Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session W64: NonFermi Liquid TheoryRecordings Available

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Sponsoring Units: DCMP Chair: Shouvik Sur, Rice University Room: Hyatt Regency Hotel Grant Park B 
Thursday, March 17, 2022 3:00PM  3:12PM 
W64.00001: Effective Field Theory for Fermi Liquids and nonFermi liquids Luca V Delacretaz, YiHsien Du, Umang B Mehta, Dam T Son I will show how to construct an effective field theory describing the bosonic sector of Fermi liquids. While at the linear level, the theory is equivalent to multidimensional bosonization, it necessarily features nonlinear corrections that are fixed by symmetry. These are crucial to reproduce nonlinear response and certain other aspects of Fermi liquid theory phenomenology that are not captured by current bosonization approaches. Studying deformations of this effective field theory produces exact results in the bosonic sector of nonFermi liquids. 
Thursday, March 17, 2022 3:12PM  3:24PM 
W64.00002: Constraints on compressible metals through emergent symmetries and anomalies Dominic Else, Senthil Todadri I will summarize recent work showing that the language of emergent symmetries and anomalies provides a powerful framework for thinking about properties of nonFermi liquids at low temperatures without reference to any particular model. I will argue that clean compressible metals necesssarily have a very nontrivial emergent symmetry and anomaly structure, likely associated with the existence of a Fermi surface. I will show how to understand Luttinger's theorem in a very general way using these ideas. 
Thursday, March 17, 2022 3:24PM  3:36PM 
W64.00003: Fermi liquids in the absence of charge quantization Joshuah T Heath LandauFermi liquid theory is a powerful tool to describe certain phases of stronglycorrelated fermionic matter. However, at a quantum critical point, the emergent collective fluctuations of the order parameter couple to the bare electrons, resulting in scaleinvariant behavior characterized by quantum critical exponents and the subsequent breakdown of a Fermi liquid picture. In the notorious "strange metal" nonFermi liquid phase of the cuprate superconductors, such quantum critical scaling predicts the breakdown of charge quantization and a modified form of Maxwell's equations. In this work, I will explore the fate of a Fermi liquid in close proximity to such a critical point by calculating the RPA and nonRPA contributions to the quasiparticle lifetime for generalized Coulomb and Amperean quasiparticle interactions when charge quantization is absent. The vector potential's anomalous dimension is found to have strong and highly nontrivial influence on the lifetime in both cases, however there exists regimes of stability where a traditional, Luttinger's theorempreserving Fermi liquid remains sensible. This work therefore opens new avenues to explore nearlycritical quantum matter with a Landau quasiparticle machinery. 
Thursday, March 17, 2022 3:36PM  3:48PM 
W64.00004: Frustration induced nonFermi liquid behavior. Juan F MendezValderrama, Debanjan Chowdhury Unconventional transport is often indicative of correlated electronic systems whose description lies beyond the Landau Fermi liquid paradigm. Understanding the mechanism by which nonFermi liquid behavior onsets in specific models remains a topic of great interest. I will discuss examples of intermediate scale nonFermi liquid and bad metallic transport in strongly interacting, frustrated models [1]. Building on this work, I will discuss the role that frustration can play in leading to deviations from Fermi liquid theory in general. 
Thursday, March 17, 2022 3:48PM  4:00PM 
W64.00005: Maximal quantum chaos of the critical Fermi surface Maria Tikhanovskaya, Subir Sachdev, Aavishkar A Patel We investigate the manybody quantum chaos of nonFermi liquid states in two spatial dimensions by computing their outoftimeorder correlation functions. Using a recently proposed largeN theory for the critical Fermi surface, and the ladder identity of Gu and Kitaev, we show that the chaos Lyapunov exponent takes the maximal value of 2 π T, where T is the absolute temperature. 
