Effect of electron-hole asymmetry on optical conductivity in 8-Pmmn borophene
Abstract
8-Pmmn borophene is a polymorph of borophene that exhibits anisotropic tilted Dirac cones. In our work, we have done a detailed theoretical study of the optical conductivity of 8-Pmmn borophene. We provide exact analytical expressions of the maximum optical conductivity. We also obtain exact analytical expressions of the minimum energy (1) required to trigger the inter-band optical transitions and energy (2) needed to attain maximum optical conductivity. We find that the optical conductivity are highly anisotropic as a consequence of the anisotropic Dirac cone. The optical conductivities have a non-monotonic behavior with photon energy in the regime between 1 and 2, as a result of the tilted parameter . The tilted parameter can be extracted by knowing 1 and 2 from optical measurements.
The maximum values of the components of the optical conductivity do notdepend on the carrier density and the tilted parameter. The product of the maximum values of the anisotropic conductivities has the universal value (e2=4h2 ). The tilted anisotropic Dirac cones in 8-Pmmn borophene can be realized by the optical conductivity measurement.
Reference: S.Verma, A. Mawrie and T. K. Ghosh, Physical Review B 96, 155418 (2017).
13/11/2017 at 4:00 pm
Professor Sreerup Raychaudhuri, TIFR, Mumbai
Colloquium
IOP Lecture Hall
Document Date:
The early history of particle physics research in India
Phenomenology of Universal Extra Dimensional Models
Abstract
In this talk, we will discuss Universal Extra Dimensional models (UED) in its basic and non-minimal version (nmUED). Non-minimality in Universal Extra Dimensional (UED) framework is realized by adding boundary localized terms (BLT). We will discuss the unitarity constraints in gauge and scalar sectors. We shall show that some of the tree-level two-body scattering amplitudes in gauge and scalar sectors do not respect partial wave unitarity. Unitarity of scalar sector of this model leads to an upper bound on gauge or scalar BLT parameter which depends on the maximum number of Kaluza-Klein (KK) mode considered in the analysis. We shall also show the limit on compactification radius of UED in view of the Zbb coupling. For suitable choice of BLT parameters (which is permissible from unitarity analysis), 95% C.L. lower limit on inverse of compactification radius comes out to be in the range of 1 TeV in the framework of nmUED. Finally, we will discuss some flavor changing top quark decays. In UED these decay rates do not change much from their Standard Model (SM) values. However, in nmUED these decay rates can be higher than SM for specific choices of the BLT parameters for a certain range of inverse compactification radius. But these model parameters may lead to Kaluza-Klein particle masses that are in tension with the LHC and LEP bounds.
03/11/2017 at 4:00 pm
Sabya Sachi Chatterjee
HEP Seminar
Lecture Hall Block A, Institute of Physics
Document Date:
Exploring Light Sterile Neutrinos and Long-Range Forces in Long-Baseline Experiments
