New season

The condensed matter journal club kicked off the new season with a talk by Luke titled Electronic correlations in iron superconductors: insight from optical spectroscopy. Stay tuned for a summary of Luke's talk.

Igor has also started an email listserv which will be used to post updates. Subscribe to keep track of events.

An organization meeting was held last week where we came up with a list of topics and a schedule.
Join the listserv to get a link to the schedule. Feel free to pick a topic (or add one you're interested in) and choose a date for your talk!

Blogon 1: Schwinger Bosons

Opening talk by Tyler Dodds on June 9th, 2011.

Tyler presented a pedagogical talk on Schwinger Boson's with regards to Heisenberg models. Representing spin in terms of boson operators, together with a constraint, was shown to naturally lead to a gapped Z2 spin liquid, or to a magnetically ordered state if the bosons condense.

Last meeting of the Summer: Bosonization II

Journal club talk by Shunsuke Furukawa, continued from Part I.

Furukawa-san discussed 1d spin chains, in particular, the XXZ model. Using the Jordan-Wigner transformation, the spin model was mapped to a system of interacting fermions. The interacting fermions were, in turn, mapped onto a bosonic field theory. Wrapping up, Furukawa-san discussed his own work in mapping out the phase diagram of the XXZ model.

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The journal club is adjourned until the summer of 2011, barring exceptionally interesting developments/papers that members might want to discuss.

Of mean-fields and convergences

Journal club talk by guest speaker Ioannis Anapolitanos
from the Department of Mathematics, UofT, on 26 Aug, 2010.

Reference: http://arxiv.org/abs/0904.4514

We had a lively session of condensed matter mathematics, with Ioannis sketching the status of mean-field theories in mathematical physics. He introduced Hartree mean-field theory for bosonic systems systematically, drawing an analogy to centre of mass motion in classical mechanics.

He then discussed the convergence of expectation values of general p-particle observables in Hartree mean field theory. At the end, he briefly outlined his own work which has improved the bound.

There were interesting discussions about fermionic systems and mixed density matrices.

Introduction to Bosonization

Journal club talk by Shunsuke Furukawa on August 19, 2010

References:
D. Senechal, cond-mat/9908262
F. D. M. Haldane, Phys. Rev. B 25, 4925 (1982).
K. Nomura and K. Okamoto, J. Phys. A 27, 5773 (1994)

Furukawa-san first introduced the idea of bosonization, broadly discussing notions of effective field theory and Luttinger parameter. He then demonstrated the correspondence between a free-fermion-model and a 1d bosonic field theory.
Coming up in Part II: Applications to interacting fermions and spin chains.

Nematicity in the Pseudogap Phase of the Cuprates

Journal club talk by Christoph M. Puetter on August 12, 2010

Reference:
M. Lawler et al., Nature 466, 347, (2010)
(http://www.nature.com/nature/journal/v466/n7304/full/nature09169.html)

Christoph chose this paper, written by the founder of this Journal Club, for an interesting discussion this week. There were broad discussions on the Cuprate phase diagram, nematicity and STM measurements. A lively debate ensued about the key finding of the paper that the nematic order tracks the pseudogap.

Mechanics of energy transfer in light-harvesting antenna proteins: scale-dependent descriptions

Journal club talk by guest speaker Hoda-Hossein Nejad from the Department of Chemistry, UofT, on August 5, 2010

Abstract:
Recent observations of persistent coherence in light-harvesting
antenna proteins pose some interesting questions regarding the role of
quantum effects in photosynthesis: Has nature chosen quantum mechanics as
an strategy for survival? How important are the quantum effects, and on
what scale are these effects significant?

It is plausible to argue that a fully quantum treatment captures the
dynamics of energy transfer on the scale of a few chromophores, but is
both unnecessary and unrealistic for descriptions of long-range energy
transfer between multiple proteins. In this talk,, I will present two
different formulations of the exciton transport problem as applied to the
photosynthetic light-harvesting complex PE545: 1) A fully quantum
description on the scale of a single protein, which takes into account the
interference between pathways leading to a given site. 2) A mixed quantum
classical treatment on the scale of multiple proteins, in which energy
transfer is regarded as a stochastic hop between delocalized eigenstates.