Condensed Matter Seminar

All future


Wednesday, December 13th 2017
1:25 pm:
Speaker: Wolfram Brenig, Technical University Braunschweig
Subject: Thermal transport in Kitaev-Heisenberg spin systems

Mott insulators with strong spin orbit coupling have become a testbed for exotic quantum phases, spin liquids and emergent Majorana matter. In this context we present results for the thermal conductivity of the Kitaev-Heisenberg model on ladders and the Kitaev model on honeycomb lattices. In the pure Kitaev limit, and in contrast to other integrable spin systems, the ladder represents a perfect heat insulator. This is shown to be a direct fingerprint of fractionalization into mobile Majorana matter and a static Z2 gauge field. We find a full suppression of the Drude weight and a pseudogap in the conductivity. With Heisenberg exchange, we find a crossover from a heat insulator to conductor, due to recombination of fractionalized spins into triplons. Increasing the dimension, and for the 2D honeycomb lattice, we show that very similar behavior occurs with however dissipative heat transport resulting in the thermodynamic limit. Our findings rest on several approaches comprising a mean-field theory, complete summation over all gauge sectors, exact diagonalization, and quantum typicality calculations.

Faculty Host: Natalia Perkins

Wednesday, January 17th 2018
1:25 pm:
Speaker: Jeff Derby (CEMS)
Subject: TBD
Faculty Host: Paul Crowell

Wednesday, January 24th 2018
1:30 pm:
Speaker: Fiona Burnell (University of Minnesota)
Subject: TBD
Faculty Host: Paul Crowell

Wednesday, January 31st 2018
1:30 pm:
Speaker: Sergey Frolov (Pittsburgh)
Subject: Quantum dot chains as emulators of topological superconductors

Tunneling spectroscopy measurements on one-dimensional superconducting hybrid materials have revealed signatures of Majorana fermions which are the edge states of a bulk topological superconducting phase. We couple strong spin-orbit semiconductor InSb nanowires to conventional superconductors (NbTiN, Al) to obtain additional signatures of Majorana fermions and to explore the magnetic-field driven topological phase transition. Specifically, we map out the phase diagram of the topological phase in the space of Zeeman energy and chemical potential, and investigate the apparent closing and re-opening of the superconducting gap. We investigate how the topological superconducting phase would manifest in finite size systems, by electrostatically splitting the wire into segments of varied length. By chaining up several segments of a nanowire, we are realizing a quantum simulator of the Kitaev chain with tunable on-site energies and couplings between the sites, a step towards quantum simulation with semiconductor nanostructures.

Faculty Host: Vlad Pribiag

Wednesday, February 7th 2018
1:30 pm:
Speaker: Cristian Batista (Tennessee)
Faculty Host: Natalia Perkins

Wednesday, February 14th 2018
1:30 pm:
Speaker: Damjan Pelc (University of Minnesota)
Faculty Host: Paul Crowell

Wednesday, February 21st 2018
1:25 pm:
Speaker: Erez Berg (U of Chicago)
Faculty Host: Rafael Fernandes

Wednesday, March 21st 2018
1:25 pm:
Speaker: Pablo Jarillo-Herrero, MIT
Subject: TBD
Faculty Host: Vlad Pribiag

Wednesday, March 28th 2018
1:30 pm:
Speaker: Paul Canfield (Iowa State)
Subject: TBD
Faculty Host: Martin Greven

Wednesday, April 18th 2018
1:30 pm:
Speaker: Ali Yazdani (Tentative)
Faculty Host: Paul Crowell

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