Hao Zhang
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Previous Organizations / Institutes
The organizations / institutes from the scholar's other articles in the past ten years
Research Subjects
Hao Zhang has a total of 9 co-authors. Here are the top co-authors by number of shared publications:
- Carlos Alberto Lamas
IFLP - CONICET, Departamento de Física, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, C.C. 67, 1900 La Plata, Argentina
6 shared publications M. Arlego
IFLP-CONICET, Departamento de Física, Universidad Nacional de La Plata, Casilla de Correo 67, 1900 La Plata, Argentina
4 shared publications- Wolfram Brenig
Institute for Theoretical Physics Technical University D-38106 Braunschweig Braunschweig Germany
4 shared publications C. A. Lamas
2 shared publicationsMarcelo Arlego
IFLP, UNLP, CONICET, Facultad de Ciencias Exactas, calle 49 y 115, La Plata, Argentina
2 shared publicationsC A Lamas
National Scientific and Technical Research Council
1 shared publication
Latest Publications
- Open Access
- 14 June 2018
- Published by American Physical Society (APS) in Physical Review B
- Vol. 97 (23) , 235123
Nematic quantum phases in the bilayer honeycomb antiferromagnet
The spin- Heisenberg antiferromagnet on the honeycomb bilayer lattice is shown to display a rich variety of semiclassical and genuinely quantum phases, controlled by the interplay between intralayer frustration and interlayer exchange. Employing a complementary set of techniques, comprising spin rotationally invariant Schwinger boson mean-field theory, bond operators, and series expansions, we unveil the quantum phase diagram, analyzing low-energy excitations and order parameters. By virtue of Schwinger bosons we scan the complete range of exchange parameters, covering both long-range-ordered and quantum disordered ground states, and reveal the existence of an extended, frustration-induced lattice nematic phase in a range of intermediate exchange unexplored so far.- 14 June 2018
- Published by American Physical Society (APS) in Physical Review B
- Vol. 97 (23) , 235123
Open AccessNematic quantum phases in the bilayer honeycomb antiferromagnet
The spin- Heisenberg antiferromagnet on the honeycomb bilayer lattice is shown to display a rich variety of semiclassical and genuinely quantum phases, controlled by the interplay between intralayer frustration and interlayer exchange. Employing a complementary set of techniques, comprising spin rotationally invariant Schwinger boson mean-field theory, bond operators, and series expansions, we unveil the quantum phase diagram, analyzing low-energy excitations and order parameters. By virtue of Schwinger bosons we scan the complete range of exchange parameters, covering both long-range-ordered and quantum disordered ground states, and reveal the existence of an extended, frustration-induced lattice nematic phase in a range of intermediate exchange unexplored so far. - Open Access
Nematic quantum phases in the bilayer honeycomb antiferromagnet
The spin$-1/2$ Heisenberg antiferromagnet on the honeycomb bilayer lattice is shown to display a rich variety of semiclassical and genuinely quantum phases, controlled by the interplay between intralayer frustration and interlayer exchange. Employing a complementary set of techniques, comprising spin rotationally invariant Schwinger boson mean field theory, bond operators, and series expansions we unveil the quantum phase diagram, analyzing low-energy excitations and order parameters. By virtue of Schwinger bosons we scan the complete range of exchange parameters, covering both long range ordered as well as quantum disordered ground states and reveal the existence of an extended, frustration induced lattice nematic phase in a range of intermediate exchange unexplored so far.
Open AccessNematic quantum phases in the bilayer honeycomb antiferromagnet
The spin$-1/2$ Heisenberg antiferromagnet on the honeycomb bilayer lattice is shown to display a rich variety of semiclassical and genuinely quantum phases, controlled by the interplay between intralayer frustration and interlayer exchange. Employing a complementary set of techniques, comprising spin rotationally invariant Schwinger boson mean field theory, bond operators, and series expansions we unveil the quantum phase diagram, analyzing low-energy excitations and order parameters. By virtue of Schwinger bosons we scan the complete range of exchange parameters, covering both long range ordered as well as quantum disordered ground states and reveal the existence of an extended, frustration induced lattice nematic phase in a range of intermediate exchange unexplored so far.
- Open Access
- 27 June 2016
- Published by American Physical Society (APS) in Physical Review B
- Vol. 93 (23) , 235150
Quantum phase diagram of a frustrated antiferromagnet on the bilayer honeycomb lattice
We study the spin-1/2 Heisenberg antiferromagnet on a bilayer honeycomb lattice including interlayer frustration. Using a set of complementary approaches, namely, Schwinger bosons, dimer series expansion, bond operators, and exact diagonalization, we map out the quantum phase diagram. Analyzing ground-state energies and elementary excitation spectra, we find four distinct phases, corresponding to three collinear magnetic long-range ordered states, and one quantum disordered interlayer dimer phase. We detail that the latter phase is adiabatically connected to an exact singlet product ground state of the bilayer, which exists along a line of maximum interlayer frustration. The order within the remaining three phases will be clarified.
