Bela Bauer (Microsoft Station Q) 
Gapped and gapless spin liquid phases on the Kagome lattice from chiral threespin interactions


We examine a relatively simple SU(2)invariant model containing chiral threespin interactions on a Kagome lattice of S=1/2 spins, and show that it can give rise to both a gapped topological and a gapless quantum spin liquid. The model can be obtained from a Hubbard model, where fluxes through the elementary triangles of the lattice give rise to the chiral spin term. Our arguments are rooted in a formulation in terms of network models of edge states and are backed up by a careful numerical analysis. For a uniform choice of chirality on the lattice, we realize the KalmeyerLaughlin state, i.e. a gapped topological spin liquid which is identified as the nu=1/2 bosonic Laughlin state. We numerically obtain a full characterization of the universal properties of the state, including the topological degeneracy, the gapless edge state and the anyonic bulk excitations. For staggered chiralities, a gapless spin liquid emerges which exhibits gapless spin excitations along lines in momentum space, a feature that we probe by studying quasitwodimensional systems of finite width. We thus provide a single, appealingly simple spin model (i) for what is probably the simplest realization of the KalmeyerLaughlin state to date, as well as (ii) for a nonFermi...


Jennifer Cano (University of California Santa Barbara) 
Bulkedge correspondence in 2+1dimensional Abelian topological phases


The same bulk twodimensional topological phase can have multiple distinct, fullychiral edge phases. We show that this can occur in the integer quantum Hall states at $\\nu=8$ and $12$, with experimentallytestable consequences. We show that this can occur in Abelian fractional quantum Hall states as well, with the simplest examples being at $\\nu=8/7, 12/11, 8/15, 16/5$. We give a general criterion for the existence of multiple distinct chiral edge phases for the same bulk phase and discuss experimental consequences. Edge phases correspond to lattices while bulk phases correspond to genera of lattices. Since there are typically multiple lattices in a genus, the bulkedge correspondence is typically onetomany; there ...


Anushya Chandran (Perimeter Institute) 
Stringnet coarsening in topologically ordered systems


We consider the nonequilibrium dynamics of topologically ordered systems driven across a continuous phase transition into proximate phases with no, or reduced, topological order. This dynamics exhibits scaling in the spirit of Kibble and Zurek but now {\\it without} the presence of symmetry breaking and a local order parameter. The late stages of the process are seen to exhibit a slow, coarsening dynamics for the stringnet that underlies the physics of the topological phase, a potentially interesting signature of topological order. We illustrate these phenomena in the context of particular phase transitions out of the abelian Z_2 topologically ordered phase of the toric code/Z_2 gauge theory, and the nonabelian SU(2)k ordered phases of the relevant LevinWen models.


Ru Chen (University of California, Santa Barbara) 
Quadratic band touching, magnetism and the metalinsulator transition in pyrochlore iridates.


The study of 4d and 5d transition metal oxides is interesting because these materials incorporate both strong spinorbit coupling and strong correlations, and consequently distinct physical properties and the tantalizing possibility of novel topological phases. The ab initio results show that Pr$_2$Ir$_2$O$_7$ is a strong candidate to the ideal LuttingerAbrikosovBenesvilavskii state, which has a quadratic band touching right at the Fermi level. The sensitive feature of the quadratic band touching state suggests that strain/pressure applied to the pyrochlore iridate thin films may produce a topological insulator. The ab initio results also show systematic trend of stronger order and gap with decreasing rare earth radius. Comparison of the theoretical work with recent experimental results will also be discussed.


