferroelectric Instability Under Screened Coulomb Interactions, Yong Wang, Xiaohui Liu, John D. Burton, Sitaram S. Jaswal, Evgeny Y. Tsymbal
Ferroelectric Instability Under Screened Coulomb Interactions, Yong Wang, Xiaohui Liu, John D. Burton, Sitaram S. Jaswal, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
We explore the effect of charge carrier doping on ferroelectricity using density functional calculations and phenomenological modeling. By considering a prototypical ferroelectric material, BaTiO3, we demonstrate that ferroelectric displacements are sustained up to the critical concentration of 0.11 electron per unit cell volume. This result is consistent with experimental observations and reveals that the ferroelectric phase and conductivity can coexist. Our investigations show that the ferroelectric instability requires only a short-range portion of the Coulomb force with an interaction range of the order of the lattice constant. These results provide a new insight into the origin of ferroelectricity …
New View Of The Occupied Band Structure Of Mo(112), Keisuke Fukutani, Hirokazu Hayashi, I. N. Yakovkin, Tula R. Paudel, Takafumi Habuchi, Daisuke Hirayama, Jian Jiang, Hideaki Iwasawa, Kenya Shimada, Ning Wu, Evgeny Y. Tsymbal, Yaroslav B. Losovyj, Peter A. Dowben
New View Of The Occupied Band Structure Of Mo(112), Keisuke Fukutani, Hirokazu Hayashi, I. N. Yakovkin, Tula R. Paudel, Takafumi Habuchi, Daisuke Hirayama, Jian Jiang, Hideaki Iwasawa, Kenya Shimada, Ning Wu, Evgeny Y. Tsymbal, Yaroslav B. Losovyj, Peter A. Dowben
Evgeny Tsymbal Publications
We present a comprehensive examination of the occupied surface-weighted band structure of Mo(112) along the two high-symmetry directions of the surface Brillouin zone, both from theoretical and experimental perspectives. The band structures are found to be significantly different for the states along the two high-symmetry directions and for the states with even and odd reflection parities with respect to the mirror planes. The present study suggests the existence of a number of surface-weighted bands along both high-symmetry directions. The complexity of the band structure near the Fermi level may impose potential difficulties in experimental determination of the electronphonon coupling parameters …
Ferroelectric And Multiferroic Tunnel Junctions, Evgeny Y. Tsymbal, Alexei Gruverman, Vincent Garcia, Manuel Bibes, A. Barthélémy
Ferroelectric And Multiferroic Tunnel Junctions, Evgeny Y. Tsymbal, Alexei Gruverman, Vincent Garcia, Manuel Bibes, A. Barthélémy
Evgeny Tsymbal Publications
The phenomenon of electron tunneling has been known since the advent of quantum mechanics, but continues to enrich our understanding of many fi elds of physics, as well as creating sub-fi elds on its own. Spin-dependent tunneling in magnetic tunnel junctions has aroused considerable interest and development. In parallel with this endeavor, recent advances in thin-fi lm ferroelectrics have demonstrated the possibility of achieving stable and switchable ferroelectric polarization in nanometer-thick fi lms. This discovery opened the possibility of using thin-fi lm ferroelectrics as barriers in magnetic tunnel junctions, thus merging the fi elds of magnetism, ferroelectricity, and spin-polarized transport …
Intrinsic Defects In Multiferroic Bifeo3 And Their Effect On Magnetism, Tula R. Paudel, Sitaram S. Jaswal, Evgeny Y. Tsymbal
Intrinsic Defects In Multiferroic Bifeo3 And Their Effect On Magnetism, Tula R. Paudel, Sitaram S. Jaswal, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
We investigate the energetics of the intrinsic defects in bulk multiferroic BiFeO3 and explore their implication for magnetization using a first-principles approach based on density functional theory. We find that the dominant defects in oxidizing (oxygen-rich) conditions are Bi and Fe vacancies and in reducing (oxygen-poor) conditions are O and Bi vacancies. The calculated carrier concentration shows that the BiFeO3 grown in oxidizing conditions has p-type conductivity. The conductivity decreases with oxygen partial pressure, and the material becomes insulating with a tendency for n-type conductivity. We find that the Bi and Fe vacancies produce a magnetic …
