Low Energy Challenges for High Energy Physicists II

Conference Date:
Monday, August 22, 2016 (All day) to Friday, August 26, 2016 (All day)
Scientific Areas:
Condensed Matter
Quantum Fields and Strings

Throughout the history of quantum field theory there has been a rich cross-pollination between high energy and condensed matter physics. From the theory of renormalization to the consequences of spontaneous symmetry breaking this interaction has been an incredible fruitful one. In the last decade there has been a strong resurgence of interest in condensed matter systems in the high energy theoretical physics community. With developments in conformal field theories, AdS/CFT, and effective field theory techniques high energy theorists with all kinds of specialist backgrounds are thinking about the diverse behavior exhibited in low energy physical systems. In addition to these general tools, and their accompanying diverse set of applications, an additional major theme for the conference will be hydrodynamic behavior in condensed matter systems. Recently there has been intense theoretical investigation of hydrodynamics general formulation and fundamental bounds on transport coefficients. These efforts have been made all the more relevant with possible realization of hydrodynamic transport in low energy systems such as metals and graphene. Building on the success of the 2014 edition of this workshop, we propose to reinvigorate once again this fruitful collaboration by bringing together like-minded high energy theorists with appropriate condensed-matter theorists and experimentalists to tackle some of the most interesting problems in modern physics.

Registration for this workshop is now closed.

• Michael Blake, Massachusetts Institute of Technology
• Kin Chung Fong, Raytheon BBN, Harvard
• Sera Cremonini, Lehigh University
• Blaise Gouteraux, Stanford University & APC, CNRS Paris
• Diego Hofman, University of Amsterdam
• Leonid Levitov, Massachusetts Institute of Technology
• Hong Liu, Massachusetts Institute of Technology
• Andrew Lucas, Stanford University
• Joseph Maciejko, University of Alberta
• Andrew Mackenzie, Max Planck Institute
• John McGreevy, University of California, San Diego
• Jeffrey Murugan, Institute for Advanced Study
• Alberto Nicolis, Columbia University
• David Poland, Yale University
• Marco Polini, Instituto Italiano de Technolgia
• Subir SachdevPerimeter Institute & Harvard University
• Kai Sun, University of Michigan
• Martin Zwierlein, Massachusetts Institute of Technology
• Lasma Alberte, SISSA
• Matteo Baggioli, Universitat Autonoma de Barcelona
• Yoni BenTov, California Institute of Technology
• Michael Blake, Massachusetts Institute of Technology
• Alex Buchel, Perimeter Institute
• Andres Carvajal, Perimeter Institute
• Sera Cremonini, Lehigh University
• Richard Davison, Harvard University
• Luca Delacretaz, Stanford University
• Nima Doroud, University of Cambridge
• Sergei Dubovsky, Perimeter Institute
• Solomon Endlich, Stanford University
• Angelo Esposito, Columbia University
• Kin Chung Fong, Raytheon BBN, Harvard
• Blaise Gouteraux, Stanford University & APC, CNRS Paris
• Sean Hartnoll, Stanford University
• Kurt Hinterbichler, Perimeter Institute
• Diego Hofman, University of Amsterdam
• Bart Horn, University of Texas at Austin
• Anna Karlsson, Stanford University
• David Kubiznak, Perimeter Institute
• Leonid Levitov, Massachusetts Institute of Technology
• Hong Liu, Massachusetts Institute of Technology
• Andrew Lucas, Stanford University
• Joseph Maciejko, University of Alberta
• Andrew Mackenzie, Max Planck Institute
• Dalimil Mazac, Perimeter Institute
• John McGreevy, University of California, San Diego
• Alexander Monin, École Polytechnique Fédérale de Lausanne
• Jeffrey Murugan, Institute for Advanced Study
• Alberto Nicolis, Columbia University
• Riccardo Penco, Columbia University
• Federico Piazza, CPT, Universite' Aix-Marseille
• David Poland, Yale University
• Marco Polini, Instituto Italiano de Technolgia
• Srinivas Raghu, Stanford University
• Ira Rothstein, Carnegie Mellon University
• Subir Sachdev, Perimeter Institute & Harvard University
• Vasudev Shyam, Perimeter Institute
• Julia Steinberg, Harvard University
• Kai Sun, University of Michigan
• Chenjie Wang, Perimeter Institute
• Amanda Weltman, University of Cape Town
• Shuo Yang, Perimeter Institute
• Jiecheng Zhang, Stanford University
• Martin Zwierlein, Massachusetts Institute of Technology

