C. A. Lamas, D. C. Cabra, N. Grandi
We develop a procedure for detecting Fermi liquid instabilities by extending the analysis of Pomeranchuk to two-dimensional lattice systems. The method is very general and straightforward to apply, thus providing a powerful tool for the search of exotic phases. We test it by applying it to a lattice electron model with interactions leading to $s$ and d-wave instabilities.
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Hidden duality and associated instabilities of the spinless Luttinger liquid on lattice are reported. The local quantum fluctuations and the long-distance chiral modes compete and as a result produce a hierarchy of exotic charge/density instabilities. Explicit bosonic quantum operators for the local density fluctuations are constructed and are used to make identification of the Luttinger liquid with the classical 2D Coulomb gas with $θ$-term and with the rich hidden duality.
We discuss the appearance of magnetic and charge instabilities, named respectively metamagnetism (MM) and phase separation (PS), in systems which can be described by a perturbed Luttinger liquid. We argue that such instabilities can be associated with the vanishing of the effective Fermi velocity v, which in some cases coincides with a divergence of the effective Luttinger parameter K. We analyze in particular an XXZ chain with next-nearest-neighbor interactions in different limits where MM shows up and an extended Hubbard model where in turn, PS occurs. Qualitative agreement with previous stu…
We study systems made of periodic arrays of one dimensional quantum wires, coupled by Coulomb interaction. Using bosonization an interacting metallic fixed point is obtained, which is shown to be a higher dimensional analogue of the Tomonaga-Luttinger liquid, or a sliding Luttinger liquid. This non-Fermi liquid metallic state, however, is unstable in the presence of weak interwire backscatterings, which favor charge density wave states and suppress pairing. Depending on the effective strength of the Coulomb repulsion and the size of interwire spacing various charge density wave states are stab…
The emergent behavior of spin liquids that are born out of geometrical frustration makes them an intriguing state of matter. We show that in the quantum kagome antiferromagnet ZnCu$_3$(OH)$_6$SO$_4$ several different correlated, yet fluctuating states exist. By combining complementary local-probe techniques with neutron scattering, we discover a crossover from a critical regime into a gapless spin-liquid phase with decreasing temperature. An additional unconventional instability of the latter phase leads to a second, distinct spin-liquid state that is stabilized at the lowest temperatures. We …
We study the effects of spin-antisymmetric interactions on the stability of a Landau-Fermi liquid on the square lattice, using the generalized Pomeranchuk method for two-dimensional lattice systems. In particular, we analyze interactions that could induce instabilities of the so called spin-split type, that is when spin-up and spin-down Fermi surfaces are displaced with respect to each other. The phase space is studied as a function of the strength of the interaction $V$, the electron chemical potential $μ$ and an external magnetic field $h$. We find that such interactions produce in general a…
This paper is a short review on the foundations and recent advances in the microscopic Fermi-liquid (FL) theory. We demonstrate that this theory is built on five identities, which follow from conservation of total charge (particle number), spin, and momentum in a translationally and $SU(2)$-invariant FL. These identities allows one to express the effective mass and quasiparticle residue in terms of an exact vertex function and also impose constraints on the "quasiparticle" and "incoherent" (or "low-energ" and "high-energy") contributions to the observable quantities. Such constraints forbid ce…
Three-dimensional (3D) variants of the Kitaev model can harbor gapless spin liquids with a Majorana Fermi surface on certain tricoordinated lattice structures such as the recently introduced hyperoctagon lattice. Here we investigate Fermi surface instabilities arising from additional spin exchange terms (such as a Heisenberg coupling) which introduce interactions between the emergent Majorana fermion degrees of freedom. We show that independent of the sign and structure of the interactions, the Majorana surface is always unstable. Generically the system spontaneously doubles its unit cell at e…