J. Patrick Clancy (University of Toronto)  
The pyrochore iridates A2Ir2O7 (A = Y or lanthanide) have been proposed to host a variety of exotic ground states driven by the interplay between electronic correlations and strong spinorbit coupling effects. This includes novel phases such as topological insulators, spin liquids, axion insulators, and Weyl semimetals. The identification of such phases often hinges on the measurement of the magnetic excitation spectrum or dynamic structure factor, usually carried out by inelastic neutron scattering (INS). However, in the case of the pyrochlore iridates, this presents a serious experimental challenge, as the large neutron absorption cross section of Ir and small size of available single crystal samples combine to make conventional INS measurements largely unfeasible. Resonant inelastic xray scattering (RIXS) represents a promising alternative to INS, which provides an elementspecific probe of elementary spin, charge, orbital, and lattice excitations. We have performed highresolution Ir L3edge RIXS measurements to investigate the characteristic excitation spectra of the pyrochlore iridates Eu2Ir2O7, Pr2Ir2O7, and Y2Ir2O7. These measurements reveal valuable information about both the magnetic excitations and ....


Plamadeala Eugeniu (University of California Santa Barbara) 
Distinct edge phases with the same bulk Abelian QuantumHall state


We show that fermionic systems can have edge phases with only bosonic lowenergy edge excitations, and we generalize the relation between bulk topological spins and the central charge. We demonstrate that every fermionic topological phase can be represented as a bosonic topogical phase together with some number of filled Landau levels. In addition, our analysis shows that every Abelian topological phase can be decomposed into a tensor product of theories associated with prime numbers p, such that the topological spins of quasiparticles in that theory are the p^nth roots of unity, for some n. This leads to a demonstration that all Abelian topological phases can be represented by U(1)^N ChernSimons theory with particular Kmatrices.


Hermann Freire (Federal University of Goiás, Brazil) 
Breakdown of Fermi liquid behavior near the hot spots in a twodimensional model: A twoloop ....


Motivated by a recent experimental observation of a nodal liquid on both single crystals and thin films of Bi2Sr2CaCu2O8+delta by Chatterjee et al. [Nature Physics 6, 99 (2010)], we perform a fieldtheoretical renormalization group (RG) analysis of a twodimensional model such that only eight points located near the hot spots on the Fermi surface are retained, which are directly connected by spin density wave ordering wavevector. We derive RG equations up to twoloop order describing the flow of renormalized couplings, quasiparticle weight, several orderparameter response functions, and uniform spin and charge susceptibilities of the model. We find that while several orderparameter susceptibilities investigated


Jim Garrison (University of California  Santa Barbara)  
We propose a novel quantum spin liquid state that can explain many of
the intriguing experimental properties of the lowtemperature phase of
the organic spin liquid candidate materials κ(BEDTTTF)2Cu2(CN)3 and
EtMe3Sb[Pd(dmit)2]2. This state of paired fermionic spinons preserves
all symmetries of the system, and it has a gapless excitation spectrum
with quadratic bands that touch at momentum k⃗=0. This quadratic band
touching is protected by symmetries. Using variational Monte Carlo
techniques, we show that this state has highly competitive energy in the
triangular lattice Heisenberg model supplemented with a realistically
large ringexchange term.


Pallab Goswami (National High Magnetic Field Laboratory) 
Topological properties of possible singlet chiral superconducting states for URu$_2$Si$_2$


We show that the current thermodynamic measurements in the superconducting phase of $\\mathrm{U}\\mathrm{Ru}_2\\mathrm{Si}_2$ are compatible with two distinct singlet chiral paired states $k_z(k_x \\pm i k_y)$ and $(k_x\\pm i k_y)^2$. Despite possessing similar low temperature thermodynamic properties, these two pairings are topologically distinguished by their respective orbital angular momentum projections along the caxis, $m=\\pm 1$ and $m=\\pm 2$. The point nodes of these states act as the monopoles and the antimonopoles of the Berry\'s gauge flux of charge $\\pm m$, which are separated in the momentum space along the $c$ axis. Consequently, the point nodes of $k_z(k_x+i k_y)$ and $(k_x \\pm ik_y)^2$ states respectively realize the Weyl and the doubleWeyl fermions, with chemical potential exactly tuned at the Fermi point, due to the charge conjugation symmetry. Due to the nontrivial topology, there are chirally dispersing surface states, which lead to Fermi arc, anomalous spin and thermal Hall effects, and various magnetoelectric effects. However, an unambiguous determination of the bulk invariant can only be achieved by probing the pairing symmetry via a corner Josephson junction measurement, and ...


