# Events Archive

## Condensed Matter Seminar

### Special Condensed Matter Seminar-Monica Allen, Harvard U-"Spatially resolved edge currents & ballistic interference in a graphene Josephson junction"

Tue, Dec 8, 2015, 1:00 pm to 2:00 pm

Graphene provides an appealing platform to explore electronic analogs of optical effects due to the nonclassical nature of ballistic charge transport. Inspired by guiding of light in fiber optics, we demonstrate a means to guide the flow of electrons at the edges of a graphene crystal near charge neutrality.

### Condensed Matter Seminar, Ady Stern, Weizmann Inst., "Fractionalized edge phases"

Mon, Dec 7, 2015, 1:15 pm to 2:30 pm

Edges of gapped topological states may host gapless edge modes that cannot be realized as stand-alone systems. Examples include quantum Hall edge states, surface states of topological insulators and super-conductors, etc. In my talk I will examine situations in which these edge states form fractionalized phases of their own.

### CM Seminar, Avraham Klein, Hebrew University of Jerusalem, "Vortex core deformation in weakly coupled superfluids"

Mon, Nov 30, 2015, 1:15 pm to 2:30 pm

Quantum vortices in weakly coupled superfluids have a large healing length, so that many particles reside within the vortex core. They are characterized by topologically protected singular points, which in principal should keep their core structure rigid.

### Special Physics/CM Seminar, Umesh Vazirani, UC Berkeley, "Algorithms and area laws for low-energy eigenstates in 1D quantum systems"

Fri, Nov 20, 2015, 4:00 pm to 5:30 pm

One of the central challenges in the study of quantum many-body systems is the exponential complexity of simulating them on a classical computer. A rare bright spot is the heuristic DMRG (Density Matrix Renormalization Group) which has been widely used, ever since its invention almost a quarter century ago, for solving 1D systems.

### Special Condensed Matter Seminar, Ville Lahtinen, Freie U, Berlin,"Self-organized pseudo-graphene on grain boundaries in topological band insulators"

Wed, Nov 18, 2015, 1:30 pm to 2:30 pm

Semi-metallic materials, such as graphene in two dimensions (2D) and various Dirac and Weyl semi-metals in three dimensions (3D), are characterized by nodal band structures that give rise to exotic electronic properties.

### Special CM Seminar, Xiao Hu, NIMS, Japan, "Topological States in Honeycomb Structures"

Tue, Nov 17, 2015, 1:30 pm to 3:00 pm

The honeycomb lattice plays an extremely important role in fostering the concept of topology in materials, as seen in the pioneer works by Haldane and by Kane and Mele. In this talk, I revisit electronic states in a honeycomb lattice and try to better highlight the uniqueness of the honeycomb structure.

### Chen Fang. MIT, "Topological gapped and gapless phases protected by nonsymmorphic lattice symmetries"

Mon, Nov 16, 2015, 1:15 pm to 2:30 pm

In the first part of the talk, I will show that a nonsymmorphic glide reflection symmetry can protect a new Z2 topological gapped phase in three-dimensions. Unlike topological insulators, this new phase can be realized in either spinful or spinless (or having full spin rotation symmetry) systems. I will show one realization in photonic crystals in...

### Condensed Matter Seminar, Chen Fang, MIT, "TBA"

### Special CM Seminar, Shuichi Murakami, Tokyo Inst., "Topological semimetals and chiral transport in inversion asymmetric systems"

Thu, Oct 29, 2015, 3:00 pm to 4:15 pm

The Z2 topological insulators (TIs) are topological phases under time-reversal symmetry. In 2007, we theoretically proposed a universal phase diagram describing a phase transition between 3D TIs and normal insulators (NIs), and we showed that in a TI-NI transition, a Weyl semimetal phase necessarily intervenes between the two phases, when...

### CM Seminar, Avraham Klein, Hebrew University of Jerusalem, "Vortex core deformation in weakly coupled superfluids"

Tue, Oct 27, 2015, 1:15 pm to 2:30 pm

Quantum vortices in weakly coupled superfluids have a large healing length, so that many particles reside within the vortex core. They are characterized by topologically protected singular points, which in principal should keep their core structure rigid.

