Related papers: Collective modes near a Pomeranchuk instability
It is generally believed that the BCS-BEC evolution in fermionic systems with s-wave pairing is a smooth crossover. However, for nonzero orbital-angular-momentum pairing such as p- or d-wave pairing, the system undergoes a quantum phase…
The quantum ferromagnetic transition of itinerant electrons is considered. We give a pedagogical review of recent results which show that zero-temperature soft modes that are commonly neglected, invalidate the standard…
We describe two dimensional models with a metallic Fermi surface which display quantum phase transitions controlled by strongly interacting critical field theories below their upper critical dimension. The primary examples involve…
We show that a two-dimensional (2D) isotropic Fermi liquid harbors two new types of collective modes, driven by quantum fluctuations, in addition to conventional zero sound: "hidden" and "mirage" modes. The hidden modes occur for relatively…
In this paper, collective excitations in a homogeneous fermion-fermion mixture with different Fermi surfaces are studied. In the Fermi liquid phase, the zero-sound velocity is found to be larger than the largest Fermi velocity. With…
Synchronization transition in oscillatory networks manifests itself as the appearance of a periodic global mode. While perfect in the thermodynamic limit, this mode fluctuates for finite ensembles. We characterize the coherence of this mode…
In two-dimensional systems with a continuous symmetry the Mermin-Wagner-Hohenberg theorem precludes spontaneous symmetry breaking and condensation at finite temperature. The Berezinskii-Kosterlitz-Thouless critical temperature marks the…
Experiments in heavy-fermion metals and related theoretical work suggest that critical local-moment fluctuations can play an important role near a zero-temperature phase transition. We study such fluctuations at the quantum critical point…
We study the Kondo-Heisenberg model using a fermionic representation for the localized spins. The mean-field phase diagram exhibits a zero temperature quantum critical point separating a spin liquid phase where the f-conduction…
The $j = 3/2$ fermions in cubic crystals or cold atomic gases can form Cooper pairs in both singlet ($J = 0$) and unconventional quintet ($J = 2$) $s$-wave states. Our study utilizes analytical field theory to examine fluctuations in these…
A nonlocal string order parameter detecting topological order and deconfinement has been proposed by Fredenhagen and Marcu (FM). However, due to the lack of exact internal symmetries for lattice models and the nonlinear dependence of the FM…
$YbInCu_{4}$ and its alloys present discontinuous, first order iso-structural transitions at pressure dependent temperatures $T_V(P)$, where a local moment phase coexist with a renormalized Fermi liquid phase. We show that along the…
We study a model for a quantum critical point in two spatial dimensions between a semimetallic phase, characterized by a stable quadratic Fermi node, and an ordered phase, in which the spectrum develops a band gap. The quantum critical…
A fully analytical theory of a traveling soliton in a one-dimensional fermionic superfluid is developed within the framework of time-dependent self-consistent Bogoliubov-de Gennes equations, which are solved exactly in the Andreev…
We investigate traveling solitons of a one-dimensional spin-orbit coupled Fermi superfluid in both topologically trivial and non-trivial regimes by solving the static and time-dependent Bogoliubov-de Gennes equations. We find a critical…
We use electronic Raman scattering to study the low-energy excitations in BaFe$_2$(As$_{0.5}$P$_{0.5}$)$_2$ ($T_c \approx 16$ K) samples. In addition to a superconducting pair breaking peak (2$\Delta=6.7$ meV) in the A$_{1g}$ channel with a…
We show that a large class of two-dimensional spinless fermion models exhibit topological superconducting phases characterized by a non-zero Chern number. More specifically, we consider a generic one-band Hamiltonian of spinless fermions…
The Lyapunov spectrum describes the exponential growth, or decay, of infinitesimal phase-space perturbations. The perturbation associated with the maximum Lyapunov exponent is strongly localized in space, and only a small fraction of all…
We develop a method to detect instabilities leading to nematic phases in strongly coupled metallic systems. We do so by adapting the well-known Pomeranchuk technique to a weakly coupled system of fermions in a curved asymptotically AdS…
Goldstone modes emerge associated with spontaneous breakdown of the continuous symmetry in the two-channel Kondo lattice, which describes strongly correlated f-electron systems with a non-Kramers doublet at each site. This paper derives the…