Thursday, March 17, 2022 4:00PM  4:12PM 
W64.00006: Metallic States with Charge Fractionalization Xiaochuan Wu, Mengxing Ye, ZhuXi Luo, Cenke Xu We construct examples of twodimensional metallic states with exotic behaviors at low and intermediate temperatures. The simplest example we construct involves fermionic partons of electrons at finite density coupled to a Z_N gauge field, whose properties can be studied through rudimentary methods. This simple state already has the following exotic features: (1) at low temperature this state is a "bad metal" whose resistivity can be much larger than the MottIoffeRegel limit; (2) while increasing temperature T the resistivity ρ(T) is a nonmonotonic function, and it crosses over from a bad metal at low T to a good metal at intermediate T; (3) the AC conductivity σ(ω) has a small Drude weight at low T, and a larger Drude weight at intermediate T; (4) at low temperature the metallic state has a large Lorenz number, which strongly violates the WiedemannFranz law; (5) the state also has a large thermopower (Seebeck coefficient). A more complex example with fermionic partons at finite density coupled to a SU(N) gauge field will also be discussed. Within a finite energy window, the physics is dominated by the nonfermi liquid fixed point of partons. The potential instability towards "color superconductivity" will also be discussed. In addition, we will illustrate how the SU(N) state reduces to the Z_N state using an N=3 example on the triangular lattice. 
Thursday, March 17, 2022 4:12PM  4:24PM 
W64.00007: Fingerprints of quantum criticality in locally resolved transport Xiaoyang Huang, Andrew Lucas Understanding electrical transport in strange metals, including the seeming universality of Planckian $T$linear resistivity, remains a longstanding challenge in condensed matter physics. We propose that local imaging techniques, such as nitrogenvacancy center magnetometry, can locally identify signatures of quantum critical response which are invisible in measurements of a bulk electrical resistivity. As an illustrative example, we use a minimal holographic model for a strange metal in two spatial dimensions to predict how electrical current will flow in regimes dominated by quantum critical dynamics on the Planckian length scale. We describe the crossover between quantum critical transport and hydrodynamic transport (including Ohmic regimes), both in chargeneutral and finite density systems. We compare our holographic predictions to experiments on chargeneutral graphene, finding quantitative agreement with available data; we suggest further experiments which may determine the relevance of our framework to transport on Planckian scales in this material. 
Thursday, March 17, 2022 4:24PM  4:36PM 
W64.00008: Electrical transport in a twodimensional disordered nonFermi liquid Tsz Chun Wu, Yunxiang Liao, Matthew Foster We study the electrical transport of a twodimensional nonFermi liquid with disorder, and we determine both the semiclassical dc conductivity and the first quantum correction. We consider a system with N flavors of fermions coupled to SU(N) critical matrix bosons. Motivated by the SYK model, we employ the bilocal field formalism and derive a set of saddle point equations governing the fermionic and bosonic selfenergies in the largeN limit. Interestingly, disorder smearing induces marginal Fermi liquid (MFL) behavior. Consequently, the resistivity varies linearly with temperature on top of the Drude result. We also consider fluctuations around the saddle points and derive a MFLFinkel’stein nonlinear sigma model. Using this theory, we evaluate the AltshulerAronov correction. In contrast with the Fermi liquid case, our calculation reveals a correction ~ ln^2(\Lambda/T) to the conductivity, which dominates in the lowtemperature regime. Our calculations explicitly satisfy the Ward identity at semiclassical and quantum levels. Our results can be tested directly in quantum critical systems via dc transport experiments. 
Thursday, March 17, 2022 4:36PM  4:48PM 
W64.00009: Bad metals in one dimension through fast Umklapp scattering Yanqi Wang, Roman Rausch, Christoph Karrasch, Joel E Moore A strongly interacting plasma of linearly dispersing electron and hole excitations in two spatial dimensions (2D), also known as a Dirac fluid, can be captured by relativistic hydrodynamics and shares many universal features with other quantum critical systems. We propose a onedimensional (1D) model to capture key aspects of the 2D Dirac fluid while being amenable to nonperturbative computation. When interactions add fast Umklapp scattering (FUS) to the Diraclike 1D dispersion, we show that this kind of irrelevant interaction is able to preserve Fermiliquidlike quasiparticle features while relaxing a zeromomentum charge current via collisions between particlehole excitations, leading to a Planckian dissipation (resistivity being linear in temperature). We further provide a microscopic lattice model, and numerically confirm the aforementioned features via densitymatrix renormalization (DMRG) simulation. 
Thursday, March 17, 2022 4:48PM  5:00PM 
W64.00010: A stability bound on the Tlinear resistivity of conventional metals Chaitanya Murthy, Esterlis Ilya, Akshat Pandey, Steven A Kivelson The electrical resistivity of conventional metals varies linearly with temperature T in the regime T > ω_{0}, where ω_{0} is a characteristic phonon frequency. The corresponding transport scattering rate is 1/τ_{tr }= 2π λT, where λ is a dimensionless strength of the electronphonon coupling. The fact that measured values satisfy λ < ~1 has been noted in the context of a possible "Planckian" bound on transport. However, since the electronphonon scattering is quasielastic in this regime, it is unlikely that Planckian considerations are relevant. We present results on the Holstein model which show that a different sort of bound is at play: a "stability" bound on λ consistent with metallic transport. We conjecture that a qualitatively similar bound on the strength of residual interactions may apply to metals more generally. 