Monday, August 22, 2016

 Time Event Location 9:00 – 9:30am Registration Reception 9:30 – 10:30am Alberto Nicolis, Columbia UniversityTBA Bob Room 10:30 – 11:15am Coffee Break Bistro – 1st Floor 11:15 – 12:15pm Martin Zwierlein, Massachusetts Institute of TechnologySolitons and Spin-Charge Correlations in Strongly Interacting Fermi Gases Bob Room 12:15 – 2:15pm Lunch Bistro – 1st Floor 2:15 – 3:15pm John McGreevy, University of California, San DiegoHierarchical growth of entangled states Bob Room 3:15 – 4:00pm Coffee Break Bistro – 1st Floor 4:00 – 5:00pm Sera Cremonini, Lehigh UniversityScaling geometries and DC conductivities Bob Room

Tuesday, August 23, 2016

 Time Event Location 9:30 – 10:30am Leonid Levitov, Massachusetts Institute of TechnologyViscous Electron Fluids: Higher-Than-Ballistic Conduction Negative Nonlocal Resistance and Vortices Bob Room 10:30 – 11:15am Coffee Break Bistro – 1st Floor 11:15 – 12:15pm Kin Chung Fong, Raytheon BBN, Harvard UniversityTBA Bob Room 12:15 – 2:15pm Lunch Bistro – 1st Floor 2:15 – 3:15pm Michael Blake, Massachusetts Institute of TechnologyUniversal Diffusion and the Butterfly Effect Bob Room 3:15 – 4:00pm Coffee Break Bistro – 1st Floor 4:00 – 5:00pm Jeff Murugan, Institute for Advanced StudyParticle-Vortex duality and Topological Quantum Matter Bob Room

Wednesday, August 24, 2016

 Time Event Location 9:30 – 10:30am Andrew Mackenzie, Max Planck InstituteTBA Bob Room 10:30 – 11:15am Coffee Break Bistro – 1st Floor 11:15 – 12:15pm Student Talks  Luca Delacretaz, Stanford UniversityHydrodynamic theory of fluctuating stripes Angelo Esposito, Columbia UniversityFirst sound of zero temperature holographic superfluids Matteo Baggioli, Universitat Autonoma de BarcelonaJogging Through Holographic Massive Gravity Bob Room 12:15 – 2:15pm Lunch Bistro – 1st Floor 2:15 – 3:15pm Joseph Maciejko, University of AlbertaSuperconducting quantum criticality of Dirac fermions Bob Room 3:15 - 3:20pm Conference Photo TBA 3:20 – 4:00pm Coffee Break Bistro – 1st Floor 4:00 – 5:00pm Andrew Lucas, Stanford UniversityHydrodynamic theory of transport in Dirac and Weyl semimetals Bob Room

Thursday, August 25, 2016

 9:30 – 10:30am Subir Sachdev, Harvard UniversityTheories of non-Fermi liquids Bob Room 10:30 – 11:15am Coffee Break Bistro – 1st Floor 11:15 – 12:15pm Marco Polini, Instituto Italiano de TechnolgiaHydrodynamic electron transport in a graphene field effect transistor Bob Room 12:15 – 2:15pm Lunch Bistro – 1st Floor 2:15 – 3:15pm Hong Liu, Massachusetts Institute of TechnologyEffective field theory of dissipative fluids Bob Room 3:15 – 4:00pm Coffee Break Bistro – 1st Floor 4:00 – 5:00pm Diego Hofman, University AmsterdamGeneralized Global Symmetries and Magnetohydrodynamics Bob Room 6:00pm Banquet Delta

