Condensed Matter

This series consists of talks in the area of Condensed Matter.

Seminar Series Events/Videos

Currently there are no upcoming talks in this series.

 

Friday Sep 16, 2011
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We investigate the entanglement spectra of topological insulators which have gapless edge states on their spatial boundaries. In the physical energy spectrum, a subset of the edge states that intersect the Fermi level translates to discontinuities in the trace of the single-particle entanglement spectrum, which we call a `trace index'. We find that any free-fermion topological insulator that exhibits spectral flow has a non-vanishing trace index, which provides us with a new description of topological invariants.

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Wednesday Sep 14, 2011
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Time-reversal invariant band insulators can be separated into two categories: `ordinary' insulators and `topological' insulators. Topological band insulators have low-energy edge modes that cannot be gapped without violating time-reversal symmetry, while ordinary insulators do not. A natural question is whether more exotic time-reversal invariant insulators (insulators not connected adiabatically to band insulators) can also exhibit time-reversal protected edge modes.

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Monday Aug 29, 2011
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Strongly correlated electron systems are play grounds for exotic quantum states such as high Tc superconductivity, quantum spin liquids, non-fermi liquids and so on. Recently high Tc superconductivity has been observed in an iron based compound K2Fe4Se5. I will present a model and outline an effective theory [1] that describes physics of this complex system - a non linear O(3) sigma model in 2 + 1 dimensions coupled to Dirac fermions. Topological solitons and induced quantum numbers are well known in Skyrme model for protons and neutrons.

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Friday May 13, 2011
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We discuss bulk and holographic features of black hole solutions of 4D anti de Sitter Einstein-Maxwell-Dilaton gravity. At finite temperature the field theory holographically dual to these solutions has a rich and interesting phenomenology reminiscent of electron motion in metals:
phase transitions triggered by nonvanishing VEV of scalar operators, non-monotonic behavior of the electric conductivities etc. Conversely, in the zero temperature limit the transport properties for these models show an universal behavior.

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Friday May 06, 2011
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The equilibration dynamics of a closed quantum system is encoded in the long-time distribution function of generic observables. In this paper we consider the Loschmidt echo generalized to finite temperature, and show that we can obtain an exact expression for its long-time distribution for a closed system described by a quantum XY chain following a sudden quench.

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Monday Mar 28, 2011
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We will discuss the effect of non-equilibrium drive near a quantum
critical point in itinerant electron systems. Non-equilibrium field
theory is formulated in terms of the Keldysh functional integral.
The renormalization group approach is used to study the universality
class of the non-equilibrium phase transition in the steady state system.
The role of the non-equilibrium drive in the quantum-classical crossover
will be discussed using the example of the Hertz-Millis theory and
the generalization thereof.

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Friday Feb 11, 2011
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We consider one dimensional devices supporting a pair of Majorana bound states at their ends We firstly show [1] that edge Majorana bound modes allow for processes with an actual transfer of electronic material between well-separated points and provide an explicit computation of the tunnelling amplitude for this process.

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Friday Jan 28, 2011
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The simulation of systems of anyons offers a significant challenge to
the condensed matter physicist. These systems are presently of
substantial theoretical and experimental interest due to their potential
for universal quantum computation, but due to their non-trivial exchange
statistics, the tools available for their study have been limited. In
this talk, I will present a formalism whereby any existing tensor
network algorithm may be adapted for use with both Abelian and
non-Abelian anyons, culminating in our recent simulations of infinite

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Thursday Dec 16, 2010
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Anderson localization emerges in quantum systems when randomised parameters cause the exponential suppression of motion. In this talk we will consider the localization phenomenon in the toric code, demonstrating its ability to sustain quantum information in a fault tolerant way. We show that an external magnetic field induces quantum walks of anyons, causing logical information to be destroyed in a time linear with the system size when even a single pair of anyons is present.

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