We study the instabilities caused by four fermion interactions on algebraic spin liquids. Renormalization group (RG) is used for three types of previously proposed spin liquids on the square lattice: the staggered flux state of SU(2) spin system, the $π-$flux state of SU(4) spin system, and the $π-$flux state of SU(2) spin system. The low energy field theories of the first two types of spin liquids are QED3 with emerged SU(4) and SU(8) flavor symmetries, the low energy theory of the $π-$flux SU(2) spin liquid is the QCD3 with SU(2) gauge field and emergent Sp(4) (SO(5)) flavor symmetry. Suitab…
We investigate the competing Fermi surface instabilities in the Kagome tight-binding model. Specifically, we consider onsite and short-range Hubbard interactions in the vicinity of van Hove filling of the dispersive Kagome bands where the Fermiology promotes the joint effect of enlarged density of states and nesting. The sublattice interference mechanism [Kiesel and Thomale, Phys. Rev. B Rapid Comm., in press.] allows us to explain the intricate interplay between ferromagnetic fluctuations and other ordering tendencies. On the basis of functional renormalization group used to obtain an adequat…
We respond to the comment arXiv:1809.03931 put forward by Li-Han Chen, Zhen Liu, and Jian-Tin Zheng on our work Kiesel, Platt, and Thomale, Phys. Rev. Lett. 110, 126405 (2013). All misunderstandings and misconceptions communicated in the comment are addressed in light of the status quo of functional renormalization group.
We study the presence of Pomeranchuk instabilities induced by interactions on a Fermi liquid description of a graphene layer. Using a recently developed generalization of Pomeranchuk method we present a phase diagram in the space of fillings versus on-site and nearest neighbors interactions. Interestingly, we find that for both interactions being repulsive an instability region exists near the Van Hove filling, in agreement with earlier theoretical work. In contrast, near half filling, the Fermi liquid behavior appears to be stable, in agreement with theoretical results and experimental findin…
We present a theory of spontaneous Fermi surface deformations for half-filled Landau levels (filling factors of the form $ν=2n+1/2$). We assume the half-filled level to be in a compressible, Fermi liquid state with a circular Fermi surface. The Landau level projection is incorporated via a modified effective electron-electron interaction and the resulting band structure is described within the Hartree-Fock approximation. We regulate the infrared divergences in the theory and probe the intrinsic tendency of the Fermi surface to deform through Pomeranchuk instabilities. We find that the correspo…
Hund's coupling is shown to generally favor, in a doped half-filled Mott insulator, an increase in the compressibility culminating in a Fermi-liquid instability towards phase separation. The largest effect is found about the frontier between an ordinary and an orbitally-decoupled ("Hund's") metal. The increased compressibility implies an enhancement of quasiparticle scattering, thus favoring other possible symmetry breakings. This physics is shown to happen in simulations of the 122 Fe-based superconductors, possibly implying the relevance of this mechanism in the enhancement of the the critic…
This review discusses instabilities of the Fermi-liquid state of conduction electrons in metals with particular emphasis on magnetic quantum critical points. Both the existing theoretical concepts and experimental data on selected materials are presented; with the aim of assessing the validity of presently available theory. After briefly recalling the fundamentals of Fermi-liquid theory, the local Fermi-liquid state in quantum impurity models and their lattice versions is described. Next, the scaling concepts applicable to quantum phase transitions are presented. The Hertz-Millis-Moriya theory…
We elucidate the close relationship between spontaneous time-reversal symmetry breaking and the physics of excitonic instabilities in strongly correlated multiband systems. The underlying mechanism responsible for the spontaneous breaking of time-reversal symmetry in a many-body system is closely related to the Cooper-like pairing instability of interband particle-hole pairs involving higher order symmetries. Studies of such pairing instabilites have, however, mainly focused on the mean-field aspects of the virtual exciton condensate, which ignores the presence of the underlying collective Fer…
Quantum spin liquids (QSLs) are exotic phases of matter exhibiting long-range entanglement and supporting emergent gauge fields. A vigorous search for experimental realizations of these states has identified several materials with properties hinting at QSL physics. A key issue in understanding these QSL candidates is often the interplay of weak disorder of the crystal structure with the spin liquid state. It has recently been pointed out that in at least one important class of candidate QSLs - pyrochlore magnets based on non-Kramers ions such as Pr$^{3+}$ or Tb$^{3+}$- structural disorder can …
