FeSe is the focus of intense research interest because of its unusual non-magnetic nematic state and because it forms the basis for achieving the highest critical temperatures of any iron-based superconductor. However, its Cooper pairing mechanism has not been determined because an accurate knowledge of the momentum-space structure of superconducting energy gaps ∆ i ( k) on the different electron-bands E i ( k) does not exist. Here we use Bogoliubov quasiparticle interference (BQPI) imaging to determine the coherent Fermi surface geometry of the α-and ε-bands surrounding the Γ = (0, 0) and X = (π/a Fe , 0) points of FeSe, and to measure their superconducting energy gaps ∆ α ( k) and ∆ ε ( k).We show directly that both gaps are extremely anisotropic but nodeless, and are aligned along orthogonal crystal axes. Moreover, by implementing a novel technique we demonstrate the sign change between ∆ α ( k) and ∆ ε ( k). This complex configuration of ∆ α ( k) and ∆ ε ( k), which was unanticipated within pairing theories for FeSe, reveals a unique form of superconductivity based on orbital selective Cooper pairing of electrons from the d yz orbitals of iron atoms. This new paradigm of orbital selectivity may be pivotal to understanding the microscopic interplay of quantum paramagnetism, nematicity and high temperature superconductivity. BIOGRAPHICAL SKETCHPeter Oliver Sprau was born on June 13th 1986 in the small town of Kirchheimbolanden, Germany, where he completed both his primary and secondary education. Long before he was a physicist, Peter was an active member of the track and field team in his school and a local club, even going on to compete in the dash and relay event on the state and federal youth level. Upon finishing school, he fulfilled his civic duty and carried out his alternative civilian service in the hospital in Kirchheimbolanden. While Peter's academic interests were diverse, including not just science but also Latin and history, his natural curiosity about the world finally urged him to pursue a higher education in physics. Mistakes. Make glorious, amazing mistakes. Make mistakes nobody's ever made before. Don't freeze, don't stop, don't worry that it isn't good enough, or it isn't perfect, whatever it is: art, or love, or work or family or life.Whatever it is you're scared of doing, Do it. Make your mistakes, next year and forever." I also want to acknowledge in no specific order the following people for useful discussions throughout my PhD:

We provide a band structure with low-energy properties consistent with recent photoemission and quantum oscillations measurements on FeSe, assuming mean-field like s and/or d-wave orbital ordering at the structural transition. We show how the resulting model provides a consistent explanation of the temperature dependence of the measured Knight shift and the spin-relaxation rate. Furthermore, the superconducting gap structure obtained from spin fluctuation theory exhibits nodes on the electron pockets, consistent with the 'V'-shaped density of states obtained by tunneling spectroscopy on this material, and the temperature dependence of the London penetration depth. Our studies prove that the recent experimental observations of the electronic properties of FeSe are consistent with orbital order, but leave open the microscopic origin of the unusual band structure of this material.

We present a theoretical study of the dynamical spin susceptibility for the intriguing Fe-based superconductor FeSe, based on a tight-binding model developed to account for the temperaturedependent band structure in this system. The model allows for orbital ordering in the dxz/dyz channel below the structural transition and presents a strongly C4 symmetry broken Fermi surface at low temperatures which accounts for the nematic properties of this material. The calculated spin excitations are peaked at wave vector (π, 0) in the 1-Fe Brillouin zone, with a broad maximum at energies of order a few meV. In this range, the occurrence of superconductivity sharpens this peak in energy, creating a (π, 0) "neutron resonance" as seen in recent experiments. With the exception of the quite low energy scale of these fluctuations, these results are roughly similar to standard behavior in Fe pnictide systems. At higher energies, however, intensity increases and shifts to wave vectors along the (π, 0) -(π, π) line. We compare with existing inelastic neutron experiments and NMR data, and give predictions for further studies.

We present evidence of strain-induced modulation of electron correlation effects and increased orbital anisotropy in the rutile phase of epitaxial VO2/TiO2 films from hard x-ray photoelectron spectroscopy and soft V L-edge x-ray absorption spectroscopy, respectively. By using the U(1) slave spin formalism, we further argue that the observed anisotropic correlation effects can be understood by a model of orbital selective Mott transition at a filling that is non-integer, but close to the halffilling. Because the overlaps of wave functions between d orbitals are modified by the strain, orbitaldependent renormalizations of the bandwidths and the on-site energy occur. These renormalizations generally result in different occupation numbers in different orbitals. We find that if the system has a non-integer filling number near the half-filling such as for VO2, certain orbitals could reach an occupation number closer to half-filling under the strain, resulting in a strong reduction in the quasiparticle weight Zα of that orbital. Our work demonstrates that such an orbital selective Mott transition, defined as the case with Zα = 0 in some, but not all orbitals, could be accessed by epitaxial-strain engineering of correlated electron systems.*These authors contributed equally.

