Frustration shapes multi-channel Kondo physics: a star graph perspective.

We study the overscreened multi-channel Kondo (MCK) model using the recently developed unitary renormalisation group technique. Our results display the importance of ground state degeneracy in explaining various important properties like the breakdown of screening and the presence of local non-Fermi liquids (NFLs). The impurity susceptibility of the intermediate coupling fixed point Hamiltonian in the zero-bandwidth (or star graph) limit shows a power-law divergence at low temperature.

The effect of antisite disorder on magnetic and exchange bias properties of Gd-substituted YCoMnOdouble perovskite.

Combining experimental investigations and first-principles density functional theory (DFT) calculations, we report physical and magnetic properties of Gd-substituted YCoMnOdouble perovskite, which are strongly influenced by antisite-disorder-driven spin configurations. On Gd doping, Co and Mn ions are present in mixed-valence (Co, Co, Mnand Mn) states. Multiple magnetic transitions have been observed: (i) paramagnetic to ferromagnetic transition is found to occur at= 95.

Dynamic chiral magnetic effect and anisotropic natural optical activity of tilted Weyl semimetals.

We study the dynamic chiral magnetic conductivity (DCMC) and natural optical activity in an inversion-broken tilted Weyl semimetal (WSM). Starting from the Kubo formula, we derive the analytical expressions for the DCMC for two different directions of the incident electromagnetic wave. We show that the angle of rotation of the plane of polarization of the transmitted wave exhibits remarkable anisotropy and is larger along the tilt direction.

Slave rotor approach to exciton condensation in a two-band system.

We have studied exciton formation and condensation in an extended Falicov-Kimball model, going beyond the weak coupling approach, employing a semi-analytical technique: the slave-rotor mean-field theory (SRMF). In this essentially strong coupling theory, charge and spin (or orbital/pseudospin) degrees are treated as independent degrees of freedom, coupled by a local constraint. Using a two-site-extension of SRMF, we capture the effective many body scale beyond conventional mean-field theory.

Berry phase theory of planar Hall effect in topological insulators.

The appearance of negative longitudinal magnetoresistance (LMR) in topological semimetals such as Weyl and Dirac semimetals is understood as an effect of chiral anomaly, whereas such an anomaly is not well-defined in topological insulators. Nevertheless, it has been shown recently in both theory and experiments that nontrivial Berry phase effects can give rise to negative LMR in topological insulators even in the absence of chiral anomaly. In this paper, we present a quasi-classical theory of another intriguing phenomenon in topological insulators - also ascribed to chiral anomaly in Weyl and Dirac semimetals- the so-called planar Hall effect (PHE).