Fermi liquids beyond the forward scattering limit: the role of non-forward scatterings for scale invariance and instabilities
本研究利用场论泛函重整化群修正费米液体理论，证明含小动量转移非前向散射的局域标度不变不动点存在，揭示非前向散射驱动的粒子-空穴、粒子-粒子通道不稳定性及相关普适低能动力学。
The paramagnetic phase of the extended attractive Hubbard model on the cubic lattice is studied within the spin rotation invariant Kotliar-Ruckenstein slave-boson representation at zero temperature. It is obtained that the quasiparticle residue of the Fermi liquid phase vanishes for all densities at an interaction strength slightly smaller than $U_c$ that signals the Brinkman-Rice transition, and that it weakly depends on density. While for vanishing non-local interaction parameters homogeneous static charge instabilities are found in a rather narrow window centered around quarter filling and …
We study the spin-one Kitaev model on the honeycomb lattice in the presence of single-ion anisotropies. We consider two types of single ion anisotropies: A $D_{111}$ anisotropy which preserves the symmetry between $X$, $Y$, and $Z$ bonds but violates flux conservation and a $D_{100}$ anisotropy that breaks the symmetry between $X$, $Y$, and $Z$ bonds but preserves flux conservation. We use series expansion methods, degenerate perturbation theory, and exact diagonalization to study these systems. Large positive $D_{111}$ anisotropy leads to a simple product ground state with conventional magnon…
We study in this paper the general properties of a many body system of fermions in arbitrary dimensions assuming that the {\em momentum} of individual fermions are good quantum numbers of the system. We call these systems $k$-Fermi liquids. We show how Fermi liquid, Luttinger liquid (or Fermi liquid with exclusion statistics) and spin-charge separation arises from this framework. Two exactly solvable $k$-Fermi liquid models with spin-charge separation are discussed as examples.
It is well-known that, generically, the one-dimensional interacting fermions cannot be described in terms of the Fermi liquid. Instead, they present different phenomenology, that of the Tomonaga-Luttinger liquid: the Landau quasiparticles are ill-defined, and the fermion occupation number is continuous at the Fermi energy. We demonstrate that suitable fine-tuning of the interaction between fermions can stabilize a peculiar state of one-dimensional matter, which is dissimilar to both the Tomonaga-Luttinger and Fermi liquids. We propose to call this state a quasi-Fermi liquid. Technically speaki…
Single monkey-saddle singularity of a Fermi surface and its instabilities
本文研究费米面高阶猴鞍奇点在不破坏时间反演和反演对称性时成对出现，并探讨孤立奇点在不同相互作用下的稳定性，发现自旋电子中排斥作用破坏奇点，而无自旋电子在平均场下可稳定。
Chiral Instabilities in Driven-Dissipative Quantum Liquids
本文使用Floquet-Lindblad方法研究周期性驱动TLLs的非平衡动力学，发现纯手性热浴耦合能引发驱动-耗散相变，导致单一手性准粒子指数放大并产生动态手性失衡。
The interplay of non-Fermi liquid and superconductivity born out of strong dynamical interactions is at the heart of the physics of unconventional superconductivity. As a solvable platform of the strongly correlated superconductors, we study the pairing instabilities of the Yukawa-Sachdev-Ye-Kitaev (Yukawa-SYK) model, which describes spin-1/2 fermions coupled to bosons by the random, all-to-all, spin-independent and dependent Yukawa interactions. In contrast to the previously studied models, the random Yukawa couplings are sampled from a collection of Gaussian ensembles whose variances follow …
Electron-Phonon Functional Renormalization Group of Fermi Liquid Instabilities
该研究为关联电子模型制定泛函重整化群假设，纳入电子相互作用与电子-声子耦合，平等对待声子和电子介导的费米液体不稳定性，以哈伯德模型为例说明方法，可纳入完整输入，有助于分析微观层面电子序。
We propose in this paper an effective low-energy theory for interacting fermion systems which supports exclusion statistics. The theory can be viewed as an extension of Landau Fermi liquid theory where besides quasi-particle energy $ξ_{\mathbf{k}}$, the kinetic momentum $\mathbf{k}$ of quasi-particles depends also on quasi-particle occupation numbers as a result of momentum ($k$)-dependent current-current interaction. The dependence of kinetic momentum on quasi-particles excitations leads to change in density of states and exclusion statistics. The properties of this new Fermi liquid state is …
We develop a theory for a generic instability of a Fermi liquid in dimension d>1 against the formation of a Luttinger-liquid-like state. The density of states at the Fermi level is the order parameter for the ensuing quantum phase transition, which is driven by the effective interaction strength. A scaling theory in conjunction with an effective field theoy for clean electrons is used to obtain the critical behavior of observables. In the Fermi-liquid phase the order-parameter susceptibility, which is measurable by tunneling, is predicted to diverge for 1<d<3.
