Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:0811.4745 · Physical Review Letters

Theory of the Field-Induced BEC in the Frustrated Spin- 1 2 Dimer Compound BaCuSi 2 O 6

Nicolas Laflorencie, Frédéric Mila

Published Feb 13, 2009• 34 citations
arXivHTMLPDF

Abstract

Building on recent neutron and NMR experiments, we investigate the field-induced exotic criticality observed in the frustrated compound BaCuSi2O6 using a frustrated model with two types of bilayers. A semiclassical treatment of the effective hard-core boson model shows that perfect interlayer frustration leads to a 2D-like critical exponent varphi=1 without logarithmic corrections and to a 3D low temperature phase with different but nonvanishing triplet populations in both types of bilayers. These further suggest a simple phenomenology in terms of a field-dependent transverse coupling in the context of which we reproduce the entire field-temperature phase diagram with quantum Monte Carlo simulations.

DOI
10.1103/physrevlett.102.060602

Related papers

Spatially resolved magnetization in the Bose-Einstein condensed state of BaCuSi 2 O 6 : Evidence for imperfect frustration

S. Krämer, Nicolas Laflorencie, Raivo Stern +5 more

In order to understand the nature of the two-dimensional Bose-Einstein condensed (BEC) phase in BaCuSi${}_{2}$O${}_{6}$, we performed detailed ${}^{63}$Cu and ${}^{29}$Si NMR above the critical magnetic field, ${H}_{c1}=23.4$ T. The two different alternating layers present in the system have very different local magnetizations close to ${H}_{c1}$; one is very weak, and its size and field dependence are highly sensitive to the nature of inter-layer coupling. Its precise value could only be determined by ``on-site'' ${}^{63}$Cu NMR, and the data are fully reproduced by a model of interacting hard-core bosons in which the perfect frustration associated to tetragonal symmetry is slightly lifted, leading to the conclusion that the population of the less populated layers is not fully incoherent but must be partially condensed.

arXiv:1212.3763•Physical Review B•May 23, 2013•17 citations

Field-controlled multicritical behavior and emergent universality in fully frustrated quantum magnets

Yuchen Fan, Ning Xi, Changle Liu +2 more

Abstract Phase transitions in condensed matter are a source of exotic emergent properties. We study the fully frustrated bilayer Heisenberg antiferromagnet to demonstrate that an applied magnetic field creates a previously unknown emergent criticality. The quantum phase diagram contains four states with distinctly different symmetries, all but one pair separated by first-order transitions. We show by quantum Monte Carlo simulations that the thermal phase diagram is dominated by a wall of discontinuities extending between the dimer-triplet phases and the singlet-containing phases. This wall is terminated at finite temperatures by a critical line, which becomes multicritical where the Berezinskii-Kosterlitz-Thouless (BKT) transition of the dimer-triplet antiferromagnet and the thermal Ising transition of the singlet-triplet crystal phase also terminate. The combination of merging symmetries leads to a 4-state Potts universality not contained in the microscopic Hamiltonian, which we interpret within the Ashkin-Teller model. Our results represent a systematic step in understanding emergent phenomena in quantum magnetic materials, including the “Shastry-Sutherland compound” SrCu2(BO3)2.

arXiv:2306.16288•npj Quantum Materials•Mar 9, 2024•7 citations

Field-induced quantum phases in a frustrated spin-dimer model: A sign-problem-free quantum Monte Carlo study

Kwai-Kong Ng, Min-Fong Yang

The magnetization process of a frustrated spin-1/2 spin-dimer model on a square lattice is investigated by means of a sign-problem-free quantum Monte Carlo algorithm developed recently. Rich field-induced quantum phases are discovered. We find two spin superfluids satisfying different symmetries upon layer permutation. There exist as well two solid phases with distinct checkerboard patterns. More interestingly, a spin supersolid phase possessing both solid and superfluid long-range orders is observed over a finite regime of magnetic fields. We find that this exotic phase can be stabilized only when small but nonzero spin anisotropy is present. Various field-induced transitions among these phases are explored. Our findings may provide guidance to the search of these interesting quantum phases in real frustrated spin-dimer compounds.

