There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Redox‐Based Resistive Switching Memories – Nanoionic Mechanisms, Prospects, and Challenges

Polarity discontinuities at the interfaces between different crystalline materials (heterointerfaces) can lead to nontrivial local atomic and electronic structure, owing to the presence of dangling bonds and incomplete atomic coordinations. These discontinuities often arise in naturally layered oxide structures, such as the superconducting copper oxides and ferroelectric titanates, as well as in artificial thin film oxide heterostructures such as manganite tunnel junctions. If polarity discontinuities can be atomically controlled, unusual charge states that are inaccessible in bulk materials could be realized. Here we have examined a model interface between two insulating perovskite oxides--LaAlO3 and SrTiO3--in which we control the termination layer at the interface on an atomic scale. In the simple ionic limit, this interface presents an extra half electron or hole per two-dimensional unit cell, depending on the structure of the interface. The hole-doped interface is found to be insulating, whereas the electron-doped interface is conducting, with extremely high carrier mobility exceeding 10,000 cm2 V(-1) s(-1). At low temperature, dramatic magnetoresistance oscillations periodic with the inverse magnetic field are observed, indicating quantum transport. These results present a broad opportunity to tailor low-dimensional charge states by atomically engineered oxide heteroepitaxy.

A high-mobility electron gas at the LaAlO3/SrTiO3 heterointerface

Nanocrystals (NCs) discussed in this Review are tiny crystals of metals, semiconductors, and magnetic material consisting of hundreds to a few thousand atoms each. Their size ranges from 2-3 to about 20 nm. What is special about this size regime that placed NCs among the hottest research topics of the last decades? The quantum mechanical coupling * To whom correspondence should be addressed. E-mail: dvtalapin@uchicago.edu. † The University of Chicago. ‡ Argonne National Lab. Chem. Rev. 2010, 110, 389–458 389

/pdf/prospects-of-colloidal-nanocrystals-for-electronic-and-3dxpyhl3r7.pdf

Prospects of Colloidal Nanocrystals for Electronic and Optoelectronic Applications

Etude du spectre de transmission de fumees d'argent dans un milieu de KBr, entre 400 et 50000 cm −1 . Comparaison du resultat experimental aux predictions de modeles theoriques comme la theorie de Maxwell Garnett et la theorie de Mic. Pour des particules assez grosses (ā=1250 A), la theorie de Mie donne le meilleur accord avec l'experience

Effect of an oxide coating on the infrared and visible absorption of small silver particles.

The temperature dependence of the far-infrared absorption coefficient for an unoxidized silver-particle--Teflon composite is reported. Large enhancement of the absorption coefficient over the prediction of the simple Maxwell-Garnett theory is observed and explained by the Curtin-Ashcroft theory for a highly metallic cluster [Phys. Rev. B 31, 3287 (1985)]. After modifying the relaxation time of the electrons in the model, we can also explain the temperature dependence.

Temperature-dependent far-infrared absorption of a metal-insulator composite

We investigated domain nucleation process in epitaxial Pb(Zr,Ti)O3 capacitors under a modified piezoresponse force microscope. We obtained domain evolution images during polarization switching process and observed that domain nucleation occurs at particular sites. This inhomogeneous nucleation process should play an important role in an early stage of switching and under a high electric field. We found that the number of nuclei is linearly proportional to log(switching time), suggesting a broad distribution of activation energies for nucleation. The nucleation sites for a positive bias differ from those for a negative bias, indicating that most nucleation sites are located at ferroelectric/electrode interfaces.

Observation of inhomogeneous domain nucleation in epitaxial Pb(Zr,Ti)O3 capacitors

A new experimental approach to two-dimensional percolation

Dimensionality control in the LaNiO3 (LNO) heterostructure has attracted attention due to its two-dimensional (2D) electronic structure was predicted to have an orbital ordered insulating ground state, analogous to that of the parent compound of high-Tc cuprate superconductors [P. Hansmann et al., Phys. Rev. Lett. 103, 016401 (2009)]. Here, we directly measured the electronic structure of LNO ultrathin films using in situ angle-resolved photoemission spectroscopy (ARPES). We recognized the dimensional crossover of the electronic structure around 3-unit cells (UC)-thick LNO film and observed the orbital reconstruction. However, complete orbital ordering was not achieved. Instead, we observed that the Fermi surface nesting effect became strong in the 2D LNO ultrathin film. These results indicated that the orbital reconstruction should be described by taking into account the strong nesting effect to search for the novel phenomena, such as superconductivity in 2D LNO heterostructure. In addition, the APRES spectra showed that the Fermi surface existed down to a 1-UC-thick film, which showed insulating behavior in transport measurements. We suggested that the metal-insulator transition in the transport properties may originate from Anderson localization.

Dimensional crossover of the electronic structure in LaNiO3 ultrathin films: Orbital reconstruction, Fermi surface nesting, and the origin of the metal-insulator transition

Tae Won Noh

Papers

Effect of an oxide coating on the infrared and visible absorption of small silver particles.

Temperature-dependent far-infrared absorption of a metal-insulator composite

Observation of inhomogeneous domain nucleation in epitaxial Pb(Zr,Ti)O3 capacitors

A new experimental approach to two-dimensional percolation

Dimensional crossover of the electronic structure in LaNiO3 ultrathin films: Orbital reconstruction, Fermi surface nesting, and the origin of the metal-insulator transition