Microscopic Mechanism of Pair-, Charge- and Spin-Density-Wave Instabilities in Interacting D-Dimensional Fermi Liquids
本文通过单圈重整化群和玻色化方法，揭示相互作用D维费米液体中自旋/电荷密度波、激子绝缘体、非BCS超导及配对密度波不稳定性的微观机制，为多种量子材料的量子相变提供统一理论基础。
Recent experiments in the underdoped regime of the hole-doped cuprates have found evidence for an incommensurate charge density wave state. We present an analysis of the charge ordering instabilities in a metal with antiferromagnetic correlations, where the electronic excitations are coupled to the fractionalized excitations of a quantum fluctuating antiferromagnet on the square lattice. The resulting charge density wave state emerging out of such a fractionalized Fermi-liquid (FL*) has wavevectors of the form $(\pm Q_0,0), (0,\pm Q_0)$, with a predominantly $d$-form factor, in agreement with …
We extend and apply a recent theory of the dynamical spin response of Anderson lattice systems to interpret ESR data on YbRh2Si2. Starting within a semiphenomenological Fermi liquid description at low temperatures T < Tx (a crossover temperature) and low magnetic fields B << Bx, we extend the description to the non-Fermi liquid regime by adopting a quasiparticle picture with effective mass and spin susceptibility varying logarithmically with energy/temperature, as observed in experiment. We find a sharp ESR resonance line slightly shifted from the local f-level resonance and broadened by quasi…
We derive a general set of Poor Man's scaling equations and analyze the stability of the Luttinger state in a system composed of a finite number N of one dimensional spinless fermionic chains, coupled through a general two body interaction. The effect of processes with momentum transfer parallel to the Fermi surface in destroying massless states is investigated. It will be shown that there are two processes competing: one in which two electrons exchange chains and the other in which they jump into a same chain. When periodic boundary conditions in the transverse direction are taken into accoun…
We show that thermodynamics is insufficient to probe the nature of the low energy dynamics of quantum impurity models and a more subtle analysis based on scattering theory is required. Traditionally, quantum impurity models are classified into one of two categories: Fermi liquids and non-Fermi liquids, depending on the analytic properties of the various thermodynamic quntities. We show, however, that even when a quantum impurity model is a Fermi liquid (an incoming electron at the Fermi level scatters elastically off the impurity), one may find singular thermodynamic behavior if characteristic…
We show that the one-dimensional (1D) electron systems can also be described by Landau's phenomenological Fermi-liquid theory. Most of the known results derived from the Luttinger-liquid theory can be retrieved from the 1D Fermi-liquid theory. Exact correspondence between the Landau parameters and Haldane parameters is established. The exponents of the dynamical correlation functions and the impurity problem are also discussed based on the finite size corrections of elementary excitations with the predictions of the conformal field theory, which provides a bridge between the 1D Fermi-liquid an…
We study the longitudinal sound propagation in the electronic nematic Fermi liquid where the Fermi surface is distorted due to the spontaneously broken rotational symmetry. The behavior of the sound wave in the nematic ordered state is dramatically different from that in the isotropic Fermi liquid. The collective modes associated with the fluctuations of the Fermi surface distortion in the nematic Fermi liquid leads to the strong and anisotropic damping of the sound wave. The relevance of the nematic Fermi liquid in doped Mott insulator is discussed.
