Yoni Schattner

Ising nematic quantum critical point in a metal: a Monte Carlo study

The Ising nematic quantum critical point (QCP) associated with the zero temperature transition from a symmetric to a nematic {\it metal} is an exemplar of metallic quantum criticality. We have carried out a minus sign-free quantum Monte Carlo study of this QCP for a two dimensional lattice model with sizes up to

Superconductivity and non-Fermi liquid behavior near a nematic quantum critical point

24\times 24

Non-Fermi Liquid at ( 2+1 ) D Ferromagnetic Quantum Critical Point

sites. The system remains non-superconducting down to the lowest accessible temperatures. The results exhibit critical scaling behavior over the accessible ranges of temperature, (imaginary) time, and distance. This scaling behavior has remarkable similarities with recently measured properties of the Fe-based superconductors proximate to their putative nematic QCP.

Superconductivity mediated by quantum critical antiferromagnetic fluctuations: The rise and fall of hot spots

Significance It has been conjectured that many properties of highly correlated materials, including high-temperature superconductivity, may arise from proximity to a metallic quantum critical point. However, the nature of quantum critical phenomena in metals is incompletely understood. Using numerically exact quantum Monte Carlo methods, we simulated a model that can be tuned through a metallic quantum critical point and observed behaviors that are strikingly reminiscent of experiments. Among these phenomena are high-temperature superconductivity, non-Fermi liquid behavior of the electron Green function, and “bad metal” behavior of the electrical conductivity. Using determinantal quantum Monte Carlo, we compute the properties of a lattice model with spin 12 itinerant electrons tuned through a quantum phase transition to an Ising nematic phase. The nematic fluctuations induce superconductivity with a broad dome in the superconducting Tc enclosing the nematic quantum critical point. For temperatures above Tc, we see strikingly non-Fermi liquid behavior, including a “nodal–antinodal dichotomy” reminiscent of that seen in several transition metal oxides. In addition, the critical fluctuations have a strong effect on the low-frequency optical conductivity, resulting in behavior consistent with “bad metal” phenomenology.

Transverse thermoelectric response as a probe for existence of quasiparticles

The behavior of electrons near quantum critical points, such as magnetic phase transitions at temperatures approaching absolute zero, are of vital interest but are extremely challenging to understand. New computer simulations solve this problem, exactly, for one example of these strange metals and reveal a new type of quantum critical point.

Competing Orders in a Nearly Antiferromagnetic Metal

In several unconventional superconductors, the highest superconducting transition temperature

Spin density wave order, topological order, and Fermi surface reconstruction

{T}_{c}

Ising Nematic Quantum Critical Point in a Metal: A Monte Carlo Study

is found in a region of the phase diagram where the antiferromagnetic transition temperature extrapolates to zero, signaling a putative quantum critical point. The elucidation of the interplay between these two phenomena---high-

Is charge order induced near an antiferromagnetic quantum critical point

{T}_{c}

Non-Fermi-liquid at (2+1)d ferromagnetic quantum critical point

superconductivity and magnetic quantum criticality---remains an important piece of the complex puzzle of unconventional superconductivity. In this paper, we combine sign-problem-free quantum Monte Carlo simulations and field-theoretical analytical calculations to unveil the microscopic mechanism responsible for the superconducting instability of a general low-energy model, called the spin-fermion model. In this approach, low-energy electronic states interact with each other via the exchange of quantum critical magnetic fluctuations. We find that even in the regime of moderately strong interactions, both the superconducting transition temperature and the pairing susceptibility are governed not by the properties of the entire Fermi surface, but instead by the properties of small portions of the Fermi surface called hot spots. Moreover,