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.

Optical Spectroscopic Study of the Interplay of Spin and Charge in NaV2O5

Abstract: Published in: Phys. Rev. B 61 (2000) 2535 Citing articles (CrossRef) citations recorded in [Science Citation Index] Abstract: We investigate the temperature dependent optical properties of NaV2O5, in the energy range 4meV-4eV. The symmetry of the system is discussed on the basis of infrared phonon spectra. By analyzing the optically allowed phonons at temperatures below and above the phase transition, we conclude that a second-order change to a larger unit cell takes place below 34 K, with a fluctuation regime extending over a broad temperature range. In the high temperature undistorted phase, we find good agreement with the recently proposed centrosymmetric space group Pmmn. On the other hand, the detailed analysis of the electronic excitations detected in the optical conductivity, provides direct evidence for a charge disproportionated electronic ground-state, at least on a locale scale: A consistent interpretation of both structural and optical conductivity data requires an asymmetrical charge distribution on each rung, without any long range order. We show that, because of the locally broken symmetry, spin-flip excitations carry a finite electric dipole moment, which is responsible for the detection of direct two-magnon optical absorption processes for E parallel to the a axis. The charged-magnon model, developed to interpret the optical conductivity of NaV2O5, is described in detail, and its relevance to other strongly correlated electron systems, where the interplay of spin and charge plays a crucial role in determining the low energy electrodynamics, is discussed.

Superconductivity in the Surface State of Noble Metal Gold and its Fermi Level Tuning by EuS Dielectric.

Abstract: The induced superconductivity (SC) in a robust and scalable quantum material with strong Rashba spin-orbit coupling is particularly attractive for generating topological superconductivity and Majorana bound states (MBS). Gold (111) thin film has been proposed as a promising candidate because of the large Rashba energy, the predicted topological nature, and the possibility for large-scale MBS device fabrications. We experimentally demonstrate two important steps towards achieving such a goal. We successfully show induced SC in the Shockley surface state (SS) of ultrathin Au(111) layers grown over epitaxial vanadium films, which is easily achievable on a wafer scale. The emergence of SC in the SS, which is physically separated from a bulk superconductor, is attained by indirect quasiparticle scattering processes instead of by conventional interfacial Andreev reflections. We further show the ability to tune the SS Fermi level (${E}_{F}$) by interfacing SS with a high-$\ensuremath{\kappa}$ dielectric ferromagnetic insulator EuS. The shift of ${E}_{F}$ from $\ensuremath{\sim}550$ to $\ensuremath{\sim}34\text{ }\text{ }\mathrm{mV}$ in superconducting SS is an important step towards realizing MBS in this robust system.

Coherent spin ratchets: A spin-orbit based quantum ratchet mechanism for spin-polarized currents in ballistic conductors

Abstract: We demonstrate that the combined effect of a spatially periodic potential, lateral confinement, and spin-orbit interaction gives rise to a quantum ratchet mechanism for spin-polarized currents in two-dimensional coherent conductors. Upon adiabatic ac driving, in the absence of a net static bias, the system generates a directed spin current while the total charge current is zero. We analyze the underlying mechanism by employing symmetry properties of the scattering matrix and numerically verify the effect for different setups of ballistic conductors. The spin current direction can be changed upon tuning the Fermi energy or the strength of the Rashba spin-orbit coupling.

A molecular-dynamics study of (b2o3)1-x-y(li2o)x(li2cl2)y and (b2o3)1-x-y(li2o)x(cs2o)y

Abstract: The structures of borate glasses with various contents of Li 2 O, LiCl and Cs 2 O have been simulated by use of molecular dynamics. Calculated radial distribution functions are in agreement with X-ray diffraction studies. The structure of v-B 2 O 3 consists of randomly linked BO 3 triangles. Addition of Li 2 O invokes a change of BO 3 triangles into BO 4 tetrahedrals. Addition of liCl leads to a more open boron-oxygen glass network and consequently to a decrease of the boron coordination number. Velocity autocorrelation functions, Raman and infrared spectra have been calculated and compared with experimental spectra. The frequency spectra of the Li and Cs atoms are in agreement with far IR measurements. The dominant parts of the overall vibrational density of states (DOS) spectra are due to nearest neighbor B-O stretching modes. The calculated IR spectra show one main peak, with a maximum at about 1100 cm −1 . This maximum shifts towards lower frequencies upon addition of alkali oxide, but no significant changes are observed if LiCl is added. These results are in agreement with experiment. For the calculation of the Raman spectra, only autocorrelated B-O bonds were taken into account. These calculations fail to reproduce the dominant experimental bands at 780 and 800 cm −1 . For a proper calculation of the Raman spectra of borate glasses, apparently cross-correlated B-O bond stretching vibrations should be taken into account.