Phase diagram of a symmetric electron–hole bilayer system: a variational Monte Carlo study

Abstract

We study the phase diagram of a symmetric electron-hole bilayer system at absolute zero temperature and in zero magnetic field within the quantum Monte Carlo approach. In particular, we conduct variational Monte Carlo simulations for various phases, i.e. the paramagnetic fluid phase, the ferromagnetic fluid phase, the anti-ferromagnetic Wigner crystal phase, the ferromagnetic Wigner crystal phase and the excitonic phase, to estimate the ground-state energy at different values of in-layer density and inter-layer spacing. Slater-Jastrow style trial wave functions, with single-particle orbitals appropriate for different phases, are used to construct the phase diagram in the (r , d) plane by finding the relative stability of trial wave functions. At very small layer separations, we find that the fluid phases are stable, with the paramagnetic fluid phase being particularly stable at [Formula: see text] and the ferromagnetic fluid phase being particularly stable at [Formula: see text]. As the layer spacing increases, we first find that there is a phase transition from the ferromagnetic fluid phase to the ferromagnetic Wigner crystal phase when d reaches 0.4 a.u. at r = 20, and before there is a return to the ferromagnetic fluid phase when d approaches 1 a.u. However, for r < 20 and [Formula: see text] a.u., the excitonic phase is found to be stable. We do not find that the anti-ferromagnetic Wigner crystal is stable over the considered range of r and d. We also find that as r increases, the critical layer separations for Wigner crystallization increase.

Ground-state properties of electron-electron biwire systems

“…Two-dimensional systems of coupled, parallel quantum layers (electron-electron or electron-hole bilayers) show many unique phenomena [26][27][28][29][30][31][32]. Similarly, in 1D systems the additional interaction between charge carriers residing in different wires yields quantum properties such * sharmarajesh0387@gmail.com as non-Abelian topological phases (edge properties) [33][34][35][36][37], Coulomb drag between wires [38][39][40], nonadditive dispersion [41][42][43][44], enhancement in the onset of Wigner crystallization [45], and formation of biexcitons [46][47][48].…”

Sign-Free Determinant Quantum Monte Carlo Study of Excitonic Density Orders in a Two-Orbital Hubbard-Kanamori Model

“…An exciton is a bosonic bound state of an electron and a hole, which can undergo Bose-Einstein condensation below a critical temperature [13,14] to form an excitonic superfluid. Extensive early studies have analyzed excitonic condensation and bi-exciton formation in bilayer quantum wells and heterostructures with spatially-separated electrons and holes [15][16][17][18][19][20]. Meanwhile, studies of superconductivity in strongly correlated materials recently have motivated explorations of electron-hole counterparts in multi-layer lattice models [21][22][23][24][25][26][27][28][29].…”

Biexciton Condensation in Electron-Hole-Doped Hubbard Bilayers: A Sign-Problem-Free Quantum Monte Carlo Study

“…Specifically for excitonic ordering, spatial separation of electrons and holes into two layers was proposed to suppress electron-hole recombination [8]. Following this idea, excitonic order, including exciton condensation and biexciton formation, has been extensively studied in electron-hole bilayer continuous models, which describe systems with electrons and holes confined in quantum wells separated into two layers by a barrier [9][10][11][12][13][14]. As well, studies of superconductivity in strongly correlated materials recently have motivated exploration of the electron-hole counterpart in two-band Hubbard-like lattice models [15][16][17][18][19][20][21][22][23][24].…”