Talks

Inspired by the observation of crystallization of the vortices in the intermediate field range in a Kitaev model [Phys. Rev B 108, 165118 (2023)], we delve into obtaining different superlattice formations of the vortices and the corresponding Majorana dispersions. This gives a novel possibility of governing flat bands for Majoranas and other possible excitations that may arise in analogous settings. We find several superlattice configurations of vortices where Majorana states are weakly dispersive or even fully flat with or without a gap. The gapped flat bands have a non-zero Chern number with a higher quantum metric value (bandwidth) tunable by varying applied magnetic fields. Having satisfied the ‘vortexibility condition,’ these bands can harbor fractional Chern insulator phase of the emergent Majorana fermions if appropriate interactions are present. Interestingly, we have used the projection method and maximally localized Wannier functions algorithm to identify the localizing c...

We propose an effective Hamiltonian approach to understand a variety of partially magnetically ordered phases in a Kondo lattice. Such partial order, where only selected sites are Kondo-screened while the others develop local moments, have been observed in many heavy-fermion compounds. The proposed effective Hamiltonian retains two important features of the fundamental Kondo-lattice model: (i) formation of a Kondo singlet leading to vanishing of the local magnetic moment, and (ii) spatially correlated nature of the electronic kinetic energy. The Hamiltonian belongs to a class of coupled classical-quantum models that can be reliably studied using hybrid Monte Carlo simulations. I will try to motivate the model and demonstrate the approach for the case of a square lattice where we unveil a number of magnetic phases with partial order. I will further motivate a fully classical spin model to describe the partial magnetic order in Kondo lattices.

In this talk I will discuss transport experiments on twisted WSe2 layers that show evidence for magnetic states, and also superconductivity. I will discuss the relationship between the two phases in the phase diagram.

Gaining control over the electronic and magnetic phenomena in solids is a critical step to advance our understanding that can have technological implications. Thin film interfaces and layered materials offer a wide range of possibilities to engineer new phases of electron matter. In the first part of this talk, I will discuss about realizing topological electron transport in SrCuO2 (001)/SrIrO3 (001) epitaxial thin films [1]. When SrIrO3 is proximitized with an antiferromagnetic SrCuO2 layer, we observe an enhancement of effective phase coherence length (lφ) and the chiral anomaly induced topological response in longitudinal magnetoconductance (B‖E) (which is absent in bare SrIrO3 film). Both the above effects is discussed in view of possible quenching of undesired magnetic impurity scattering through antiferromagnetic proximity effect. In the last part of the talk, I will discuss about notable halide ligand tunability of non-collinear magnetism in Cu-based quasi 2D hybrid perovskites....

1T-TaS2 exhibits several resistivity phases due to the modulation of charge density wave (CDW). The fact that such phase transition can be driven electrically has attracted a lot of attention in the recent past toward active-metal based electronics. However, the bias-driven resistivity switching is not very large (less than five-fold), and an enhancement in the same will highly impact such phase transition devices. One aspect that is often overlooked is that such phase transition is also accompanied by a significant change in the local temperature due to the low thermal conductivity of 1T-TaS2. In this work, such electrically driven phase transition induced temperature change is exploited to promote carriers over a thermionic barrier in a 1T-TaS2/2H-TaSe2/2H-MoS2 T-Junction, achieving a 964-fold abrupt switching in the current through the MoS2 channel. The device is highly reconfigurable and exhibits an abrupt reduction in current as well when the biasing configuration changes. The res...

In recent years, tuning electrical polarization by magnetic field and vice versa in multiferroic and magnetoelectric materials received much attention. Impedance spectroscopy is frequently used to probe magnetic-field dependence of capacitance in these materials. However, impedance spectroscopy has been rarely used to study metallic or semiconducting oxides above 1 MHz and below 10 GHz. In this talk, I will show selected applications of the impedance spectroscopy to electrically detect spin resonance, domain magnetization processes and spin/charge conversion. Extension of this technique to 2D materials will also be outlined.

Cuscuton field theory is an extension of general relativity that does not introduce additional propagating degrees of freedom, or violate relativistic causality. We construct a general geometric description of the cuscuton field theory by introducing curvature corrections to both the volume (potential) and the surface (kinetic) terms in the original cuscuton action. Our assumptions involve a stack of spacelike branes, separated by 4-dimensional bulks. We conjecture that the cuscuton, initially a discrete field, becomes continuous in the limit, there are many such transitions. From this we derive an effective action for the cuscuton theory and show that at the quadratic level our theory propagates only the two tensorial degrees of freedom.

I will first introduce screened modified gravity theories and then discuss the chameleon mechanism. Light scalars can be produced from the sun and detected on earth. I will discuss the production of chameleons, including novel production channels, and discuss potential detection in helioscopes.