Itinerant Quantum Critical Point with Fermion Pockets and Hot Spots

Combining determinantal quantum Monte Carlo (DQMC) and elective momentum ultra-size quantum Monte Carlo (EQMC) methods, we systematically investigated the itinerant quantum critical point on a 2D square lattice with antiferromagnetic spin fluctuations at wavevector Q = (π, π). System sizes of 60×60×320 (L × L × Lτ) are comfortably accessed, and the quantum critical scaling behaviors are revealed with unprecedingly high precision. We found that the antiferromagnetic spin fluctuations introduce effective interactions among fermions and the fermions in return render the bare bosonic critical point into a new universality, different from the bare Ising universality class and the Hertz-Mills-Moriya RPA prediction. At the quantum critical point, a finite anomalous dimension η ∼ 0.125 is observed in the bosonic propagator, and fermions at hot spots evolve into a non-Fermiliquid. In the antiferromagnetically ordered metallic phase, fermion pockets are formed as energy gap opens up at the hot spots.