# Condensed Matter

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

## Seminar Series Events/Videos

Feb 27 2017 - 10:30am
Room #: 400
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Mar 3 2017 - 4:00pm
Room #: 405
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Mar 7 2017 - 4:00pm
Room #: 301
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Mar 10 2017 - 4:00pm
Room #: 400
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Mar 21 2017 - 3:30pm
Room #: 405
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## Superconductivity near a quantum-critical point --- the special role of the first Matsubara frequency

Tuesday Feb 14, 2017
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Near a quantum-critical point in a metal strong fermion-fermion interaction mediated by a soft collective boson gives rise to incoherent, non-Fermi liquid behavior. It also often gives rise to superconductivity which masks the non-Fermi liquid behavior. We analyze the interplay between the tendency to pairing and fermionic incoherence for a set of quantum-critical models with effective dynamical interaction between low-energy fermions.

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## Generating RVB states in cavity-QED experiments

Tuesday Feb 07, 2017
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Dicke's seminal 1954 paper introduced the notion of `superradiance' in a system of spins coupled to a common photon mode.

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## Emergent Chiral Spin Liquids in Frustrated Magnetism

Friday Jan 20, 2017
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Topological states of matter are of of fundamental interest in contemporate condensed matter physics. Today, the fractional Quantum Hall effect remains the only known experimental system expected to exhibit intrinsic topological order. The question remains whether also different systems might stabilize this kind of ordering. Chiral spin liquids are an analogue of Fractional Quantum Hall Effect wave functions for spin systems.

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## Orders and disorder in high-Tc superconductors

Friday Jan 13, 2017
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Since its first discovery in 1986, high-Tc superconductors have been attracting constant interests and meticulous efforts from both theorists and experimentalists, not merely due to its large transition temperature, but also because it offers a well characterized laboratory for the study of exotic phenomena such as quantum criticality, non-Fermi liquid behavior, and intertwined orders. One pressing question in the field is the role played by disorder:

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## RG flows and Boundary States in 2d CFTs

Tuesday Jan 10, 2017
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## From skein theory to presentations of Thompson groups

Tuesday Jan 10, 2017
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Motivated by the question about reconstructing a Conformal field theory from the data of a subfactor of finite index, Jones studied the continuous limit of the periodic quantum spin chain which Thompson group acts on. Based on planar algebras, the topological axiomatization of subfactors, we will illustrate the idea of the correspondence between the skein theory of planar algebras and presentation of Thompson groups.

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## Theory and Experimental Platform for Bosonic Symmetry Protected Topological Phases

Tuesday Dec 20, 2016
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Bosonic symmetric protected topological (BSPT) phases are bosonic anagolue of electron topological insulators and superconductors. Despite the theoretical progresses of classifying these states, little attention has been paid to experimental realization of BSPT states in dimensions higher than 1. We propose bilayer graphene system in a out-of-plane magnetic field with Coulomb interaction is a natural platform for BSPT states with $U(1)\times U(1)$ symmetry.

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## Matrix product state evolutions of quantum fields in curved space

Thursday Dec 15, 2016
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The matrix product state (MPS) ansatz makes possible computationally-efficient representations of weakly entangled many-body quantum systems with gapped Hamiltonians near their ground states, notably including massive, relativistic quantum fields on the lattice. No Wick rotation is required to apply the time evolution operator, enabling study of time-dependent Hamiltonians. Using free massive scalar field theory on the 1+1 Robertson-Walker metric as a toy example, I present early efforts to exploit this fact to model quantum fields in curved spacetime.

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## Entanglement negativity in topologically ordered phases

Tuesday Dec 13, 2016
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Unlike entanglement entropy and mutual information which may mix both classical and quantum correlations, entanglement negativity received extensive interest recently, for its merit of measuring the pure quantum entanglement in the system. In this talk, I will introduce the entanglement negativity in 2+1 dimensional topologically ordered phases. For a bipartitioned or tripartitioned spatial manifold, we show how the universal part of entanglement negativity depends on the presence of quasiparticles and the choice of ground states.

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## Majorana zero modes in condensed matter: From topological quantum computing milestones to Majorana-dimer models

Friday Dec 09, 2016
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Condensed matter realizations of Majorana zero modes constitute potential building blocks of a topological quantum computer and thus have recently been the subject of intense theoretical and experimental investigation. In the first part of this talk, I will introduce a new scheme for preparation, manipulation, and readout of these zero modes in semiconducting wires coated with mesoscopic superconducting islands.

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