Research areas
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Topological phases
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Correlated electron systems
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Technical approaches
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A topological phase is a macroscopically quantum entangled system of electrons that can arise in solids with a gapped electronic excitation spectrum. For topological reasons their transport responses are very precisely quantized and their boundaries host exotic states that are necessarily gapless. Topological phases hold promise for fundamentally new condensed matter physics phenomena as well as for future technological applications in low-power electronics, spin-based electronics and fault-tolerant quantum computation.
The first examples of topological phases in nature were the time-reversal broken integer and fractional quantum Hall insulators discovered in the early 1980s. However the recent discovery of topological insulators showed that topological phases can also be realized in time-reversal invariant bulk crystals, which has stimulated a widespread search for topological phases in other gapped electronic systems including superconductors, Mott insulators and Kondo insulators just to name a few. We are developing new techniques to identify these new topological phases and to characterize and control their macroscopic quantum properties.
The first examples of topological phases in nature were the time-reversal broken integer and fractional quantum Hall insulators discovered in the early 1980s. However the recent discovery of topological insulators showed that topological phases can also be realized in time-reversal invariant bulk crystals, which has stimulated a widespread search for topological phases in other gapped electronic systems including superconductors, Mott insulators and Kondo insulators just to name a few. We are developing new techniques to identify these new topological phases and to characterize and control their macroscopic quantum properties.
Over the past several decades, there has been intensive research on electronic systems where either electron-electron correlations or spin-orbit coupling is the dominant energy scale, such as the high-Tc superconductors and the topological insulators respectively. However little is known about the regime where the two effects compete on comparable energy scales. Some of the exotic phases that have been theoretically predicted to occur in this regime include fractional topological insulators, unconventional superconductors and spin liquids with non-trivial topological properties.
Recent progress in the materials synthesis of heavy transition metal based compounds such as the 5d transition metal oxides provides a rare opportunity to experimentally explore this previously inaccessible regime. We are developing techniques to probe these materials in search of new broken symmetry or topological phases that emerge from the subtle interplay of strong correlations and strong spin-orbit coupling.
Recent progress in the materials synthesis of heavy transition metal based compounds such as the 5d transition metal oxides provides a rare opportunity to experimentally explore this previously inaccessible regime. We are developing techniques to probe these materials in search of new broken symmetry or topological phases that emerge from the subtle interplay of strong correlations and strong spin-orbit coupling.
We are currently developing a number of novel techniques to search for the types of quantum phenomena in solids described above. These include nonlinear optical spectroscopy, time- and frequency-resolved optical spectroscopy and laser-based angle-resolved photoemission spectroscopy.