Solid State Physics Laboratory

About: Solid State Physics Laboratory is a facility organization based out in Delhi, India. It is known for research contribution in the topics: Quantum dot & Dielectric. The organization has 1754 authors who have published 2597 publications receiving 50601 citations.

Electron transport and thermoelectric properties of layered perovskite LaBaCo(2)O(5.5).

Abstract: We have investigated systematically the physical transport properties of layered 112-type cobaltite by means of electrical resistivity, magnetoresistance and thermopower measurements In order to understand the complex transport mechanism of LaBaCo2O55, the data have been analysed using different theoretical models The compound shows an electronic transition between two semiconducting states around 326 K, which coincides with the ferromagnetic transition Interestingly, the system also depicts a significant magnetoresistance (MR) effect near the ferro/antiferromagnetic phase boundary and the highest value of MR is close to 5% at 245 K under ± 7 T The temperature dependence of thermopower, S(T), exhibits p-type conductivity in the 60 K≤T≤320 K range and reaches a maximum value of around 303 µV K−1 (at 120 K) In the low temperature antiferromagnetic region the unusual S(T) behaviour, generally observed for the cobaltite series LnBaCo2O55 (Ln = rare earth), is explained by the electron magnon scattering mechanism

Ionization of Interstitial Iron Atoms in β-Rhombohedral Boron

Abstract: Mossbauer spectra of β-rhombohedral boron with interstitially distributed iron atoms up to 3.33 at% are presented. Taking into account that the six D sites in the unit cell are saturated by two Fe atoms, the distribution of the Fe atoms on A and D sites proved to be simply statistical. At lower Fe contents single iron atoms on A sites are ionized to Fe3+, while towards higher Fe contents a rapidly increasing share of Fe2+ ions is found. On D sites the ionization of single Fe atoms is 2+, but it changes to 3+, when two Fe atoms are accommodated in the D sites of one unit cell. The isomer shift of the Mossbauer doublets yields an estimation of the electron transfer to the boron framework. Transition from p- to n-type takes place, when six electrons per unit cell are transferred from the iron ions to the boron framework. This number corresponds to the sum of the unoccupied sites in the upper valence band and the possible electron traps generated by an electron–phonon interaction in the B12 icosahedra. Mosbauerspektren von β-rhomboedrischem Bor mit Eisenatomen auf Zwischengitterplatzen bis zu Konzentrationen von etwa 3,33 at% werden gemessen. Berucksichtigt man, das die sechs D-Positionen in der Elementarzelle bereits mit zwei Eisenatomen abgesattigt sind, erweisen sich die Verteilungen auf die Zwischengitterplatze als statistisch. Bei kleiner Fe-Konzentration findet man nur Fe3+−Ionen auf A-Platzen, wahrend zu hoherer Konzentration hin ein stark zunehmender Anteil von Fe2+−Ionen auftritt. Einzelatome auf D-Platzen sind zweifach, Paare jedoch dreifach ionisiert. Aus der Isomerieverschiebung der Mosbauerdubletten last sich der Elektronenubergang auf die Borstruktur abschatzen; der ubergang von p- zur n-Leitung erfordert sechs Elektronen pro Elementarzelle. Diese Zahl entspricht der Summe aus unbesetzten Platzen im Valenzbandbereich und moglichen Elektronenhaftstellen, welche durch Elektron–Phonon-Wechselwirkung in den B12-Ikosaedern gebildet werden.

Spin-Orbit Coupling at the Level of a Single Electron.

Abstract: We utilize electron counting techniques to distinguish a spin-conserving fast tunneling process and a slower process involving spin flips in AlGaAs/GaAs-based double quantum dots. By studying the dependence of the rates on the interdot tunnel coupling of the two dots, we find that as many as 4% of the tunneling events occur with a spin flip related to spin-orbit coupling in GaAs. Our measurement has a fidelity of 99% in terms of resolving whether a tunneling event occurred with a spin flip or not.