### Condensed Matter Seminar, Paul Fendley, Oxford, " Strong Zero Modes and Eigenstate Phase Transitions"

Mon, Oct 26, 2015, 1:15 pm to 2:30 pm

Gapless edge or zero modes surviving the presence of disorder are common in a topological phase of matter.

### EE/CMS, Kevin Slagle, UCSB, "Exotic quantum phase transitions of 2+1d Dirac fermions, "

Mon, Oct 19, 2015, 1:30 pm to 2:30 pm

Using determinant quantum Monte Carlo simulations, we demonstrate that an extended Hubbard model on a bilayer honeycomb lattice has two novel quantum phase transitions, each with connections to symmetry protected topological states (SPT).

### Special Condensed Matter Seminar, Roman Orus, Mainz, “Entanglement, tensor networks, and topological quantum order”

Wed, Oct 14, 2015, 1:15 pm to 2:15 pm

Topological order in a 2d quantum matter can be determined by the topological contribution to the entanglement Renyi entropies. However, when close to a quantum phase transition, its calculation becomes cumbersome.

### Condensed Matter Seminar, Roger Mong, U Pittsburgh, "Fibonacci anyons and charge density order in the 12/5 and 13/5 quantum Hall plateaus"

Mon, Oct 12, 2015, 1:15 pm to 2:30 pm

The ν = 12/5 fractional quantum Hall plateau observed in GaAs wells is a suspect in the search for non-Abelian Fibonacci anyons. Fibonacci anyons are special i

### Special CM Seminar, Yuval Baum, Weizmann Institute, "Current at a distance and resonant transparency in Weyl semi-metals"

Thu, Oct 1, 2015, 3:00 pm to 4:30 pm

Topology in various guises plays a central role in modern condensed matter physics. Although the
original applications of topological ideas to band structures relied on the existence of a fully gapped
bulk spectrum, more recently it has been recognized that protected surface states can arise even in

### Special CM Seminar, Liling Sun, Chinese Academy, "Findings and phenomena in Fe-based superconductors ..."

Wed, Sep 23, 2015, 2:00 pm to 3:00 pm

It has been established that the superconductivity of unconventional superconductors is dictated by their crystallographic structure, electronic charge, and orbital and spin degrees of freedom, which can all be manipulated by controlling parameters such as pressure, magnetic field and chemical composition.

### Condensed Matter Seminar, Arun Paramekanti, U. of Toronto, "Double perovskites - magnetism, topology, and topological transitions."

Mon, Sep 21, 2015, 1:00 pm to 2:15 pm

Double perovskites are of great interest, providing us with material examples of metallic high Tc ferro-magnets, Mott insulating ferromagnets, as well as geometrically frustrated magnets on the fcc lattice.

### Special Condensed Matter Seminar, Carlos Sa De Melo, Georgia Tech, "Effects of spin-orbit coupling on the Berezinskii-Kosterlitz-Thouless ..."

Wed, May 20, 2015, 1:15 pm to 2:30 pm

We investigate the Berezinskii-Kosterlitz-Thouless (BKT) transition in a two-dimensional (2D) Fermi gas with spin-orbit coupling (SOC), as a function of the two-body binding energy and a perpendicular Zeeman field [1].

### Condensed Matter Seminar, Inna Vishik, MIT, "Ultrafast dynamics in heavy fermions and electron-doped cuprates"

Mon, May 4, 2015, 1:15 pm to 2:30 pm

Ultrafast (sub-picosecond) spectrosopies have emerged as important tools for studying quantum materials, and one of the strengths of time-domain experiments is that they can distinguish coexisting phases via their distinct recovery dynamics.

### Condensed Matter Seminar, Joel Moore, UC, Berkeley, "Dynamical consequences of non-Abelian gauge fields and non-Abelian particles in solids"

Mon, Apr 20, 2015, 1:15 pm to 2:30 pm

An electron moving through a crystal ceases to be a featureless point particle and acquires structure within the unit cell, with far-reaching consequences.