Orthogonal metal in the Hubbard model with liberated slave spins

Abstract

A two-dimensional Falicov-Kimball model, equivalent to the Hubbard model in an unconstrained slave-spin representation, is studied by quantum Monte Carlo simulations. The focus is on a fractionalized metallic phase that is characterized in terms of spectral, thermodynamic, and transport properties, including a comparison to the half-filled Hubbard model. The properties of this phase, most notably a single-particle gap but gapless spin and charge excitations, can in principle be understood in the framework of orthogonal metals. However, important and interesting differences arise in the present setting compared to single-particle mean-field theories and other models. We also discuss the role of the local constraints from the slave-spin representation within an extended phase diagram that includes the spatial dimension as a parameter, thereby making contact with previous work in infinite dimensions. Finally, we provide arguments for the absence of π-flux configurations and hence topologically ordered fractional phases in consistent mean-field slave-spin descriptions. arXiv:1906.11937v1 [cond-mat.str-el]

Metal to Orthogonal Metal Transition

“…We also notice the similarity of our OM phase with that discovered in recent works [28,36,37]. The Higgs transition between NM and OM in this work is replaced with a finite temperature crossover in Refs.…”

“…Together with works such as Ref. [36,37] where a similar OM state is discovered at finite temperature and Refs. [34,[44][45][46] where the deconfinement-confinement transition of the Dirac fermions are revealed and Ref.…”

“…The Higgs transition between NM and OM in this work is replaced with a finite temperature crossover in Refs. [36,37], as in the latter, the system behave as a conventional square lattice Hubbard model at low temperature. Also, in Ref.…”

The ALF (Algorithms for Lattice Fermions) project release 2.3. Documentation for the auxiliary-field quantum Monte Carlo code

“…The auxiliary-field quantum Monte Carlo (QMC) approach is the algorithm of choice to simulate thermodynamic properties of a variety of correlated electron systems in the solid state and beyond [1][2][3][4][5][6]. Apart from the physics of the canonical Hubbard model [7,8], the topics one can investigate in detail include correlation effects in the bulk and on surfaces of topological insulators [9][10][11][12], quantum phase transitions between Dirac fermions and insulators [13][14][15][16][17][18][19][20], deconfined quantum critical points [18,[21][22][23][24], constrained and unconstrained lattice gauge theories [21,[25][26][27][28][29][30], heavy fermion systems [31][32][33][34][35][36], nematic [37,38] and magnetic [39,40] quantum phase transitions in metals, antiferromagnetism in metals [41], superconductivity in spin-orbit split and in topological flat bands [42]…”

“…Aspects of this Hamiltonian were investigated in Refs. [21,25,26,[28][29][30] and we refer the interested user to these papers for a discussion of the phases and phase transitions supported by the model.…”