The control of material interfaces at the atomic level has led to novel interfacial properties and functionalities. In particular, the study of polar discontinuities at interfaces between complex ...oxides lies at the frontier of modern condensed matter research. Here we employ a combination of experimental measurements and theoretical calculations to demonstrate the control of a bulk property, namely ferroelectric polarization, of a heteroepitaxial bilayer by precise atomic-scale interface engineering. More specifically, the control is achieved by exploiting the interfacial valence mismatch to influence the electrostatic potential step across the interface, which manifests itself as the biased-voltage in ferroelectric hysteresis loops and determines the ferroelectric state. A broad study of diverse systems comprising different ferroelectrics and conducting perovskite underlayers extends the generality of this phenomenon.
In conventional solid-state photovoltaics, electron-hole pairs are created by light absorption in a semiconductor and separated by the electric field spaning a micrometre-thick depletion region. The ...maximum voltage these devices can produce is equal to the semiconductor electronic bandgap. Here, we report the discovery of a fundamentally different mechanism for photovoltaic charge separation, which operates over a distance of 1-2 nm and produces voltages that are significantly higher than the bandgap. The separation happens at previously unobserved nanoscale steps of the electrostatic potential that naturally occur at ferroelectric domain walls in the complex oxide BiFeO(3). Electric-field control over domain structure allows the photovoltaic effect to be reversed in polarity or turned off. This new degree of control, and the high voltages produced, may find application in optoelectronic devices.
One of the outstanding challenges to information processing is the eloquent suppression of energy consumption in the execution of logic operations. The Landauer principle sets an energy constraint in ...deletion of a classical bit of information. Although some attempts have been made to experimentally approach the fundamental limit restricted by this principle, exploring the Landauer principle in a purely quantum mechanical fashion is still an open question. Employing a trapped ultracold ion, we experimentally demonstrate a quantum version of the Landauer principle, i.e., an equality associated with the energy cost of information erasure in conjunction with the entropy change of the associated quantized environment. Our experimental investigation substantiates an intimate link between information thermodynamics and quantum candidate systems for information processing.
A Strain-Driven Morphotropic Phase Boundary in BiFeO3 Zeches, R. J.; Rossell, M. D.; Zhang, J. X. ...
Science (American Association for the Advancement of Science),
11/2009, Letnik:
326, Številka:
5955
Journal Article
Recenzirano
Odprti dostop
Piezoelectric materials, which convert mechanical to electrical energy and vice versa, are typically characterized by the intimate coexistence of two phases across a morphotropic phase boundary. ...Electrically switching one to the other yields large electromechanical coupling coefficients. Driven by global environmental concerns, there is currently a strong push to discover practical lead-free piezoelectrics for device engineering. Using a combination of epitaxial growth techniques in conjunction with theoretical approaches, we show the formation of a morphotropic phase boundary through epitaxial constraint in lead-free piezoelectric bismuth ferrite (BiFeO3) films. Electric field–dependent studies show that a tetragonal-like phase can be reversibly converted into a rhombohedral-like phase, accompanied by measurable displacements of the surface, making this new lead-free system of interest for probe-based data storage and actuator applications.
Most nonequilibrium processes in thermodynamics are quantified only by inequalities; however, the Jarzynski relation presents a remarkably simple and general equality relating nonequilibrium ...quantities with the equilibrium free energy, and this equality holds in both the classical and quantum regimes. We report a single-spin test and confirmation of the Jarzynski relation in the quantum regime using a single ultracold ^{40}Ca^{+} ion trapped in a harmonic potential, based on a general information-theoretic equality for a temporal evolution of the system sandwiched between two projective measurements. By considering both initially pure and mixed states, respectively, we verify, in an exact and fundamental fashion, the nonequilibrium quantum thermodynamics relevant to the mutual information and Jarzynski equality.
The Heavy Ion Research Facility in Lanzhou (HIRFL) is a multi-disciplinary research facility that provides heavy ion beams for physical, biomedical and material sciences. It is a major academic ...facility of China and one of the world's important centers in nuclear physics and accelerators. The facility was built step by step at Institute of Modern Physics (IMP) over a half century. The first cyclotron was built with great assistance from the former Soviet Union in 1960s, and the newest linear accelerator was tested successfully in 2019. The HIRFL accelerator can provide beams from proton to Uranium with energies of hundreds MeV/u, and hence diverse fundamental sciences and applied researches were carried out at IMP. In this paper, an introduction of the HIRFL accelerator complex was presented. Details of the HIRFL components including ion sources, cyclotrons, synchrotrons, linac and experimental terminals were described. The current operation status and upgrade plans were reported.
