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.

Fishtail effect in neutron-irradiated superconducting MgB 2 single crystals

Abstract: We report on the effects of neutron irradiation in superconducting ${\mathrm{MgB}}_{2}$ single crystals. Transmission electron microscopy investigations reveal large radiation-induced defects with dimensions comparable to the superconducting coherence length. Accordingly, measurements of the magnetic moment show pronounced modifications of the reversible and irreversible properties after irradiation. In particular, we concentrate on the emergence of a second peak (fishtail), situated near ${H}_{c2}$ at low neutron fluences, but extending over a large part of the superconducting phase diagram at high doses. The history dependence of the critical current density on the low-field side of the fishtail region is studied by measuring minor hysteresis loops and interpreted in terms of an order-disorder transition of the vortex lattice.

Electronic structure and chemical reactivity of oxide-metal interfaces: MgO(100)/Ag(100)

Abstract: We present an electron spectroscopy investigation of the MgO(100)/Ag(100) oxide-metal interface electronic structure. We find that the O $2p$ states strongly hybridize with the Ag $5sp$ band and only weakly with the Ag $4d$ band. As a result of these interactions, a substantial density of states with a large oxygen antibonding character is pushed above the Fermi level, determining the chemical bonding at the oxide-metal interface. One striking consequence of such an electronic structure is the strong chemical activity of the interface toward ${\mathrm{H}}_{2}\mathrm{O}$ dissociative chemisorption.

Plasmon hybridization in pyramidal metamaterials: a route towards ultra-broadband absorption

Abstract: Pyramidal metamaterials are currently developed for ultra-broadband absorbers. They consist of periodic arrays of alternating metal/dielectric layers forming truncated square-based pyramids. The metallic layers of increasing lengths play the role of vertically and, to a less extent, laterally coupled plasmonic resonators. Based on detailed numerical simulations, we demonstrate that plasmon hybridization between such resonators helps in achieving ultra-broadband absorption. The dipolar modes of individual resonators are shown to be prominent in the electromagnetic coupling mechanism. Lateral coupling between adjacent pyramids and vertical coupling between alternating layers are proven to be key parameters for tuning of plasmon hybridization. Following optimization, the operational bandwidth of Au/Ge pyramids, i.e. the bandwidth within which absorption is higher than 90%, extends over a 0.2-5.8 µm wavelength range, i.e. from UV-visible to mid-infrared, and total absorption (integrated over the operational bandwidth) amounts to 98.0%. The omni-directional and polarization-independent high-absorption properties of the device are verified. Moreover, we show that the choice of the dielectric layer material (Si versus Ge) is not critical for achieving ultra-broadband characteristics, which confers versatility for both design and fabrication. Realistic fabrication scenarios are briefly discussed. This plasmon hybridization route could be useful in developing photothermal devices, thermal emitters or shielding devices that dissimulate objects from near infrared detectors.

Absolute negative conductivity in two-dimensional electron systems associated with acoustic scattering stimulated by microwave radiation

Abstract: We discuss the feasibility of absolute negative conductivity (ANC) in two-dimensional electron systems (2DES's) stimulated by microwave radiation in a transverse magnetic field. The mechanism of ANC under consideration is associated with electron scattering on acoustic phonons accompanied by absorption of microwave photons. It is demonstrated that the dissipative components of the 2DES dc conductivity can be negative $({\ensuremath{\sigma}}_{\mathrm{xx}}={\ensuremath{\sigma}}_{\mathrm{yy}}l0)$ due to negative values of the dc photoconductivity caused by microwave radiation at certain ratios of the microwave frequency $\ensuremath{\Omega}$ and the electron cyclotron frequency ${\ensuremath{\Omega}}_{c}.$ The phase of the oscillations of the dissipative dc photoconductivity associated with photon-assisted electron scattering on acoustic phonons is quite different from that in the case of the photon-assisted impurity scattering mechanism. The concept of ANC associated with an interplay of the scattering mechanisms can be invoked to explain the nature of the occurrence of zero-resistance ``dissipationless'' states observed in recent experiments.