Magnetic And Superconducting Phases At The Laalo3/Srtio3 Interface: The Role Of Interfacial Ti 3D Electrons, N. Pavlenko, Thilo Kopp, Evgeny Y. Tsymbal, George A. Sawatzky, Jochen Mannhart
Magnetic And Superconducting Phases At The Laalo3/Srtio3 Interface: The Role Of Interfacial Ti 3D Electrons, N. Pavlenko, Thilo Kopp, Evgeny Y. Tsymbal, George A. Sawatzky, Jochen Mannhart
Evgeny Tsymbal Publications
Ferromagnetism and superconductivity are, in most cases, adverse. However, recent experiments reveal that they coexist at interfaces of LaAlO3 and SrTiO3. We analyze the magnetic state within density functional theory and provide evidence that magnetism is not an intrinsic property of the two-dimensional electron liquid at the interface. We demonstrate that the robust ferromagnetic state is induced by the oxygen vacancies in SrTiO3 or in the LaAlO3 layer. This allows for the notion that areas with increased density of oxygen vacancies produce ferromagnetic puddles and account for the previous observation of a superparamagnetic behavior in …
Coherent Potential Approximation As A Voltage Probe, Mikhail Ye Zhuravlev, A. V. Vedyayev, Kirill D. Belashchenko, Evgeny Y. Tsymbal
Coherent Potential Approximation As A Voltage Probe, Mikhail Ye Zhuravlev, A. V. Vedyayev, Kirill D. Belashchenko, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
Coherent potential approximation (CPA) haswidely been used for studying the residual resistivity of bulk alloys and electrical conductivity in systems with structural disorder. Here, we revisit the single-site CPA within the Landauer-Büttiker approach applied to the electronic transport in layered structures and show that thismethod can be interpreted in terms of the B¨uttiker voltage-probe model that has been developed for treating phase-breaking scattering in mesoscopic systems. We demonstrate that the on-site vertex function, which appears within the single-site CPA formalism, plays the role of the local chemical potential within the voltage-probe approach. This interpretation allows the determination of the chemical …
Multiferroic Tunnel Junctions With Poly(Vinylidene Fluoride), Julian P. Velev, Juan M. López-Encarnación, John D. Burton, Evgeny Y. Tsymbal
Multiferroic Tunnel Junctions With Poly(Vinylidene Fluoride), Julian P. Velev, Juan M. López-Encarnación, John D. Burton, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
We perform first-principles calculations based on density functional theory of the spin-resolved conductance of poly(vinylidene fluoride)- (PVDF) based multiferroic tunnel junctions (MFTJs).We consider Co/PVDF/O/Co (0001) MFTJs with one oxidized interface, representing the different experimental growth conditions for the two interfaces. We demonstrate that this natural asymmetry leads to multiple resistance states associated with different magnetization configurations of the electrodes and ferroelectric polarization orientations of the barrier. Our results indicate very high tunability of the tunneling magnetoresistance and electroresistance effects, which could be useful for logic and memory applications.
Interface Dipole Effect On Thin Film Ferroelectric Stability: First-Principles And Phenomenological Modeling, Xiaohui Liu, Yong Wang, Pavel V. Lukashev, John D. Burton, Evgeny Y. Tsymbal
Interface Dipole Effect On Thin Film Ferroelectric Stability: First-Principles And Phenomenological Modeling, Xiaohui Liu, Yong Wang, Pavel V. Lukashev, John D. Burton, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
Utilization of the switchable spontaneous polarization of ferroelectric materials offers a promising avenue for the future of nanoelectronic memories and logic devices provided that nanoscale metal-ferroelectric-metal heterostructures can be engineered to maintain a bi-stable polarization switchable by an applied electric field. The most challenging aspect of this approach is to overcome the deleterious interface effects which tend to render ferroelectric polarization either unstable or unswitchable and which become ever more important as ferroelectric materials are produced thinner and thinner. Here we use first-principles density functional calculations and phenomenological modeling to demonstrate that a BaO/RuO2 interface termination sequence in SrRuO …