Thursday, March 17, 2022 5:00PM  5:12PM 
W64.00011: Effects of quenched nonmagnetic disorder on a spindensitywave quantum critical metallic system Iksu Jang, KiSeok Kim We investigate effects of general quenched nonmagnetic disorder on a spindensitywave(SDW) quantum critical metallic system using a renormalization group method. As effects of quenched nonmagnetic disorder, (i) random charge potential and (ii) random mass of a SDW boson order parameter are considered. Two regularization methods; codimensional regularization and a correlated random mass method are used in our renormalization group analysis. In oneloop result, there is no stable fixed and low energy RGflows are governed by the large random charge potential vertices and an effective Yukawa interaction. Beyond the oneloop results, possiblity of the another strongly disordered phase due to the random boson mass vertex is discussed. Regarding to the physical properties, low energy behavours of the two point Green's functions and anomalous dimensions of several superconducting channels are discussed. It is found zero momentum dwave superconducting channel is suppressed due to the effects of the disorder. We hope that our research give guidance and intuition about effects of quenched nonmagnetic disorder on nonFermi liquid states. 
Thursday, March 17, 2022 5:12PM  5:24PM 
W64.00012: Transport in the emergent Bose liquid: bad metal, strange metal, and weak insulator, all in one system Tao Zeng Nonsaturating hightemperature resistivity (“bad metal”), Tlinear lowtemperature resistivity (“strange metal”), and a crossover to activationfree growth of the resistivity in the lowtemperature limit (“weak insulator”) are among the most exotic behaviors widely observed in many strongly correlated materials that defy the standard Fermi liquid description of solids. Here we investigate these puzzling behaviors by computing temperaturedependent optical conductivity of an emergent Bose liquid and find that it reproduces all the unexplained features of the experiments, including a featureless continuum and a wellknown midinfrared peak. Amazingly and with physically intuitive mechanisms, the corresponding doping and temperaturedependent resistivity displays the bad metal and strange metal simultaneously and sometimes weak insulating behaviors as well. The unification of all these nonFermi liquid behaviors under a single model strongly supports a new paradigm: The lowenergy physics in a large class of strongly correlated materials may be dominated by a new quantum state of matter, namely the emergent Bose liquid. 
Thursday, March 17, 2022 5:24PM  5:36PM 
W64.00013: Probing a Bose Metal via Electrons: Inescapable nonFermi liquid scattering and pseudogap physics Wei Ku, Xinlei Yue, Anthony C Hegg, Xiang Li NonFermi liquid behavior and pseudogap formation are among the most wellknown examples of exotic spectral features observed in several strongly correlated materials such as the holedoped cuprates, nickelates, iridates, ruthenates, ferropnictides, doped Mott organics, transition metal dichalcogenides, heavy fermions, $d$ and $f$electron metals, etc. We demonstrate that these features are inevitable consequences when fermions couple to an unconventional Bose metal mean field consisting of lowerdimensional coherence. Not only do we find both exotic phenomena, but also a host of other features that have been observed e.g. in the cuprates including nodal antinodal dichotomy and pseudogap asymmetry(symmetry) in momentum(real) space. Obtaining these exotic and heretofore mysterious phenomena via a mean field offers a simple, universal, and therefore widely applicable explanation for their ubiquitous empirical appearance. 
Thursday, March 17, 2022 5:36PM  5:48PM 
W64.00014: Lifshitz electrodynamics with Luttinger fermions Santanu Dey, Joseph Maciejko Threedimensional Luttinger fermions have quadratic band touching dispersion with Lifshitzlike dynamical scaling z = 2. We extend the singleparticle Luttinger Hamiltonian to include the effects of minimally coupled gauge fluctuations and illustrate the longwavelength behavior of the combined interacting system. Within the parameter space of our model, we discover an analog of the nonFermi liquid phase found in Luttinger semimetals with static Coulomb interaction. We further show that dynamical gauge fluctuations can also lead to nonrelativistic Lifshitz scaling for the emergent photons in our theory. With an RG analysis, we describe the stability and scaling properties of its fixed points in the presence of additional cubicsymmetry allowed perturbations. 
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