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# 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.

## Spin fractionalization on a Pyrochlore Lattice

Mardi mai 28, 2013
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The decomposition of the magnetic moments in spin ice into freely moving magnetic monopoles has added a new dimension to the concept of fractionalization, showing that geometrical frustration, even in the absence of quantum fluctuations, can lead to the apparent reduction of fundamental objects into quasi particles of reduced dimension [1]. The resulting quasi-particles map onto a Coulomb gas in the grand canonical ensemble [2]. By varying the chemical potential one can drive the ground state from a vacuum to a monopole crystal with the Zinc blend structure [3].

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## Novel s-wave superconducting phase of doped topological insulators.

Jeudi mai 23, 2013
Speaker(s):

Many of the topological insulators, in their naturally
available form are not insulating in the bulk. It has been  shown that some of these metallic compounds,
become superconductor at low enough temperature and the nature of their
superconducting phase is still widely debated. In this talk I show that even
the s-wave superconducting phase of doped topological insulators, at low
doping, is different from ordinary s-wave superconductors and goes through a
topological phase transition to an ordinary s-wave state by increasing the

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## Neutrino as Majorana zero modes

Mardi mai 14, 2013

The existence of three generations of neutrinos and their mass mixing is a deep mystery of our universe. Majorana's elegant work on the real solution of Dirac equation predicted the existence of Majorana particles in our nature, unfortunately, these Majorana particles have never been observed. In this talk, I will begin with a simple 1D condensed matter model which realizes a T^2=-1time reversal symmetry protected superconductors and then discuss the physical property of its boundary Majorana zero modes.

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## Unconventional Magnetism and Superconductivity in 3 Dimensional Doped Mott Insulators

Mardi avr 30, 2013
Speaker(s):

Utilizing a variety and also
constraints offered by quantum and solid

state chemistry, we discuss
possibilities of unconventional quantum

magnetism and superconductivity
in doped 3 dimensional Mott insulators.

Some of the possibilities are
quantum spin liquid states having pseudo

fermi surface coexisting with
long range magnetic order, 3 dimensional

emergent gauge fields and
unconventional superconducting order parameter

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## Quantum transport in one dimension: from integrability to many-body localization and topology

Mardi avr 23, 2013
Speaker(s):

Recent advances in analytical theory and numerical methods
enable some long-standing questions about transport in one dimension to be
answered; these questions are closely related to transport experiments in
quasi-1D compounds.  The spinless fermion chain with nearest-neighbor
interactions at half-filling, or equivalently the XXZ model in zero magnetic
field, is an example of an integrable system in which no conventional conserved
quantity forces dissipationless transport (Drude weight); we show that there is

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## Topological insulator of bosons in 3d via dyon condensation and the statistical Witten effect.

Mercredi avr 10, 2013
Speaker(s):

In
this talk, I will construct a symmetry protected topological phase of bosons in
3d with particle number conservation and time reversal symmetries, which is the
direct bosonic analogue of the familiar electron topological insulator. The
construction employs a parton decomposition of bosons, followed by condensation
of parton-monopole composites. The surface of the resulting state supports a
gapped symmetry respecting phase with intrinsic toric code topological order
where both e and m anyons carry charge 1=2.

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## S=1 spin liquid with fermionic excitations

Jeudi mar 28, 2013
Speaker(s):

In the first part of my talk I describe a search for
possible quantum spin liquid ground states for spin S=1 Heisenberg models on
the triangular lattice which was motivated by recent experiments on
Ba3NiSb2O9.  We use representation of
spin-1 via three flavors of fermionic spinon operators. The ground state where
one gapless flavor of spinons with a Fermi surface coexists with d+id
topological pairing of the two other flavors can explain available experimental

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## Classifying fractionalization: symmetry classification of gapped Z2 spin liquids in two dimensions

Mardi mar 26, 2013
Speaker(s):

Quantum number fractionalization is a remarkable property
of topologically ordered states of matter, such as fractional quantum Hall
liquids, and quantum spin liquids. For a given type of topological order, there
are generally many ways to fractionalize the quantum numbers of a given
symmetry. What does it mean to have different types of fractionalization? Are
different types of fractionalization a universal property that can be used to
distinguish phases of matter? In this talk, I will answer these questions,

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## One-photon and two-photon switching in graphene and optical nanomaterials

Vendredi mar 08, 2013
Speaker(s):

In this talk we will discuss both the one-photon and
two-photon switching mechanisms in hybrid nanomaterials made from two or more
semiconductor, metallic and optical nanostructures. The most prominent examples
of these nanostructures are graphene, semiconductor quantum dots, metallic
nanoparticles, and photonic and polaritonic crystals. Advances in nanoscience
have allowed for the construction of these new classes of hybrid nanomaterials.
Optical excitations in semiconductor nanostructures are electron-hole pairs

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## Gravitational anomaly and topological phases

Jeudi fév 28, 2013
Speaker(s):

Since the quantum Hall effect, the notion of topological
phases of matter has been extended to those that are well-defined (or:

protected'') in the presence of a certain set of
symmetries, and that exist in dimensions higher than two. In the (fractional)
quantum Hall effects (and in chiral'' topological phases in general),
Laughlin's thought experiment provides a key insight into their topological
characterization; it shows a close connection between topological phases and
quantum anomalies.

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