Friday, August 26, 2016

 9:30 – 10:30am Blaise Gouteraux, Stanford University & APC, CNRS ParisHydrodynamic theory of quantum fluctuating superconductivity Bob Room 10:30 – 11:00am Coffee Break Bistro – 1st Floor 11:00 – 12:00pm Kai Sun, University of MichiganUniversal features of Lifshitz Green’s functions -- from holography and field theory Bob Room 12:00 – 1:30pm Lunch Bistro – 1st Floor 1:30 – 2:30pm David Poland, Yale UniversityBootstrapping 3D CFTs Bob Room 2:30 – 2:40pm Closing Remarks Bob Room

Matteo Baggioli, Universitat Autonoma de Barcelona

Jogging Through Holographic Massive Gravity

We present some recent developments in the framework of holographic (Lorentz violating) massive gravity.
We rigorously define the most generic isotropic setup in 3+1 dimensions and we study in detail its phenomenology.
We describe the electric and the viscoelastic responses of the system and we comment on the fate of the KSS viscosity bound in absence of translational symmetry. We conclude with some discussion hints and comments for the future.

Michael Blake, Massachusetts Institute of Technology

Universal Diffusion and the Butterfly Effect

In 2014 Hartnoll proposed that the diffusion constants of incoherent metals should be bounded as $D \geq \hbar v^2/ (k_B T)$, where v is a characteristic velocity. In this talk I will describe a large class of holographic theories that saturate such a bound, with $v$ being the velocity of the butterfly effect. Our results suggest a novel connection between transport at strong coupling and the field of quantum chaos.

Sera Cremonini, Lehigh University

Scaling geometries and DC conductivities

Non-relativistic geometries that violate hyperscaling have been used as holographic laboratories for probing strongly coupled  phases with anomalous scalings. In this talk I will discuss holographic computations of DC conductivities in gravitational systems that exhibit such scalings, and  allow for momentum dissipation.  I will also comment on the cases in which one obtains a linear temperature dependence for the resistivity.

Luca Delacretaz, Stanford University

Hydrodynamic theory of fluctuating stripes

I will present a hydrodynamic description of matter in a charge density wave (or "smectic") phase. As in superfluids, the spontaneous breaking of a continuous symmetry -- here translations in one direction -- adds a Goldstone phase to the usual long lived hydrodynamic variables. This phase propagates as a highly anisotropic "second sound" mode at low energies, affecting properties such as transport. Phase fluctuations, due to proliferating dislocations, give a finite life-time to certain collective modes, which can be experimentally probed e.g. by measuring ultrasound attenuation. Using the memory matrix, the hydrodynamic approach predicts sound attenuation to be proportional to the shear viscosity of the normal (non-smectic) state.

Angelo Esposito, Columbia University

First sound of zero temperature holographic superfluids

Within the context of AdS/CFT, the gravity dual of an s-wave superfluid is given by scalar QED on an asymptotically AdS spacetime. While this conclusion is vastly based on numerical arguments, I will provide an analytical proof that this is indeed the case. In particular, I will present a technique which allows to explicitely compute the low-energy effective action for the boundary theory starting from the bulk system. This will be done for an arbitrary number of dimensions and an arbitrary potential. I will recover the known dispersion relation for conformal first sound.

