# 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.

## Bosonization and the shear sound of metals

Tuesday Sep 24, 2019
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We will review the bosonization approach to Fermi liquids in dimensions above one. We will use this to study a sharp change in the neutral excitation spectrum of fermi liquids that occurs beyond a critical interaction strength whereby an unconventional collective mode exits the particle-hole continuum. This mode is a collective shear wave that features purely transverse current oscillations, in analogy to the transverse sound of crystals. Because it is hard to “see" due to its transversal nature, the shear sound might be already “hiding`' in several metals.

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## Entanglement entropy, quasiparticle fluctuations, and 1D thermal entropy in topological phases

Tuesday Sep 17, 2019
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Entanglement entropy in topologically ordered matter phases has been computed extensively using various methods. In this talk, we study the entanglement entropy of 2D topological phases from the perspective of quasiparticle fluctuations. In this picture, the entanglement spectrum of a topologically ordered system encodes the quasiparticle fluctuations of the system, and the entanglement entropy measures the maximal quasiparticle fluctuations on the entanglement boundary.

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## A solvable model for magnetic skyrmions

Friday Sep 13, 2019
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Magnetic skyrmions are topological solitons which occur in a large class of ferromagnetic materials and which  are currently attracting much attention, not least because of their potential use for  low-energy magnetic information storage and manipulation. The talk is about an integrable model for magnetic skyrmions, introduced in a recent paper (arxiv:1812.07268) and generalised in  arxiv:1905.06285.

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## Inversion-protected higher-order topological superconductivity in monolayer WTe2

Tuesday Sep 10, 2019
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Monolayer WTe2, an inversion-symmetric transition metal dichalcogenide, has recently been established as a quantum spin Hall insulator and found superconducting upon gating.

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## Real-space recipes for general topological crystalline states

Tuesday Sep 03, 2019
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Topological crystalline states are short-range entangled states jointly protected by onsite and crystalline symmetries. While the non-interacting limit of these states, e.g., the topological crystalline insulators, have been intensively studied in band theory and have been experimentally discovered, the classification and diagnosis of their strongly interacting counterparts are relatively less well understood. Here we present a unified scheme for constructing all topological crystalline states, bosonic and fermionic, free and interacting, from real-space "building blocks" and "connectors".

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## Order by Singularity

Thursday Aug 15, 2019
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We present a paradigm for effective descriptions of quantum magnets. Typically, a magnet has many classical ground states — configurations of spins (as classical vectors) that have the least energy. The set of all such ground states forms an abstract space. Remarkably, the low energy physics of the quantum magnet maps to that of a single particle moving in this space.

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## Quantum Link models to probe new aspects of gauge theories

Friday Aug 09, 2019
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The Wilson formulation of lattice gauge theories provides a first-principles study of many properties of strongly interacting theories, such as quantum chromodynamics (QCD). Certain other properties, such as real-time dynamics, pose insurmountable challenges in this paradigm. Quantum Link Models are generalized lattice gauge theories, which not only offer novel approaches to study dynamics of gauge theories with quantum simulators, but also connect to

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## Spins on a Kagome Lattice: Topological Magnons

Tuesday Aug 06, 2019
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In this talk, I will focus on topological aspects and edge states of a spin system on a Kagome lattice. with the anisotropic XXZ and Dzyaloshinskii-Moriya interaction (DMI). I will begin with the rich phase diagram in the classical limit arising as a result of the interplay of the two interaction strengths, followed by a spin-wave analysis in some of these phases.

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## Stable Flat Bands, Topology, and Superconductivity of Magic Honeycomb Network

Tuesday Jul 30, 2019
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We uncover a rich phenomenology of the self-organized honeycomb network superstructure of one-dimensional metals in a nearly-commensurate charge-density wave 1T-TaS${}_2$, which may play a significant role in understanding global topology of phase diagrams and superconductivity. The key observation is that the emergent honeycomb network magically supports a cascade of flat bands, whose unusual stability we thoroughly investigate.

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## Self-learning Monte Carlo method and structured self-attention network

Tuesday Jul 16, 2019
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Self-learning Monte Carlo (SLMC) method is a general-purpose numerical method to simulate many-body systems. SLMC can efficiently cure the critical slowing down in both bosonic and fermionic systems. Moreover, for fermionic systems, SLMC can generally reduce the computational complexity and speed up simulations even away from the critical points. For example, SLMC is more than 1000 times faster than the conventional method for the double exchange model in 8*8*8 cubic lattice.

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## LECTURES ON-DEMAND

### Gabriela González, Louisiana State University

Speaker: Gabriela Gonzalez