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 …

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 …

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 …

Erhai Zhao’s research interests

Many body physics of ultracold quantum gases

Ultracold gases refer to quantum degenerate gases of atoms (such as Rubidium, Potassium or Lithium) or molecules confined in vacuum by laser beams and cooled down to nano-Kelvin temperatures (one billionth degree above absolute zero). These systems offer well-controlled settings to test and advance our basic understanding of the collective behaviors of …

Frustrated Quantum Magnets

At the frontier of our efforts to understand collective phenomena is the search for unconventional phases of matter. Many ideas for exotic phases shaped by strong quantum fluctuations have been explored in recent years, motivated by the difficulty of explaining various strongly correlated materials, such as cuprates and heavy fermion systems. Perhaps the most promising platform for characterizing and observing such phases are geometrically frustrated quantum magnets.

High-Temperature Superconductivity

High temperature superconductivity of cuprates is one of the greatest challenges in many-body quantum physics. Since their discovery in 1986, the field of condensed matter physics has been flooded with an enormous number of new ideas, theoretical and experimental techniques. While the superconducting phenomenology in cuprates has been understood very well, the origin of superconductivity is still mysterious. It is believed that the secret to high temperature superconductivity is hidden in the strong correlations that electrons experience in the so called “normal” and “pseudogap” states. Several experimental and theoretical developments suggested that certain aspects of pseudogap dynamics may result from a quantum liquid state of vortices that destroy the long-range phase coherence of robust Cooper pairs.

Ultra-cold fermionic atoms near unitarity

In recent years, atomic physics has opened a new frontier for the exploration of strongly correlated many-body systems. Atoms can be cooled to sub-nanokelvin temperatures, trapped in a small volume and placed in artificial crystalline potentials or electromagnetic fields created by lasers. Furthermore, interactions between atoms can be controlled. This enables simulations of electronic materials with more ideal properties than found in nature, and testing or developing theories of condensed matter in a new environment. Novel forms of quantum matter can also be engineered using ultra-cold atoms.

Fractional Topological Insulators

A new class of materials with strong spin-orbit coupling, known as topological insulators (TI), are bulk insulators with edge or surface conduction channels that respect the time-reversal (TR) symmetry. In that sense they are similar to quantum Hall systems, which however are not invariant under TR due to the externally applied magnetic field. The Rashba spin-orbit coupling found in TI materials has a “dynamical” symmetry that can shape incompressible quantum liquids in the presence of strong quantum fluctuations, without an analogue in quantum Hall states. Such quantum liquids can exhibit new and not yet experimentally discovered topological orders with Abelian or non-Abelian fractional statistics.