Recent advances in preparing, probing and manipulating ultracold atomic gases enable studying condensed matter physics in a very controlled setting. In the first part of my talk, I will describe quantum gas microscopy, a powerful tool for imaging and manipulating strongly interacting quantum gases containing thousands of atoms at the single atom…

In this talk I will review recent theoretical work on a new class of topological material systems - topological Kondo insulators, which appear as a result of interplay between strong correlations and spin-orbit interactions. I will start with introducing the by now standard theory of topological band insulators and explain the Fu-Kane method to…

Using a controlled weak-coupling renormalization group approach, we establish the mechanism of unconventional superconductivity in the vicinity of spin or charge ordered excitonic states for the case of electrons on the Bernal stacked bilayer honeycomb lattice. With one electron per site this system exhibits nearly parabolically touching…

Abstacts not available for these talks.

The recently discovered topological crystalline insulators harbor Dirac surface states protected by a discrete set of crystalline space group symmetries and show immense promise for novel quantum applications. In this talk, I will present a first principles investigation as well as a model Hamiltonian of the nontrivial surface states and their…

Since the discovery that electrons in graphene behave as massless Dirac fermions, the single-atom-thick material has become a fertile playground for testing exotic predictions of quantum electrodynamics, such as Klein tunneling and the fractional quantum Hall effect. Now add to that list atomic collapse, the spontaneous formation of electrons and…

Quantum point contacts (QPCs) are the basic building blocks of any mesoscopic structure, and display quantized conductance, reflecting the quantization of the number of transparent channels. An additional feature, coined the "0.7 anomaly", has been observed in almost all QPCs, and has been a subject of intensive debate in the last couple of…

Angle-resolved photoemission spectroscopy (ARPES) has been used extensively in studying electronic structure and superconducting gap of the iron-based superconductors (IBSCs). In this talk, I will present our ARPES results on the IBSCs, mainly focus on high-resolution measurements of the superconducting gap of many different IBSCs. Our results…

In this talk, I will propose that the mix valence phenomena in some of the rare earth compounds will naturally lead to non-trivial topology in band structure.One of the typical example is SmB6, where the intermediate valence of Sm generates band inversion at the X point and the non-trivial Z2 index. Other than SmB6, YbB6 and YbB12 are both…

Progress on solid state qubits, particularly Josephson junction devices, now brings us to the possibility of planning a scalable, multi-qubit architecture.  While we can envision how the quantum part of device can be designed to effectively implement fault tolerant error correction, I will argue that, if implemented with present-day techniques,…

Structure and symmetry play important roles in determining electronic properties of periodic solids. The interplay between crystalline symmetry and electronic topology leads to new phases of matter dubbed topological crystalline insulators, which possess protected surface states with unique and tunable electronic properties. In this talk, I…

Chen Fang will discuss Crystalline Topological Insulators SuYang Xu will discuss Protected & Broken Symmetries in TIs

In the last few decades, various puzzles have emerged in the study of strongly-correlated materials. In a family of strongly-correlated insulators, known as Kondo insulators, one such long-standing puzzle has remained open for over 40 years. In particular, it has been found that some Kondo insulators display strange electrical transport that…

Electronic confinement at nanoscale dimensions remains a central means of science and technology. I will describe a novel method for producing electronic nanostructures at the interface between two normally insulating oxides, LaAlO3 and SrTiO3. These structures and devices are “written” by a conductive atomic force microscope probe in ambient…

A spin liquid is a hypothetical quantum ground state of a frustrated Heisenberg magnet conjectured by P.W. Anderson in the 1970s. Its distinguishing features are (1) a lack of magnetic order and (2) a degeneracy that depends on the topology of the system. The status of spin liquids has been recently upgraded from purely speculative to plausible…

I will describe experimental studies of new states of magnetism on the S=1/2 kagomé lattice. In particular, I will discuss results on two materials: one with antiferromagnetic exchange (herbertsmithite) and one with ferromagnetic exchange (Cu(1,3-bdc)). Quantum spin liquids are new states of matter that are characterized by long-range…

Electrons moving in a periodic electric potential form Bloch energy bands where the mass of electrons are effectively changed. In a strong magnetic field, the cyclotron orbits of free electrons are quantized and Landau levels forms with a massive degeneracy within. In 1976, Hofstadter showed that for 2-dimensional electronic system, the…

In this talk I will describe our experimental investigations of an AlGaAs/GaAs based triple quantum dot circuit and their comparison with theoretical models. We are able to employ both quantum transport and charge detection down to single electron/spin occupation and employ many of the pulsing techniques developed previously for two dot circuits…

We show that the framework of condensate-induced transitions between two-dimensional topological phases can be used to relate one-dimensional spin models at their critical points. To illustrate this, we show that two well-known spin chains, namely the XY chain and the transverse field Ising chain with only next-nearest-neighbor interactions,…