In these lecture notes, the basic physics of Fermi liquids and Luttinger liquids is presented. Fermi liquids are discussed both from a phenomenological viewpoint, in relation to microscopic approaches, and as renormalization group fixed points. Luttinger liquids are introduced using the bosonization formalism, and their essential differences with Fermi liquids are pointed out. Applications to transport effects, the effect of disorder, quantum spin chains, and spin ladders, both insulating and metallic, are given.
We show that a strongly correlated Fermi system with the fermion condensate, which exhibits strong deviations from Landau Fermi liquid behavior, is driven into the Landau Fermi liquid by applying a small magnetic field $B$ at temperature T=0. This field-induced Landau Fermi liquid behavior provides the constancy of the Kadowaki-Woods ratio. A reentrance into the strongly correlated regime is observed if the magnetic field $B$ decreases to zero, then the effective mass $M^*$ diverges as $M^*\propto 1/\sqrt{B}$. At finite temperatures, the strongly correlated regime is restored at some temperatu…
An intense investigation of possible non-Fermi liquid states of matter has been inspired by two of the most intriguing phenomena discovered in the past quarter century, namely high temperature superconductivity and the fractional quantum Hall effect. Despite enormous conceptual strides, these two fields have developed largely along separate paths. Two widely employed theories are the resonating valence bond theory for high temperature superconductivity and the composite fermion theory for the fractional quantum Hall effect. The goal of this "perspective" article is to note that they subscribe …
Non-Fermi liquid behavior of strongly correlated Fermi systems is derived within the Landau approach. We attribute this behavior to a phase transition associated with a rearrangement of the Landau state that leads to flattening of a portion of the single-particle spectrum $ε({\bf p})$ in the vicinity of the Fermi surface. We demonstrate that the quasiparticle subsystem responsible for the flat spectrum possesses the same thermodynamic properties as a gas of localized spins. Theoretical results compare favorably with available experimental data. While departing radically from prevalent views on…
A crossover from a non-Fermi liquid to a Fermi liquid phase in Yb$_2$Ni$_{12}$P$_7$ is observed by analyzing electrical resistivity $ρ(T)$, magnetic susceptibility $χ(T)$, specific heat $C(T)$, and thermoelectric power $S(T)$ measurements. The electronic contribution to specific heat, $C_{e}(T)$, behaves as $C_{e}(T)/T \sim -\ln(T)$ for 5 K $< T <$ 15 K, which is consistent with non-Fermi liquid behavior. Below $T \sim$ 4 K, the upturn in $C_{e}(T)/T$ begins to saturate, suggesting that the system crosses over into a Fermi-liquid ground state. This is consistent with robust $ρ(T) - ρ_0 = AT^2$…
This paper is concerned with the weak-moment magnetism in heavy-fermion materials and its relation to the non-Fermi liquid physics observed near the transition to the Fermi liquid. We explore the hypothesis that the primary fluctuations responsible for the non-Fermi liquid physics are those associated with the destruction of the large Fermi surface of the Fermi liquid. Magnetism is suggested to be a low-energy instability of the resulting small Fermi surface state. A concrete realization of this picture is provided by a fractionalized Fermi liquid state which has a small Fermi surface of condu…
We study the effect of electron hopping in triple quantum dots modelled by the three-impurity Anderson model. We determine the range of hopping parameters where the system exhibits the two-channel Kondo effect and has non-Fermi-liquid properties in a wide temperature interval. As this interval is entered from above, the conductance through the side dots increases to a half of the conductance quantum, while the conductance through the system remains small. At lower temperatures the conductance through the system increases to the unitary limit as the system crosses over to the Fermi-liquid groun…
We present different transport measurements up to fields of 29~T in the recently discovered heavy-fermion superconductor UTe$_{2}$ with magnetic field $H$ applied along the easy magnetization a-axis of the body-centered orthorhombic structure. The thermoelectric power varies linearly with temperature above the superconducting transition, $T_{SC}= 1.5$ K, indicating that superconductivity develops in a Fermi liquid regime. As a function of field the thermolelectric power shows successive anomalies which are attributed to field-induced Fermi surface instabilities. These Fermi-surface instabiliti…
I demonstrate a contradiction which arises if we assume that the Fermi surface in a heavy electron metal represents a finite jump in occupancy.