Lai HsinHua (National High Magnetic Field Laboratory) 
Violation of EntanglementArea Law in Bosonic Systems with Bose surfaces: Possible Application to Bose Metals


We show the violation of the entanglementarea law for bosonic systems with gapless factorized energy dispersions on a N^d Cartesian lattice in ddimension, e.g., the exciton Bose liquid in two dimension. We explicitly show that a belt subsystem with width L preserving translational symmetry along d1 Cartesian axes has leading entanglement entropy (N^{d1}/3)\\\\ln L. Using this result, the strong subadditivity inequality, and lattice symmetries, we bound the entanglement entropy of a rectangular subsystem from below and above showing a logarithmic violation of the area law. For subsystems with a single flat boundary we also bound the entanglement entropy from below showing a logarithmic violation, and argue that the entanglement entropy of subsystems with arbitrary smooth boundaries are similarly bounded.


Mi Jiang (University of California Davis) 
NMR Knight shift anomaly in periodic Anderson model


We report a Determinant QMC investigation of the Knight
shift anomaly observed in NMR experiments of heavy
fermion materials. Knight shift is believed to
originate in the different temperature dependence of the conduction
electron and local moment components of the total susceptibility $\chi$.
We quantify the behavior of $\chi_{cc}(T), \chi_{cf}(T),$ and
$\chi_{ff}(T)$ in the framework of periodic Anderson model (PAM),
focusing on the evolution with different degree of conduction
electronlocal moment hybridization. These results confirm several
predictions of the twofluid theory of the Knight shift anomaly,
including the demonstration of a universal logarithmic divergence of the
contribution of the heavy electrons to the Knight shift. This universal
behavior, which occurs with decreasing temperature below $T^{\ast}$ in
the paramagnetic state, agrees well with experimental findings, and
indicates that different heavy fermion materials exhibit a common
scaling, differing only in the coherence temperature scale, $T^{\ast}$.


Dmitri Khveshchenko (University of North Carolina Chapel Hill) 
Searching for nonFermi liquids under holographic light


We identify physically relevant, albeit lying off the beaten track, gravity models that may provide a holographic description of some prototypical nonFermi liquid states of strongly correlated condensed matter systems. Specifically, we discuss prospective gravity duals of the ubiquitous models of nonrelativistic fermions coupled to gauge fields and Dirac fermions with the Coulomb interactions.


Andrei Kogan (University of Cincinnati) 
Transport spectroscopy of a Kondo singlet under a timedependent bias


We investigate the behavior of the Kondo singlet under a timedependent excitation using a SingleElectron transistor (SET) , a voltagecontrollable
electron trap realized via gating of twodimensional electron gas in a GaAs/AlGaAs heterostructure. We show that, at bias oscillation frequencies of
order of the Kondo temperature divided by Planck's constant, f0= kTk/h, the timeaveraged electron transport across the transistor becomes
nonadiabatic. At frequencies f ~ f0, the zerobias conductance of the SET exhibits a strong suppression as compared to adiabatic predictions, and
the suppression weakens when f is tuned both below and above f0. We find a good qualitative agreement between the observations and the available
theoretical predictions and suggest further experiments to further elucidate the role of the Kondo temperature as the universal dynamic energy scale.


Ryan Mishmash (University of California, Santa Barbara) 
A continuous Mott transition between a metal and a quantum spin liquid.