- 27 June 2016
- Published by American Physical Society (APS) in Physical Review B
- Vol. 93 (23) , 235150
Open AccessQuantum phase diagram of a frustrated antiferromagnet on the bilayer honeycomb lattice
We study the spin-1/2 Heisenberg antiferromagnet on a bilayer honeycomb lattice including interlayer frustration. Using a set of complementary approaches, namely, Schwinger bosons, dimer series expansion, bond operators, and exact diagonalization, we map out the quantum phase diagram. Analyzing ground-state energies and elementary excitation spectra, we find four distinct phases, corresponding to three collinear magnetic long-range ordered states, and one quantum disordered interlayer dimer phase. We detail that the latter phase is adiabatically connected to an exact singlet product ground state of the bilayer, which exists along a line of maximum interlayer frustration. The order within the remaining three phases will be clarified.
- Open Access
Quantum phase diagram of a frustrated antiferromagnet on the bilayer honeycomb lattice
We study the spin-1/2 Heisenberg antiferromagnet on a bilayer honeycomb lattice including interlayer frustration. Using a set of complementary approaches, namely Schwinger bosons, dimer series expansion, bond operators, and exact diagonalization, we map out the quantum phase diagram. Analyzing ground state energies and elementary excitation spectra, we find four distinct phases, corresponding to three collinear magnetic long range ordered states, and one quantum disordered interlayer dimer phase. We detail, that the latter phase is adiabatically connected to an "exact" singlet product ground state of the the bilayer which exists along a line of maximum interlayer frustration. The order within the remaining three phases will be clarified.
Open AccessQuantum phase diagram of a frustrated antiferromagnet on the bilayer honeycomb lattice
We study the spin-1/2 Heisenberg antiferromagnet on a bilayer honeycomb lattice including interlayer frustration. Using a set of complementary approaches, namely Schwinger bosons, dimer series expansion, bond operators, and exact diagonalization, we map out the quantum phase diagram. Analyzing ground state energies and elementary excitation spectra, we find four distinct phases, corresponding to three collinear magnetic long range ordered states, and one quantum disordered interlayer dimer phase. We detail, that the latter phase is adiabatically connected to an "exact" singlet product ground state of the the bilayer which exists along a line of maximum interlayer frustration. The order within the remaining three phases will be clarified.
- Open Access
- 8 December 2014
- Published by IOP Publishing in Journal of Physics: Conference Series
- Vol. 568 (4)
Self consistent study of the quantum phases in a frustrated antiferromagnet on the bilayer honeycomb lattice
- 8 December 2014
- Published by IOP Publishing in Journal of Physics: Conference Series
- Vol. 568 (4)
Open AccessSelf consistent study of the quantum phases in a frustrated antiferromagnet on the bilayer honeycomb lattice
- Open Access
Quantum phases in the frustrated Heisenberg model on the bilayer honeycomb lattice
We use a combination of analytical and numerical techniques to study the phase diagram of the frustrated Heisenberg model on the bilayer honeycomb lattice. Using the Schwinger boson description of the spin operators followed by a mean field decoupling, the magnetic phase diagram is studied as a function of the frustration coupling $J_{2}$ and the interlayer coupling $J_{\bot}$. The presence of both magnetically ordered and disordered phases is investigated by means of the evaluation of ground-state energy, spin gap, local magnetization and spin-spin correlations. We observe a phase with a spin gap and short range N\'eel correlations that survives for non-zero next-nearest-neighbor interaction and interlayer coupling. Furthermore, we detect signatures of a reentrant behavior in the melting of N\'eel phase and symmetry restoring when the system undergoes a transition from an on-layer nematic valence bond crystal phase to an interlayer valence bond crystal phase. We complement our work with exact diagonalization on small clusters and dimer-series expansion calculations, together with a linear spin wave approach to study the phase diagram as a function of the spin $S$, the frustration and the interlayer couplings.Open AccessQuantum phases in the frustrated Heisenberg model on the bilayer honeycomb lattice
