Ya-Hui Zhang - "Fractional Fermi Liquid from doping spin-triplet doublons..."

Full title: "Fractional Fermi Liquid from doping spin-triplet doublons and possible realization in Nickelate"
For the schedule of the Harvard/MIT CMT seminar: https://sites.google.com/view/harvardmitcmt/home

Abstract:
In this talk I will propose and study a new kind of t-J model. I will consider an unusual case for hole doping a spin 1/2 Mott insulator formed by d^9 state: the spin-triplet doublon (d^8 state ) has lower energy than the spin singlet doublon. This scenario can be potentially realized in transition metal oxide with large Hund’s coupling between the two e_g orbitals and with oxygen band far away from fermi energy, for example, in certain nickelate in which we dope S=1 Ni^{2+} into Mott insulator formed by S=1/2 Ni^{1+}. The low energy model is an unconventional t-J model with two spin 1/2 singly occupied states and three spin-triplet doublon states per site. We simulate the 1D version of this model by DMRG and find clear evidence of a 1D analog of fractional Fermi liquid (FL*) phase: a small pocket coexists with the spin liquid inherited from the Mott insulator, with a total central charge c=3. I will provide a theoretical description based on a three-fermion parton mean field theory with U(2) gauge structure. The theory can be easily generalized to high dimension and I will conjecture that a metal with small Fermi surface is a generic fate of this unusual t-J model. If time allowed, I will also show numerical evidence of a continuous quantum critical point in 1D between this FL* phase and the conventional phase with large Fermi surface. Across the transition there is a jump of total Fermi surface volume (or carrier density) by 1/2 .

Видео Ya-Hui Zhang - "Fractional Fermi Liquid from doping spin-triplet doublons..." канала harvard_mit_cmt_seminar