Blaise Gouteraux, Stanford University & APC, CNRS Paris

Hydrodynamic theory of quantum fluctuating superconductivity

A hydrodynamic theory of transport in quantum mechanically phase-disordered superconductors is possible when supercurrent relaxation can be treated as a slow process. We obtain general results for the frequency-dependent conductivity of such a regime. With time-reversal invariance, the conductivity is characterized by a Drude-like peak, with width given by the supercurrent relaxation rate. Using the memory matrix formalism, we obtain a formula for this width (and hence also the dc resistivity) when the supercurrent is relaxed by short range Coulomb interactions. This leads to a new -- effective field theoretic and fully quantum -- derivation of a classic result on flux flow resistance. With strong breaking of time-reversal invariance, the optical conductivity exhibits what we call a hydrodynamic supercyclotron' resonance. We obtain the frequency and decay rate of this resonance for the case of supercurrent relaxation due to an emergent Chern-Simons gauge field. The supercurrent decay rate in this topologically ordered superfluid vortex liquid' is determined by the conductivities of the normal component of the liquid. Our work gives a controlled framework for low temperature metallic phases arising from phase-disordered superconductivity.

Diego Hofman, University of Amsterdam

Generalized Global Symmetries and Magnetohydrodynamics

I will discuss a global symmetry approach to constructing the most general effective field theory of magnetohydrodynamics.

Leonid Levitov, Massachusetts Institute of Technology

Viscous Electron Fluids: Higher-Than-Ballistic Conduction Negative Nonlocal Resistance and Vortices

Hong Liu, Massachusetts Institute of Technology

Effective field theory of dissipative fluids

Andrew Lucas, Stanford University

Hydrodynamic theory of transport in Dirac and Weyl semimetals

I will discuss recent progress in understanding the consequences of hydrodynamic electron flow on measurable transport properties of metals, focusing on metals where the electrons behave as a charge neutral relativistic plasma.  In graphene, I will connect our theoretical models with experimental data and show how we can explain features of transport in graphene that are inconsistent with quasiparticle transport.   I will then discuss the extension of these results to Weyl semimetals, which are modeled by a system of multiple chiral fluids.   Negative magnetoresistance can occur in both electric and thermal transport; the latter is a consequence of a distinct axial-gravitational anomaly.   Future transport experiments on Weyl semimetals can discover this exotic type of anomaly in the lab.

Joseph Maciejko, University of Alberta

Superconducting quantum criticality of Dirac fermions

The semimetal-superconductor quantum phase transition of 2D Dirac fermions, such as found on the surface of a topological insulator, is conjectured to exhibit an emergent N=2 supersymmetry, based on a one-loop renormalization group analysis. In this talk I will present further evidence for this conjecture based on a three-loop analysis. Assuming the conjecture is true, I will present exact results for certain critical properties including the optical conductivity, shear viscosity, and entanglement entropy at zero temperature, as well as the finite-temperature optical conductivity.

John McGreevy, University of California, San Diego

Hierarchical growth of entangled states

This talk, based on work with Brian Swingle, will describe the s-sourcery program.
Its goal is to extend the lessons of the renormalization group to quantum many body states.

Jeffrey Murugan, Institute for Advanced Study

Particle-Vortex duality and Topological Quantum Matter

David Poland, Yale University

Bootstrapping 3D CFTs

I will review recent results from applying the conformal bootstrap to 3D CFTs, including precise determinations of critical exponents and in the 3D Ising and O(N) vector models, new constraints on 3D Gross-Neveu models, and general bounds on correlation function coefficients of currents and stress tensors.

Marco Polini, Instituto Italiano de Technolgia

Hydrodynamic electron transport in a graphene field effect transistor

Graphene sheets encapsulated between crystals of hexagonal boron nitride host a unique two-dimensional (2D) electron system, whereby electrons suffer minimal scattering against acoustic phonons and practically no scattering against long-range disorder (unless gated very close to the charge neutrality point) [1-4]. Above liquid nitrogen temperatures, these electron liquids are expected to display local equilibrium enabled by strong electron-electron interactions [5,6] and viscosity-dominated hydrodynamic transport.

In this talk I will report on results of combined theoretical and experimental work [7,8] showing unambiguous evidence for this long-sought transport regime. In particular, I will discuss how high-quality doped graphene sheets above liquid nitrogen temperatures exhibit negative non-local resistance near current injection points and whirlpools in the spatial current pattern. Measurements of these non-local electrical signals enable to extract the value of the kinematic viscosity of the two-dimensional massless Dirac fermion liquid in graphene, which is found to compare well with many-body theoretical predictions [6]. If time allows, I will also discuss the subtle connection between negative non-local resistances and current whirlpools [9].