We use a combination of analytical and numerical techniques to study the phase diagram of the frustrated Heisenberg model on the bilayer honeycomb lattice. Using the Schwinger boson description of the spin operators followed by a mean field decoupling, the magnetic phase diagram is studied as a function of the frustration coupling $J_{2}$ and the interlayer coupling $J_{\bot}$. The presence of both magnetically ordered and disordered phases is investigated by means of the evaluation of ground-state energy, spin gap, local magnetization and spin-spin correlations. We observe a phase with a spin gap and short range N\'eel correlations that survives for non-zero next-nearest-neighbor interaction and interlayer coupling. Furthermore, we detect signatures of a reentrant behavior in the melting of N\'eel phase and symmetry restoring when the system undergoes a transition from an on-layer nematic valence bond crystal phase to an interlayer valence bond crystal phase. We complement our work with exact diagonalization on small clusters and dimer-series expansion calculations, together with a linear spin wave approach to study the phase diagram as a function of the spin $S$, the frustration and the interlayer couplings. - Open Access
- 6 January 2014
- Published by American Physical Society (APS) in Physical Review B
- Vol. 89 (2)
Quantum phases in the frustrated Heisenberg model on the bilayer honeycomb lattice
We use a combination of analytical and numerical techniques to study the phase diagram of the frustrated Heisenberg model on the bilayer honeycomb lattice. Using the Schwinger-boson description of the spin operators followed by a mean-field decoupling, the magnetic phase diagram is studied as a function of the frustration coupling ${J}_{2}$ and the interlayer coupling ${J}_{$\perp${}}$. The presence of both magnetically ordered and disordered phases is investigated by means of the evaluation of ground-state energy, spin gap, local magnetization, and spin-spin correlations. We observe a phase with a spin gap and short-range N\'eel correlations that survives for nonzero next-nearest-neighbor interaction and interlayer coupling. Furthermore, we detect signatures of a reentrant behavior in the melting of the N\'eel phase and symmetry restoring when the system undergoes a transition from an on-layer nematic valence-bond crystal phase to an interlayer valence-bond crystal phase. We complement our work with exact diagonalization on small clusters and dimer-series expansion calculations, together with a linear spin-wave approach to study the phase diagram as a function of the spin $S$, the frustration, and the interlayer couplings.- 6 January 2014
- Published by American Physical Society (APS) in Physical Review B
- Vol. 89 (2)
Open AccessQuantum phases in the frustrated Heisenberg model on the bilayer honeycomb lattice
We use a combination of analytical and numerical techniques to study the phase diagram of the frustrated Heisenberg model on the bilayer honeycomb lattice. Using the Schwinger-boson description of the spin operators followed by a mean-field decoupling, the magnetic phase diagram is studied as a function of the frustration coupling ${J}_{2}$ and the interlayer coupling ${J}_{$\perp${}}$. The presence of both magnetically ordered and disordered phases is investigated by means of the evaluation of ground-state energy, spin gap, local magnetization, and spin-spin correlations. We observe a phase with a spin gap and short-range N\'eel correlations that survives for nonzero next-nearest-neighbor interaction and interlayer coupling. Furthermore, we detect signatures of a reentrant behavior in the melting of the N\'eel phase and symmetry restoring when the system undergoes a transition from an on-layer nematic valence-bond crystal phase to an interlayer valence-bond crystal phase. We complement our work with exact diagonalization on small clusters and dimer-series expansion calculations, together with a linear spin-wave approach to study the phase diagram as a function of the spin $S$, the frustration, and the interlayer couplings. - Open Access
- 22 January 2013
- Published by American Physical Society (APS) in Physical Review B
- Vol. 87 (2)
Exotic disordered phases in the quantum-model on the honeycomb latticeWe study the ground-state phase diagram of the frustrated quantum ${J}_{1}$-${J}_{2}$ Heisenberg antiferromagnet on the honeycomb lattice using a mean-field approach in terms of the Schwinger boson representation of the spin operators. We present results for the ground-state energy, local magnetization, energy gap, and spin-spin correlations. The system shows magnetic long-range order for $0$\leqslant${}{J}_{2}/{J}_{1}$\lesssim${}0.2075$ (N\'eel) and $0.398$\lesssim${}{J}_{2}/{J}_{1}$\leqslant${}0.5$ (spiral). In the intermediate region, we find two magnetically disordered phases: a gapped spin liquid phase, which shows short-range N\'eel correlations $(0.2075$\lesssim${}{J}_{2}/{J}_{1}$\lesssim${}0.3732)$, and a lattice nematic phase $(0.3732$\lesssim${}{J}_{2}/{J}_{1}$\lesssim${}0.398)$, which is magnetically disordered but breaks lattice rotational symmetry. The errors in the values of the phase boundaries, which are implicit in the number of significant figures quoted, correspond purely to the error in the extrapolation of our finite-size results to the thermodynamic limit.- 22 January 2013
- Published by American Physical Society (APS) in Physical Review B
- Vol. 87 (2)