More than half a century after first being proposed by Sir Nevill Mott,
the deceptively simple question of whether the interactiondriven
electronic metalinsulator transition may be continuous remains enigmatic.
Recent experiments on twodimensional materials suggest that when the
insulator is a quantum spin liquid, lack of magnetic longrange order on
the insulating side may cause the transition to be continuous, or only
very weakly first order. Motivated by this, we examine an extended
Hubbard model on a triangular strip geometry that we argue harbors a
quantum phase transition between a metal and a gapless spin liquid
characterized by a spinon Fermi sea, i.e., the ``spin Bose metal''. We
solve this model using largescale numerical simulations, and present
evidence that the Mott transition is indeed continuous, of the
KosterlitzThouless type. These results may provide a rare insight into
the development of Mott criticality in strongly interacting
twodimensional materials, and elucidates a mechanism by which spinliquid
phases are stabilized in the vicinity of such transitions.


Shigeki Onoda (RIKEN) 
Quantumclassical crossover and Higgs confining transitions in quantum spin ice


We develop an analytical theory for treating thermal fluctuations in a compact U(1) lattice gauge theory for quantum spin ice. Starting from a U(1) quantum spin liquid ground state, thermal fluctuations of gauge fields reduce the length scale for the gaugefield coherence from an infinity at zero temperature to a finite value at finite temperatures. This produces a quantumclassical crossover when the gaugefield coherence length becomes compared to the thermal deBroglie length. Effects of thermal fluctuations on the zerotemperature transition from the U(1) quantum spinliquid to Higgs phase is also discussed. These results are compared to recent experimental findings from neutronscattering, muon spin relaxation, and thermodynamic measurements on magnetic rareearth (Yb, Pr, and Tb) pyrochlore oxides.


Khandker Quader (Kent State University) 
Physics near Pomeranchuk Instabilities in 3D Fermi Systems: A Tractable Crossing Symmetric ...


We explore physics of a 3D Fermi system near generalized Pomeranchuk instabilities using a tractable crossingsymmetric equation method. We investigate ferromagnetic, paramagnetic, and phase separation regions. We find that approach to one critical channel (spin or density) drives instabilities in other noncritical channels. We study causes and implications of this \"quantum multicriticality\". It is found that a charge nematic instability may precede spin or density Pomeranchuk instabilities under certain conditions. Interplay of spin and density quantum fluctuations and pairing trends in such systems are studied. The results should of general relevance, and may also be of relevance to ferromagnetic superconductors.


Armin Rahmani (Los Alamos National Laboratory)  
Strongly correlated fractional quantum Hall liquids support fractional excitations, which can be understood in terms of adiabatic flux insertion arguments. A second route to fractionalization is through the coupling of weakly interacting electrons to topologically nontrivial backgrounds such as in polyacetylene. Here we demonstrate that electronic fractionalization combining features of both these mechanisms occurs in noncoplanar itinerant magnetic systems, where integer quantum Hall physics arises from the coupling of electrons to the magnetic background. The topologically stable magnetic vortices in such systems carry fractional (in general irrational) electronic quantum numbers and exhibit Abelian anyonic statistics. We analyze the properties of these topological defects by mapping the distortions of the magnetic texture onto effective nonAbelian vector potentials. We support our analytical results with extensive numerical calculations.


Lucile Savary (University of California Santa Barbara) 
Excitations, order, and criticality in quantum pyrochlores


I will present our recent work on quantum criticality in the (conducting) pyrochlore iridates in the context of the wide range of exotic phenomena that occur on the pyrochlore lattice, such as Coulombic quantum spin liquids and quantum orderbydisorder. I will discuss in detail the physics of the highlyunusual superuniversal quantum critical point between a nonFermi liquid and a Weyl semimetal (with Isinglike order) that we uncovered in a model relevant to the pyrochlore iridates. There, the fluctuations in the parent nonFermi liquid phase compete with the fluctuations due to the coupling to the Ising order parameter. Remarkably, the fluctuations of both origins are of the same order of magnitude and the resulting quantum critical regime belongs to a unique, very large, universality class, genuinely different from those obtained by considering the effects of a single phenomenon. Moreover, the perturbative analysis is controlled, yielding better faith in the theory. I will describe the scaling laws and some unusual coefficients of many physical quantities, and provide a scheme to observe the quantum critical point in experiment. I will discuss further experimental consequences of our work, in particular in the context of Pr2Ir2O7, ...