References
[1] A.S. Mayorov et al., Nano Lett. 11, 2396 (2011).
[2] L. Wang et al., Science 342, 614 (2013).
[3] T. Taychatanapat et al., Nature Phys. 9, 225 (2013).
[4] A. Woessner et al., Nature Mater. 14, 421 (2015).
[5] M. Polini and G. Vignale, The quasiparticle lifetime in a doped graphene sheet.  In No-nonsense physicist: an overview of Gabriele Giuliani's work and life (eds. M. Polini, G. Vignale, V. Pellegrini, and J.K. Jain) (Edizioni della Normale, Pisa, 2016).
[6] A. Principi, G. Vignale, M. Carrega, and M. Polini, Phys. Rev. B 93, 125410 (2016).
[7] I. Torre, A. Tomadin, A.K. Geim, and M. Polini, Phys. Rev. B 92, 165433 (2015).
[8] D. Bandurin, I. Torre, R.K. Kumar, M. Ben Shalom, A. Tomadin, A. Principi, G.H. Auton, E. Khestanova, K.S. NovoseIov, I.V. Grigorieva, L.A. Ponomarenko, A.K. Geim, and M. Polini, Science 351, 1055 (2016).
[9] F.M.D. Pellegrino, I. Torre, A.K. Geim, and M. Polini, arXiv:1607.03726 (2016).

Subir Sachdev, Harvard University & Perimeter Institute

Theories of non-Fermi liquids

I will review and compare numerous models for metallic states without
quasiparticle excitations. The solvable SYK model provides a useful starting point,
and also has remarkable holographic connections to the quantum gravity
of black holes in AdS2. Quantum critical states of two-dimensional metals
are obtained by coupling the fermions to fluctuating bosonic order parameters
or gauge fields: I will discuss their physical properties and possible connections
to experiments.

Kai Sun, University of Michigan

Universal features of Lifshitz Green’s functions--- from holography and field theory

In this talk, we examine the behavior of the retarded Green’s function in theories with Lifshitz scaling symmetry, both through dual gravitational models and a direct field theory approach. In contrast with the case of a relativistic CFT, where the Green’s function is fixed (up to normalization) by symmetry, the generic Lifshitz Green’s function can a priori depend on an arbitrary function Nevertheless, we demonstrate that the imaginary part of the retarded Green’s function (i.e. the spectral function) of scalar operators is exponentially suppressed in a window of frequencies near zero. This behavior is universal in all Lifshitz theories without additional constraining symmetries. On the gravity side, this result is robust against higher derivative corrections, while on the field theory side we present two z>1 examples where the exponential suppression arises from summing the perturbative expansion to infinite order, as a consequence of the energy-momentum conservation.

Martin Zwierlein, Massachusetts Institute of Technology

Solitons and Spin-Charge Correlations in Strongly Interacting Fermi Gases

Ultracold atomic Fermi gases near Feshbach resonances or in optical lattices realize paradigmatic, strongly interacting forms of fermionic matter. Topological excitations and spin-charge correlations can be directly imaged in real time. In resonant fermionic superfluids, we observe the cascade of solitonic excitations following a pi phase imprint. A planar soliton decays, via the snake instability, into vortex rings and long-lived solitonic vortices.
For fermions in optical lattices, realizing the Fermi-Hubbard model, we detect charge and antiferromagnetic spin correlations with single-site resolution. At low fillings, the Pauli and correlation hole is directly revealed. In the Mott insulating state, we observe strong doublon-hole correlations, which should play an important role for transport.

