Abstract

Synopsis presentation

Abstract

The superconductor-insulator transition (SIT) is an excellent example of a quantum phase transition, controlled by a non-thermal tuning parameter g, and dominated by quantum fluctuations, which are expected to be prominent near the quantum critical point. So far, most of the experimental studies of the SIT have focussed on transport properties and tunnelling studies, which do not provide quantitative information on the criticality, and on the physics of the quantum fluctuations close to the transition. In our study, we utilize an experimental tool uniquely suited for the study of the evolution of quantum fluctuations through the quantum critical point: the Nernst effect. Nernst effect, in the past has proved to be a very useful tool in the study of superconducting fluctuations, particularly in the case of phase fluctuations mediated by mobile vortices and antivortices. Such fluctuations are important below the superconducting critical temperature TC, and are responsible for having a finite resistance even at a temperature below TC, at which a finite superconducting amplitude ψ¬0 appears.

In our system of amorphous thin film of Indium Oxide, it is believed that the attainment of zero resistance is mediated by pairing of the mobile vortices and antivortices into immobile dipoles, at a temperature TBKT below TC, the transition being a Berezinskii-Kosterlitz-Thouless (BKT) transition. Using resistivity as our tuning parameter g, we take this system through a disorder-induced SIT, and find significant Nernst signals on both the superconducting and insulating sides of the SIT. Analysis of the Nernst coefficient across the SIT shows remarkable qualitative agreement with a model recently developed for the case of Josephson-coupled superconducting chains [1]. We also obtain, for the first time, the scaling behaviour of the off-diagonal Peltier coefficient αyx, a thermodynamic quantity closely related to the Nernst effect, near a disorder-induced SIT.

References:[1] Y. Atzmon and E. Shimshoni, Phys. Rev. B – Condens. Matter Mater. Phys. 87, 1 (2013).

Abstract

The Dark Matter constitutes nearly 26.8% of the total energy budget of the universe as precisely measured by PLANCK and WMAP. One of the attractive candidates for dark matter is a Weakly Interacting Massive Particle(WIMP). A minimal model is proposed which contains one triplet scalar with hypercharge 2 and two vector like fermions: one singlet and a doublet in order to simultaneously explain neutrino mass and dark matter content of the universe.

The dark matter emerges out as a mixed state of the singlet fermion and the neutral component of the doublet. A Z2 symmetry stabilizes the dark matter. The triplet scalar gets an induced vev after the electroweak symmetry breaking and hence give Majorana masses to the neutrinos as well as to the dark matter. Due to the Majorana mass term of the dark matter, the Z mediated direct detection cross-section is forbidden but it can interact with the nuclithrough Higgs mediated chanel and hence can be probed in future running experiments like Xenon-1T. The charged companion of dark matter can give large displaced signature at the LHC.

Abstract

A compressed spectrum pose a serious challenge at LHC. Such a spectrum naturally arises in various BSM scenarios. Monojet with missing pT has been the conventional signal at the LHC. However, we stress that inclusion of $p_T$-binned track observable from such soft objects provide very efficient discrimination of new physics signals against various SM backgrounds. We perform a detailed cut-based and multivariate analysis (MVA) for two benchmark points in MUED and pMSSM scenarios to show that the parameter space of those models can be probed in the ongoing run of LHC at 13 TeV center-of-mass energy with an integrated luminosity 20-50 fb^{-1}.

Abstract

Presentation on the Earthquake Precursor Monitoring Station established at IOP