A topological ladder

The orbital degrees of freedom refer to different shapes of the wave functions with degenerate energies. In recent years, optical lattices engineered by interfering laser beams offer new means to explore interacting fermions with orbital degrees of freedom the symmetries of which differ from those found in traditional solids. We show that the orbital hopping pattern alone is sufficient for producing topologically non-trivial band structures. We unveil a topological insulator phase of fermions on a two-leg ladder of  double-well lattices, similar to those recently realized in experiments.

 

 

Topological orbital ladders, Xiaopeng Li, Erhai Zhao, W. Vincent Liu, arXiv:1205.0254

http://arxiv.org/abs/1205.0254

Phase diagram of dipolar Fermi gases


Understanding the quantum phases of interacting fermions is a fundamental, chanllenging problem in many-body physics. Broken symmetry phases, such as spin density wave order in antiferromagnetic metal Chromium, or the p-wave superfluid order in liquid Helium 3, have long been known and well understood. Motivated by recent experiments, we find theoretically that an unconventional spin-density wave phase with p-wave orbital symmetry in ultracold Fermi gases of polar molecules and magnetic atoms. It is a kind of magnetic order formed on bonds connecting the lattice sites, and can be viewed as the particle-hole analog of p-wave superconductivity.

 

Unconventional Spin Density Waves in Dipolar Fermi Gases, S. G. Bhongale, L. Mathey, Shan-Wen Tsai, Charles W. Clark, Erhai Zhao, arXiv:1209.2671

http://arxiv.org/abs/1209.2671

Krishna Vemuru’s research interests

Magnetic nanostructures

Synthesis and characterization of magnetic nanostructures is an important aspect of research in nanoscience.  In order to improve the characteristics of nanomaterials based devices, it is important to understand the structure property relation as well as the mechanism of the magnetic ordering. The goal of our research is to investigate the suitability of nanostructured magnetic materials  for applications in high density magnetic data storage such as magnetic tapes, and hard disk media. Some of these nanostructures are rodlike metallic iron nanopartcles g-Fe2O3 nanoparticles,  PZT thin films with Co nanostructures,  Co/Fe multilayers, core-shell structured FePtM (M= Au, Cu) nanoparti nanoparticles. The orientatonal ordering of nanostructures are investigated using small angle neutron scattering, and element specific magnetic behavior  is determined using x-ray magnetic circular dichroism spectroscopy.

Mingzhen Tian’s research interests

Laser atomic spectroscopy, nonlinear and quantum optics, and quantum information science.

Currently focused on rare-earth based solid state quantum memory and quantum computation, which are the important components in developing quantum information science and technology.  The research also include investigation of laser spectroscopic properties of rare-earth ions trapped in inorganic crystal lattice at cryogenic temperature, the coherent and incoherent processes under the excitation of composite laser pulses, and the influence of the static electric and magnetic fields. Study of these processes provides the information needed to understand and control the physical systems to demonstrate quantum memory and robust quantum logic gates. Research activities involve both experiments and theoretical modeling. Student research projects are currently carried out at both graduate and undergraduate levels.

 

Current projects:

  1. Rare-earth ensemble based solid state quantum memory.
  2. Robust quantum logic gates based on geometric phase.
  3. Multipartite entanglement in GHZ diagonal states.