The dynamic features of the low-intermediate-high-(L-I-H) confinement transitions on HL-2A tokamak are presented. Here we report the discovery of two types of limit cycles (dubbed type-Y and type-J), ...which show opposite temporal ordering between the radial electric field and turbulence intensity. In type-Y, which appears first after an L-I transition, the turbulence grows first, followed by the localized electric field. In contrast, the electric field leads type-J. The turbulence-induced zonal flow and pressure-gradient-induced drift play essential roles in the two types of limit cycles, respectively. The condition of transition between types-Y and -J is studied in terms of the normalized radial electric field. An I-H transition is demonstrated to occur only from type-J.
We show for the first time, with direct, multispacecraft calculations of electric current density, and other methods, matched signatures of field‐aligned currents (FACs) sampled simultaneously near ...the ionosphere at low (~500 km altitude) orbit and in the magnetosphere at medium (~2.5 RE altitude) orbits using a particular Swarm and Cluster conjunction. The Cluster signatures are interpreted and ordered through joint mapping of the ground/magnetospheric footprints and estimation of the auroral zone boundaries (taken as indication of the boundaries of Region 1 and Region 2 currents). We find clear evidence of both small‐scale and large‐scale FACs and clear matching of the behavior and structure of the large‐scale currents at both Cluster and Swarm. The methodology is made possible through the joint operations of Cluster and Swarm, which contain, in the first several months of Swarm operations, a number of close three‐spacecraft configurations.
Key Points
Gives correlated FAC signatures between low (~500 km) and high (~4 RE) altitudes
Resolves large‐ and small‐scale structures at low altitude
Confirms the scaling of current strength at each location
Objective
To determine the expression of circular RNA (circRNA) in blood corpuscles of pregnant women before 20 weeks of pregnancy and to create a new model to identify the performance of circRNA ...combined with protein factors for the early diagnosis of pre‐eclampsia (PE).
Design
Nested case–control study.
Setting
University medical centre, Guangzhou, China.
Population
A total of 1400 pregnant women recruited between 8 and 20 weeks of gestation. In all, 41 women with PE were included in the study, and were matched with 41 normally pregnant women based on maternal age and gestational age at same‐size ratio.
Methods
The samples were analysed using a human circRNA microarray in the discovery phase, then the circRNA and the plasma protein factor endoglin (ENG) were validated. Finally we combined ENG with circRNA to create a new early prediction model for PE.
Main outcome measures
Early changes of circRNA and ENG in PE.
Results
The circ_101222 levels in blood corpuscles of patients with PE were significantly higher than those in corresponding healthy women (P < 0.001). Using ENG in combination with circ_101222 resulted in a sensitivity of 0.7073, a specificity of 0.8049, and overall area under the curve of 0.876 (95% confidence interval 0.816–0.922) for the prediction of PE.
Conclusion
CircRNA and plasma proteins may have some predictive value for PE (such as circ_101222 and ENG). The performance of each of these factors may be strengthened when plasma proteins are used in combination with circRNA. The results are preliminary and need to be validated in larger studies and other populations.
Tweetable
Plasma protein endoglin in combination with circ_101222 strengthened the predictive power for pre‐eclampsia.
Tweetable
Plasma protein endoglin in combination with circ_101222 strengthened the predictive power for pre‐eclampsia.
Complex-oxide materials exhibit physical properties that involve the interplay of charge and spin degrees of freedom. However, an ambipolar oxide that is able to exhibit both electron-doped and ...hole-doped ferromagnetism in the same material has proved elusive. Here we report ambipolar ferromagnetism in LaMnO
, with electron-hole asymmetry of the ferromagnetic order. Starting from an undoped atomically thin LaMnO
film, we electrostatically dope the material with electrons or holes according to the polarity of a voltage applied across an ionic liquid gate. Magnetotransport characterization reveals that an increase of either electron-doping or hole-doping induced ferromagnetic order in this antiferromagnetic compound, and leads to an insulator-to-metal transition with colossal magnetoresistance showing electron-hole asymmetry. These findings are supported by density functional theory calculations, showing that strengthening of the inter-plane ferromagnetic exchange interaction is the origin of the ambipolar ferromagnetism. The result raises the prospect of exploiting ambipolar magnetic functionality in strongly correlated electron systems.
PDF