Closing Remarks

Friday Aug 26, 2016
Speaker(s):
Scientific Areas:

Bootstrapping 3D CFTs

Friday Aug 26, 2016
Speaker(s):

I will review recent results from applying the conformal bootstrap to 3D CFTs, including precise determinations of critical exponents and in the 3D Ising and O(N) vector models, new constraints on 3D Gross-Neveu models, and general bounds on correlation function coefficients of currents and stress tensors.

Scientific Areas:

Universal features of Lifshitz Green’s functions--- from holography and field theory

Friday Aug 26, 2016
Speaker(s):

In this talk, we examine the behavior of the retarded Green’s function in theories with Lifshitz scaling symmetry, both through dual gravitational models and a direct field theory approach. In contrast with the case of a relativistic CFT, where the Green’s function is fixed (up to normalization) by symmetry, the generic Lifshitz Green’s function can a priori depend on an arbitrary function Nevertheless, we demonstrate that the imaginary part of the retarded Green’s function (i.e. the spectral function) of scalar operators is exponentially suppressed in a window of frequencies near zero.

Scientific Areas:

Hydrodynamic theory of quantum fluctuating superconductivity

Friday Aug 26, 2016
Speaker(s):

A hydrodynamic theory of transport in quantum mechanically phase-disordered superconductors is possible when supercurrent relaxation can be treated as a slow process. We obtain general results for the frequency-dependent conductivity of such a regime. With time-reversal invariance, the conductivity is characterized by a Drude-like peak, with width given by the supercurrent relaxation rate. Using the memory matrix formalism, we obtain a formula for this width (and hence also the dc resistivity) when the supercurrent is relaxed by short range Coulomb interactions.

Scientific Areas:

Generalized Global Symmetries and Magnetohydrodynamics

Thursday Aug 25, 2016
Speaker(s):

I will discuss a global symmetry approach to constructing the most general effective field theory of magnetohydrodynamics.

Scientific Areas:

Effective field theory of dissipative fluids

Thursday Aug 25, 2016
Speaker(s):
Scientific Areas:

Hydrodynamic electron transport in a graphene field effect transistor

Thursday Aug 25, 2016
Speaker(s):
Scientific Areas:

Theories of non-Fermi liquids

Thursday Aug 25, 2016
Speaker(s):

I will review and compare numerous models for metallic states without
quasiparticle excitations. The solvable SYK model provides a useful starting point,
and also has remarkable holographic connections to the quantum gravity
of black holes in AdS2. Quantum critical states of two-dimensional metals
are obtained by coupling the fermions to fluctuating bosonic order parameters
or gauge fields: I will discuss their physical properties and possible connections
to experiments.

Scientific Areas:

Hydrodynamic theory of transport in Dirac and Weyl semimetals

Wednesday Aug 24, 2016
Speaker(s):

I will discuss recent progress in understanding the consequences of hydrodynamic electron flow on measurable transport properties of metals, focusing on metals where the electrons behave as a charge neutral relativistic plasma. In graphene, I will connect our theoretical models with experimental data and show how we can explain features of transport in graphene that are inconsistent with quasiparticle transport. I will then discuss the extension of these results to Weyl semimetals, which are modeled by a system of multiple chiral fluids.

Scientific Areas:

Superconducting quantum criticality of Dirac fermions

Wednesday Aug 24, 2016
Speaker(s):

The semimetal-superconductor quantum phase transition of 2D Dirac fermions, such as found on the surface of a topological insulator, is conjectured to exhibit an emergent N=2 supersymmetry, based on a one-loop renormalization group analysis. In this talk I will present further evidence for this conjecture based on a three-loop analysis. Assuming the conjecture is true, I will present exact results for certain critical properties including the optical conductivity, shear viscosity, and entanglement entropy at zero temperature, as well as the finite-temperature optical conductivity.

Scientific Areas:

Pages

Scientific Organizers:

• Solomon Endlich, Stanford University
• Sean Hartnoll, Stanford University
• Kurt Hinterbichler, Perimeter Institute
• Alberto Nicolis, Columbia University
• Riccardo Penco, Columbia University