We study the Fermi surface instabilities of the Pomeranchuk type in the spin triplet channel with high orbital partial waves ($F_{l}^a ~(l>0)$). The ordered phases are classified into two classes, dubbed the $α$ and $β$-phases by analogy to the superfluid $^3$He-A and B-phases. The Fermi surfaces in the $α$-phases exhibit spontaneous anisotropic distortions, while those in the $β$-phases remain circular or spherical with topologically non-trivial spin configurations in momentum space. In the $α$-phase, the Goldstone modes in the density channel exhibit anisotropic overdamping. The Goldstone mo…
We study the density instabilities of a two-dimensional gas of dipolar fermions with aligned dipole moments. We show that the Random Phase Approximation (RPA) for the density-density response function is never accurate for the dipolar gas. We incorporate correlations beyond RPA via an improved version of the Singwi-Tosi-Land-Sjolander scheme. In addition to density-wave instabilities, our formalism captures the collapse instability that is expected from Hartree-Fock calculations but is absent from RPA. Crucially, we find that when the dipoles are perpendicular to the layer, the system spontane…
Effects of perturbations on topologically ordered (TO) states with fractionalized excitations is very intriguing. While small perturbations are not expected to affect a robust TO, sizable perturbations must lead to onset of novel routes to order(s). Observability of such emergent orders in real condensed matter systems continues to be an open issue of paramount interest. Here, we detail how a featureless Kitaev spin liquid with rigorous TO gives way to partial topological ordered state(s) coexisting with a wide staircase of novel `excitonic' orders of fractionalized entities in a Zeeman field.…
Non-Fermi liquid behaviour of CDW instabilities in fractionally-filled moiré flatbands
研究通过构建最小有效作用，揭示了二维莫尔平带中分数填充分子序的非费米液体行为，源于库仑相互作用导致的电荷密度波有序。
We present a new method to detect Fermi surface instabilities for interacting systems at finite temperature. We first apply it to a list of cases studied previously, recovering already known results in a very economic way, and obtaining most of the information on the phase diagram analytically. As an example, in the continuum limit we obtain the critical temperature as an implicit function of the magnetic field and the chemical potential $T_c(μ,h)$. By applying the method to a model proposed to describe reentrant behavior in $Sr_3Ru_2O_7$, we reproduce the phase diagram obtained experimentally…
This is a comment on Phys. Rev. Lett. {\bf 110}, 126405 (2013), showing it biases the ferromagnetic order more than mean field theories would do. With over-biases like this, the theoretical method applied in the given context is called into question.
We address at the mean field level the emergence of a Pomeranchuk instability in a uniform Fermi liquid with \emph{central} particle-particle interactions. We find that Pomeranchuk instabilities with all symmetries except $l=1$ can take place if the interaction is repulsive and has a finite range $r_{0}$ of the order of the inter-particle distance. We demonstrate this by solving the mean field equations analytically for an explicit model interaction, as well as numerical results for more realistic potentials. We find in addition to the Pomeranchuk instability other, subtler phase transitions i…
We study the competition between the nematic and the hexatic phases of a two-dimensional spinless Fermi fluid near Pomeranchuk instabilities. We show that the general phase diagram of this theory contains a bicritical point where two second order lines and a first order nematic/hexatic phase transition meet together. We found that at criticality, and deep inside the associated symmetry broken phases, the low energy theory is governed by a dissipative cubic mode, even near the bicritical point where nematic and hexatic fluctuations cannot be distinguished due to very strong dynamical couplings.