Atomically thin topological materials are attracting growing attention for their potential to radically transform classical and quantum electronic device concepts. Among them is the quantum spin Hall (QSH) insulator—a 2D state of matter that arises from interplay of topological band inversion and strong spin–orbit coupling, with large tunable bulk bandgaps up to 800 meV and gapless, 1D edge states. Reviewing recent advances in materials science and engineering alongside theoretical description, the QSH materials library is surveyed with focus on the prospects for QSH‐based device applications. In particular, theoretical predictions of nontrivial superconducting pairing in the QSH state toward Majorana‐based topological quantum computing are discussed, which are the next frontier in QSH materials research.

We report the discovery of ferroelectricity below 4.5 K in highly underdoped La 2 CuO 4+x accompanied by slow charge dynamics which develop below T~40 K. An anisotropic magnetoelectric response has also been observed, indicating considerable spin-charge coupling in this lightly doped "parent" high temperature copper-oxide superconductor. The ferroelectric state is proposed to develop from polar nanoregions, in which spatial inversion symmetry is locally broken due to non-stoichiometric carrier doping.

IntroductionDental infections are multimicrobial in origin with their etiological factors involving a combination of Gram-positive, Gram-negative, facultative anaerobes, and obligate anaerobic bacteria. Thus, antibiotics and analgesics account for a great majority of medicines prescribed by the dental surgeons. Inappropriate prescription of antibiotics by health care professionals has become a worldwide issue nowadays.AimThe purpose of the present study was to:• Determine the pattern of antibiotic prescription among dentists of Kolkata.• Assess the attitude of dentists toward antibiotic resistance.Materials and methodsAn electronic version of the questionnaire of cross-sectional survey regarding antibiotic use and attitude toward growing antibiotic resistance was constructed using Qualtrics (Qualtrics Pvt. Limited Provo, Utah), an internet online survey tool that was e-mailed to dental surgeons of Kolkata registered with Indian Dental Association (IDA), West Bengal. A reminder e-mail was given after 1 month to recollect the responses from them.ResultsThe survey was e-mailed to 300 dental surgeons, out of which 115 dental surgeons completed the survey, thereby achieving a response rate of 38.33%. Majority of the respondents (60%) chose amoxicillin in nonallergic patients. Average minimum duration of antibiotic therapy was 5 days. The drug of first choice for patients with an allergy to penicillin was erythromycin. The prime determinant of antibiotic use was facial swelling (68%). The prime determinant to select a particular brand of antibiotics was affordability of that brand (61%). Almost all (99%) dental surgeons were aware of antibiotic resistance being a growing concern. As per their views, there was overprescription of antibiotics.How to cite this article: Kaul R, Angrish P, Jain P, Saha S, Sengupta AV, Mukherjee S. A Survey on the Use of Antibiotics among the Dentists of Kolkata, West Bengal, India. Int J Clin Pediatr Dent 2018;11(2):122-127.

We investigate the electronic structure of epitaxial VO2 films in the rutile phase using density functional theory combined with the slave-spin method (DFT+SS). In DFT+SS, multi-orbital Hubbard interactions are added to a DFT-fit tight-binding model, and slave spins are used to treat electron correlations. We find that while stretching the system along the rutile c-axis results in a band structure favoring anisotropic orbital fillings, electron correlations favor equal filling of the t2g orbitals. These two distinct effects cooperatively induce an orbital-dependent redistribution of the electron occupations and spectral weights, driving strained VO2 toward an orbital selective Mott transition (OSMT). The simulated single-particle spectral functions are directly compared to V L-edge resonant X-ray photoemission spectroscopy of epitaxial 10 nm VO2/TiO2 (001) and (100) strain orientations. Excellent agreement is observed between the simulations and experimental data regarding the strain-induced evolution of the lower Hubbard band. Simulations of rutile NbO2 under similar strain conditions are performed, and we predict that an OSMT will not occur in rutile NbO2. Our prediction is supported by the high-temperature hard x-ray photoelectron spectroscopy (HAXPES) measurement on relaxed NbO2 (110) thin films with no trace of the lower Hubbard band. Our results indicate that electron correlations in VO2 are important, and can be modulated even in the rutile phase before the Peierls instability sets in.