Evelyn Tang (MIT) 
Superconductor with intrinsic topological order in a flat band system


Recently, it has been shown that in certain lattice systems, e.g. in a flat band with spinorbit coupling and spin polarization, at commensurate fillings the ground state is a fractional quantum Hall state. The excitations of this state are anyons, and we explore what happens at incommensurate fillings, where doping the system is assumed to create a finite density of anyon excitations. The presence of the underlying lattice allows access to an entirely new regime where the anyon kinetic energy can be larger than the anyon interaction strength. This leads to an anyon gas which can condense to form a charged superfluid. Driven by repulsive interactions, this mechanism for superconductivity differs from the conventional one of electron pairing. We present three possible outcomes, the first two with intrinsic topological order, i.e. containing fractionalized quasiparticles; while the third has no fractionalized excitations similar to a BCStype state.


Yuya Tanizaki (The University of Tokyo and RIKEN) 
Functional Renormalization Group Method for BEC of Composite Particles


In this decade, experimental development of cold atomic systems has stimulated theoretical study of
superfluidity. For the twocomponent fermionic system with the strong attractive interaction between fermions,
the normal phase shows pseudogap and the Fermiliquid picture does not apply. In order to study such
nonperturbative physics, we developed a new formalism of FRG. We show that our formalism can describe the BEC
of composite bosons in terms of the original fermionic degrees of freedom in the deep BEC region of the BCSBEC crossover.


Chong Wang (Massachusetts Institute of Technology)  
We propose a new theoretical scheme to obtain novel gapless states in frustrated spin/boson systems by fractionalizing topological defects. We focus on 2D systems with global $U(1)$ symmetries (bosons or XYspins), in which we fractionalize the vortices into gapless fermions. We give an example of such a scheme and interpret it as a critical phase in the
vicinity of spinnematic states. An explicit construction is given in an $XY$spin1 system on triangular lattice.


Peng Ye (Perimeter Institute for Theoretical Physics) 
Constructing symmetric topological phases via fermionic projective construction and dyon condensation


Recently, there is a considerable study on gapped symmetric phases of bosons that do not break any symmetry. Even without symmetry breaking, the bosons can still be in many exotic new states of matter, such as symmetryprotected trivial (SPT) phases which are shortrange entangled and symmetryenriched topological (SET) phases which are longrange entangled. It is wellknown that \\emph{noninteracting fermionic topological insulators}....


Hao Zhihao (University of Waterloo) 
Unconventional quantum critical point in a quantum dimer model on the kagome lattice


We study the minimum quantum dimer model on the kagome lattice using zero
temperature Green's function Monte Carlo method. In the "extreme quantum
limit", the model hosts a large dimer liquid phase adjacent to two valence
bond solid phases (VBS). The phase transition to one of the VBS is
continuous, induced by vison condensation. The critical theory contains
four real fields, predicted by a projective symmetry analysis. The
critical point is likely controlled by a new universality class beyond the
standard Landau theory of phase transition.


Zheng Zhu ( Institute for Advanced Study, Tsinghua University, Beijing)  
The fate of a hole injected in an antiferromagnet is an outstanding issue of strongly correlated physics. It provides important insights into doped Mott insulators closely related to hightemperature superconductivity. Here, we report a systematic numerical study of tJ ladder systems based on the density matrix renormalization group. It reveals a surprising result for the single hole’s motion in an otherwise wellunderstood undoped system. Specifically, we find that the common belief of quasiparticle picture is invalidated by the selflocalization of the doped hole. In contrast to Anderson localization caused by disorders, the charge localization discovered here is an entirely new phenomenon purely of strong correlation origin. It results from destructive quantum interference of novel signs picked up by the hole, and since the same effect is of a generic feature of doped Mott physics, our findings unveil a new paradigm which may go beyond the single hole doped system.