arXiv:1610.08741•Physical review. B./Physical review. B•Feb 28, 2017•22 citations

Quantum phase transitions in coupled dimer compounds

Omid Nohadani, Stefan Weßel, Stephan Haas

We study the critical properties in cubic systems of antiferromagnetically coupled spin dimers near magnetic-field-induced quantum phase transitions. The quantum critical points in the zero-temperature phase diagram are determined from quantum Monte Carlo simulations. Furthermore, scaling properties of the uniform magnetization and the staggered transverse magnetization across the quantum phase transition in magnetic fields are calculated. Excellent agreement is observed between the quantum Monte Carlo simulations and previous analytical and experimental results near the magnetic field-induced transition. At the zero-field quantum critical point, logarithmic corrections to mean-field behavior are observed, which match well recent experiments for the pressure-induced quantum phase transition.

arXiv:cond-mat/0411599•Physical Review B•Jul 19, 2005•46 citations

Multiple Magnon Modes and Consequences for the Bose-Einstein Condensed Phase in BaCuSi 2 O 6

Christian Rüegg, MCMORROW Desmond Francis, Bruce Normand +7 more

The compound BaCuSi2O6 is a quantum magnet with antiferromagnetic dimers of S=1/2 moments on a quasi-2D square lattice. We have investigated its spin dynamics by inelastic neutron scattering experiments on single crystals with an energy resolution considerably higher than in an earlier study. We observe multiple magnon modes, indicating clearly the presence of magnetically inequivalent dimer sites. The more complex spin Hamiltonian revealed in our study leads to a distinct form of magnon Bose-Einstein condensate phase with a spatially modulated condensate amplitude.

arXiv:cond-mat/0607465•Physical Review Letters•Jan 4, 2007•64 citations

Frustrated honeycomb-lattice bilayer quantum antiferromagnet in a magnetic field: Unconventional phase transitions in a two-dimensional isotropic Heisenberg model

Taras Krokhmalskii, Vasyl Baliha, Oleg Derzhko +2 more

We consider the spin-1/2 antiferromagnetic Heisenberg model on a bilayer honeycomb lattice including interlayer frustration in the presence of an external magnetic field. In the vicinity of the saturation field, we map the low-energy states of this quantum system onto the spatial configurations of hard hexagons on a honeycomb lattice. As a result, we can construct effective classical models (lattice-gas as well as Ising models) on the honeycomb lattice to calculate the properties of the frustrated quantum Heisenberg spin system in the low-temperature regime. We perform classical Monte Carlo simulations for a hard-hexagon model and adopt known results for an Ising model to discuss the finite-temperature order-disorder phase transition that is driven by a magnetic field at low temperatures. We also discuss an effective-model description around the ideal frustration case and find indications for a spin-flop-like transition in the considered isotropic spin model.

