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Novel chiral Bose liquid discovered

A team of researchers to which CUI Professor Andreas Hemmerich belongs proposes an experiment which will directly detect chiral order. Such a direct observation has been thought to be impossible.

Ultracold quantum gases in optical lattices offer unique possibilities to experimentally unravel the physics behind exotic quantum phases under well-controlled conditions in a lab.  Using such experimental model systems researchers have recently demonstrated that p-orbital Bose systems can exist in a novel state of matter which exhibits both superfluidity and chiral order at the same time.

ChiralFluids-FeaturedImage

Illustration of a chiral order in a two dimensional checkerboard optical lattice. The orbital configuration shown here exhibits staggered angular momentum. Adding an additional lattice potential shown by the pink curve, the chiral order implies novel dynamical phenomena in band-population dynamics.

Extending these studies an international team of scientists has investigated how thermal fluctuations destroy the characteristics of such chiral superfluids. Their theoretical study, which appears in Nature Communications, is predicting a novel regime that appears between a chiral superfluidic phase at low temperatures and the normal liquid high temperature state. With increasing temperatures thermal fluctuations destroy first superfluidity, however, the chiral order unexpectantly persists. Only at even higher temperatures an Ising-like transition will take the chiral Bose liquid in a usual liquid state without local chirality.

In addition to their theoretical analysis, the authors propose an experimental way that allows the direct observation of chiral order in an experiment. “For a long time chiral order could only be observed indirectly”, says Prof. Hemmerich. “We are currently setting up an experiment where we apply our ideas.” The scientists propose a rapid quench of the lattice potential which will convert the staggered angular moments into coherent oscillations which will directly show the chiral order. Such experiments require a delicate control of conditions. Prof. Hemmerich: “This is extremely challenging.”

Original: X. Li, A. Paramekanti, A. Hemmerich, and W. V. Liu, Proposed formation and dynamical signature of a chiral Bose liquid in an optical lattice, Nature Communications, Vol. 5, 3205 (2014), doi:10.1038/ncomms4205.