Renormalization Group Analysis of Pairing Instabilities in Nuclear Fermi Liquids
该研究通过费米面重整化群分析，在最简S/P波模型中阐明核费米液体不同通道配对不稳定性的竞争机制，发现费米面几何、组分及同位旋不对称性会改变配对不稳定性的排序。
The zero-temperature phase diagram of $p$-orbital two-component fermionic system loaded into a one-dimensional optical lattice is mapped out by means of analytical and numerical techniques. It is shown that the $p$-band model away from half-filling hosts various competing superconducting phases for attractive and repulsive interactions. At quarter filling, we analyze the possible formation of incompressible Mott phases and in particular for repulsive interactions, we find the occurrence of a Mott transition with the formation of fully gapped bond-ordering waves.
Diffusion and instabilities in large-N holographic Fermi liquids: the vector fluctuations of the electron star
本文研究AdS电子星矢量扇区的流体动力学响应，发现低温及临界温度附近存在流体动力学行为，中间温度则不存在，并揭示有限温度下正虚频率轴上的不稳定性极点，暗示理想流体极限可能是假真空。
We study the quantum critical phenomena emerging at the transition from triple-Weyl semimetal to band insulator, which is a topological phase transition described by the change of topological invariant. The critical point realizes a new type of semimetal state in which the fermion dispersion is cubic along two directions and quadratic along the third. Our renormalization group analysis reveals that, the Coulomb interaction is marginal at low energies and even arbitrarily weak Coulomb interaction suffices to induce an infrared fixed point. We compute a number of observable quantities, and show …
Experiments on quantum degenerate Fermi gases of magnetic atoms and dipolar molecules begin to probe their broken symmetry phases dominated by the long-range, anisotropic dipole-dipole interaction. Several candidate phases including the p-wave superfluid, the stripe density wave, and a supersolid have been proposed theoretically for two-dimensional spinless dipolar Fermi gases. Yet the phase boundaries predicted by different approximations vary greatly, and a definitive phase diagram is still lacking. Here we present a theory that treats all competing many-body instabilities in the particle-pa…
We construct a family of translationally invariant lattice models with a large number ($N$) of orbitals at every site coupled together via single electron tunneling. By tuning the relative strength of the electronic bandwidth and on-site interactions, that have a modified Sachdev-Ye-Kitaev (SYK) form, we demonstrate a number of unusual features at strong coupling and in the large$-N$ limit. We find examples of (i) an intrinsic non-BCS superconducting instability arising out of an incoherent non-Fermi liquid metal, and, (ii) an instability of an incipient heavy Fermi liquid metal to superconduc…
Two-dimensional quantum antiferromagnets host rich physics, including long-range ordering, high-$T_c$ superconductivity, quantum spin liquid behavior, topological ordering, a variety of other exotic phases, and quantum criticalities. Frustrating perturbations in antiferromagnets may give rise to strong quantum fluctuations, challenging the theoretical understanding of the many-body ground state. Here we develop a method to describe the quantum antiferromagnets using fermionic degrees of freedom. The method is based on a formally exact mapping between spin exchange models and theories describin…
Van-Hove tuning of Fermi surface instabilities through compensated metallicity
通过补偿金属性在石墨烯电子蜂窝晶格模型中解锁vH驱动的配对，实现接近半填充的高温拓扑超导性。
Robust Fermi liquid instabilities in sign problem-free models
本文证明DQMC已知无符号类模型在d≥2中通常无法拥有稳定费米液体基态，揭示费米液体与费米子符号问题的根本联系。
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