arXiv:1701.07876•Physical review. B./Physical review. B•Mar 13, 2017•17 citations
Building on recent neutron and NMR experiments, we investigate the field-induced exotic criticality observed in the frustrated compound BaCuSi2O6 using a frustrated model with two types of bilayers. A semiclassical treatment of the effective hard-core boson model shows that perfect interlayer frustration leads to a 2D-like critical exponent varphi=1 without logarithmic corrections and to a 3D low temperature phase with different but nonvanishing triplet populations in both types of bilayers. These further suggest a simple phenomenology in terms of a field-dependent transverse coupling in the context of which we reproduce the entire field-temperature phase diagram with quantum Monte Carlo simulations.
In order to understand the nature of the two-dimensional Bose-Einstein condensed (BEC) phase in BaCuSi2{}_{2}2​O6{}_{6}6​, we performed detailed 63{}^{63}63Cu and 29{}^{29}29Si NMR above the critical magnetic field, Hc1=23.4{H}_{c1}=23.4Hc1​=23.4 T. The two different alternating layers present in the system have very different local magnetizations close to Hc1{H}_{c1}Hc1​; one is very weak, and its size and field dependence are highly sensitive to the nature of inter-layer coupling. Its precise value could only be determined by ``on-site'' 63{}^{63}63Cu NMR, and the data are fully reproduced by a model of interacting hard-core bosons in which the perfect frustration associated to tetragonal symmetry is slightly lifted, leading to the conclusion that the population of the less populated layers is not fully incoherent but must be partially condensed.
Abstract Phase transitions in condensed matter are a source of exotic emergent properties. We study the fully frustrated bilayer Heisenberg antiferromagnet to demonstrate that an applied magnetic field creates a previously unknown emergent criticality. The quantum phase diagram contains four states with distinctly different symmetries, all but one pair separated by first-order transitions. We show by quantum Monte Carlo simulations that the thermal phase diagram is dominated by a wall of discontinuities extending between the dimer-triplet phases and the singlet-containing phases. This wall is terminated at finite temperatures by a critical line, which becomes multicritical where the Berezinskii-Kosterlitz-Thouless (BKT) transition of the dimer-triplet antiferromagnet and the thermal Ising transition of the singlet-triplet crystal phase also terminate. The combination of merging symmetries leads to a 4-state Potts universality not contained in the microscopic Hamiltonian, which we interpret within the Ashkin-Teller model. Our results represent a systematic step in understanding emergent phenomena in quantum magnetic materials, including the “Shastry-Sutherland compound” SrCu2(BO3)2.
The magnetization process of a frustrated spin-1/2 spin-dimer model on a square lattice is investigated by means of a sign-problem-free quantum Monte Carlo algorithm developed recently. Rich field-induced quantum phases are discovered. We find two spin superfluids satisfying different symmetries upon layer permutation. There exist as well two solid phases with distinct checkerboard patterns. More interestingly, a spin supersolid phase possessing both solid and superfluid long-range orders is observed over a finite regime of magnetic fields. We find that this exotic phase can be stabilized only when small but nonzero spin anisotropy is present. Various field-induced transitions among these phases are explored. Our findings may provide guidance to the search of these interesting quantum phases in real frustrated spin-dimer compounds.
We study the critical properties in cubic systems of antiferromagnetically coupled spin dimers near magnetic-field-induced quantum phase transitions. The quantum critical points in the zero-temperature phase diagram are determined from quantum Monte Carlo simulations. Furthermore, scaling properties of the uniform magnetization and the staggered transverse magnetization across the quantum phase transition in magnetic fields are calculated. Excellent agreement is observed between the quantum Monte Carlo simulations and previous analytical and experimental results near the magnetic field-induced transition. At the zero-field quantum critical point, logarithmic corrections to mean-field behavior are observed, which match well recent experiments for the pressure-induced quantum phase transition.
The compound BaCuSi2O6 is a quantum magnet with antiferromagnetic dimers of S=1/2 moments on a quasi-2D square lattice. We have investigated its spin dynamics by inelastic neutron scattering experiments on single crystals with an energy resolution considerably higher than in an earlier study. We observe multiple magnon modes, indicating clearly the presence of magnetically inequivalent dimer sites. The more complex spin Hamiltonian revealed in our study leads to a distinct form of magnon Bose-Einstein condensate phase with a spatially modulated condensate amplitude.
We consider the spin-1/2 antiferromagnetic Heisenberg model on a bilayer honeycomb lattice including interlayer frustration in the presence of an external magnetic field. In the vicinity of the saturation field, we map the low-energy states of this quantum system onto the spatial configurations of hard hexagons on a honeycomb lattice. As a result, we can construct effective classical models (lattice-gas as well as Ising models) on the honeycomb lattice to calculate the properties of the frustrated quantum Heisenberg spin system in the low-temperature regime. We perform classical Monte Carlo simulations for a hard-hexagon model and adopt known results for an Ising model to discuss the finite-temperature order-disorder phase transition that is driven by a magnetic field at low temperatures. We also discuss an effective-model description around the ideal frustration case and find indications for a spin-flop-like transition in the considered isotropic spin model.