Open AccessExotic disordered phases in the quantum-model on the honeycomb latticeWe study the ground-state phase diagram of the frustrated quantum ${J}_{1}$-${J}_{2}$ Heisenberg antiferromagnet on the honeycomb lattice using a mean-field approach in terms of the Schwinger boson representation of the spin operators. We present results for the ground-state energy, local magnetization, energy gap, and spin-spin correlations. The system shows magnetic long-range order for $0$\leqslant${}{J}_{2}/{J}_{1}$\lesssim${}0.2075$ (N\'eel) and $0.398$\lesssim${}{J}_{2}/{J}_{1}$\leqslant${}0.5$ (spiral). In the intermediate region, we find two magnetically disordered phases: a gapped spin liquid phase, which shows short-range N\'eel correlations $(0.2075$\lesssim${}{J}_{2}/{J}_{1}$\lesssim${}0.3732)$, and a lattice nematic phase $(0.3732$\lesssim${}{J}_{2}/{J}_{1}$\lesssim${}0.398)$, which is magnetically disordered but breaks lattice rotational symmetry. The errors in the values of the phase boundaries, which are implicit in the number of significant figures quoted, correspond purely to the error in the extrapolation of our finite-size results to the thermodynamic limit. - Open AccessExotic disordered phases in the quantum $J_1-J_2$ model on the honeycomb latticeWe study the ground-state phase diagram of the frustrated quantum $J_1-J_2$ Heisenberg antiferromagnet on the honeycomb lattice using a mean field approach in terms of the Schwinger boson representation of the spin operators. We present results for the ground-state energy, local magnetization, energy gap and spin-spin correlations. The system shows magnetic long range order for $0\leq J_{2}/J_{1}\lesssim 0.2075$ (N\'eel) and $0.398\lesssim J_{2}/J_{1}\leq 0.5$ (spiral). In the intermediate region, we find two magnetically disordered phases: a gapped spin liquid phase which shows short-range N\'eel correlations $(0.2075 \lesssim J_{2}/J_{1} \lesssim 0.3732)$, and a lattice nematic phase $(0.3732 \lesssim J_{2}/J_{1}\lesssim 0.398)$, which is magnetically disordered but breaks lattice rotational symmetry. The errors in the values of the phase boundaries which are implicit in the number of significant figures quoted, correspond purely to the error in the extrapolation of our finite-size results to the thermodynamic limit.Open AccessExotic disordered phases in the quantum $J_1-J_2$ model on the honeycomb latticeWe study the ground-state phase diagram of the frustrated quantum $J_1-J_2$ Heisenberg antiferromagnet on the honeycomb lattice using a mean field approach in terms of the Schwinger boson representation of the spin operators. We present results for the ground-state energy, local magnetization, energy gap and spin-spin correlations. The system shows magnetic long range order for $0\leq J_{2}/J_{1}\lesssim 0.2075$ (N\'eel) and $0.398\lesssim J_{2}/J_{1}\leq 0.5$ (spiral). In the intermediate region, we find two magnetically disordered phases: a gapped spin liquid phase which shows short-range N\'eel correlations $(0.2075 \lesssim J_{2}/J_{1} \lesssim 0.3732)$, and a lattice nematic phase $(0.3732 \lesssim J_{2}/J_{1}\lesssim 0.398)$, which is magnetically disordered but breaks lattice rotational symmetry. The errors in the values of the phase boundaries which are implicit in the number of significant figures quoted, correspond purely to the error in the extrapolation of our finite-size results to the thermodynamic limit.
- 17 March 2009
- Published by IOP Publishing in Journal of Physics: Condensed Matter
- Vol. 21 (15) , 155501
Spin transport properties of a quantum dot coupled to ferromagnetic leads with noncollinear magnetizations
A correct general formula for the spin current through an interacting quantum dot coupled to ferromagnetic leads with magnetization at an arbitrary angle θ is derived within the framework of the Keldysh formalism. Under asymmetric conditions, the spin current component J(z) may change sign for 0<θ<π. It is shown that the spin current and spin tunneling magnetoresistance exhibit different angle dependence in the free and Coulomb blockade regimes. In the latter case, the competition of the spin precession and the spin-valve effect could lead to an anomaly in the angle dependence of the spin current.
- 17 March 2009
- Published by IOP Publishing in Journal of Physics: Condensed Matter
- Vol. 21 (15) , 155501
Spin transport properties of a quantum dot coupled to ferromagnetic leads with noncollinear magnetizations
A correct general formula for the spin current through an interacting quantum dot coupled to ferromagnetic leads with magnetization at an arbitrary angle θ is derived within the framework of the Keldysh formalism. Under asymmetric conditions, the spin current component J(z) may change sign for 0<θ<π. It is shown that the spin current and spin tunneling magnetoresistance exhibit different angle dependence in the free and Coulomb blockade regimes. In the latter case, the competition of the spin precession and the spin-valve effect could lead to an anomaly in the angle dependence of the spin current.