Quantum Phases in Two-Dimensional Frustrated Spin-1/2 Antiferromagnets

Sindzingre, Philippe; Lhuillier, C.; Fouet, J.-B.

doi:10.1142/9789812777843_0011

Cited by 5 publications

(6 citation statements)

References 22 publications

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“…33,34 The understanding of the low lying continuum of singlets is still incomplete but some progresses have been done in the last years. 37,38,39,40 Recent ED calculations 37 on a kagomé N = 24 sample depletted of two sites suggest that the elementary excitations likely consist of deconfined spinons: as shown in Fig 3, the spin-gap does not depend neither on the presence of the two nonmagnetic holes nor on their separation which suggest that spin-1/2 excitations are essentially free (un- confined). 41 The low lying singlets could be related to a family of short range RVB dimer coverings of the lattice.…”

Section: Type II Spin Liquidmentioning

confidence: 95%

Quantum Phases in Two-Dimensional Frustrated Spin-1/2 Antiferromagnets

Sindzingre

Lhuillier

Fouet

2003

Int. J. Mod. Phys. B

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Section: Type II Spin Liquidmentioning

confidence: 95%

Quantum Phases in Two-Dimensional Frustrated Spin-1/2 Antiferromagnets

Sindzingre

Lhuillier

Fouet

2003

Int. J. Mod. Phys. B

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“…Therefore a large amount of information on possible Néel like LRO is contained in the spectrum of HAFM on finite lattices. There are extensive systematic studies for HAFM on the square, triangular and kagomé lattice [31,[36][37][38][39]42] and some recent reviews by Lhuillier, Sindzingre, Fouet and Misguich [11][12][13][14][15]. We follow the lines of their studies and illustrate some main features using the HAFM on the square lattice as an example.…”

Section: Mechanism Of Symmetry Breaking -The Pisa Tower Of Quasi-dege...mentioning

confidence: 99%

“…At the end of this paragraph we will classify the magnetic ordering on the 11 Archimedean tilings using the four basic types of low-energy physics in 2D isotropic quantum antiferromagnets proposed and described recently by Lhuillier, Sindzingre, Fouet and Misguich [11][12][13][14][15]. The first type of GS phases is the semi-classical LRO (collinear or noncollinear).…”

Section: Summary and Comparisonmentioning

confidence: 99%

“…A more specific classification of GS phases of 2D quantum magnets has been proposed recently by Lhuillier, Sindzingre, Fouet and Misguich [11][12][13][14][15]. Besides the semi-classical Néel like LRO, these authors also characterize three quantum GS phases, namely the so-called valence bond crystal, the type I spin liquid and the type II spin liquid (for more details see [11][12][13][14][15] and also section 4.4).…”

Section: Introductionmentioning

confidence: 99%

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Quantum magnetism in two dimensions: From semi-classical Néel order to magnetic disorder

Richter

Schulenburg

Honecker

2004

Lecture Notes in Physics

181

275

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In this article we focus on the ground state and the low-lying excitations of the s = 1/2 Heisenberg antiferromagnet (HAFM) on the 11 two-dimensional (2D) uniform Archimedean lattices.Although we know from the Mermin-Wagner theorem that thermal fluctuations are strong enough to destroy magnetic long-range order (LRO) for Heisenberg spin systems at any finite temperature in one and two dimensions, the role of quantum fluctuations is less understood. While the ground state of the one-dimensional (1D) quantum HAFM is not long-range ordered, the quantum HAFM e.g. on the 2D square and triangular lattices exhibits semiclassical Néel like LRO. However, in two dimensions there are many other lattices with different coordination numbers and topologies, and there is no general statement concerning zero-temperature Néel-like LRO. Recent experimental results on CaV 4 O 9 and SrCu 2 (BO 3 ) 2 demonstrate the possibility of non-Néel ordered ground states and signal that the s = 1/2 HAFM on 2D lattices with appropriate topology may have a ground state without semiclassical LRO.Based on extensive large-scale exact diagonalization studies of the ground state and the low-lying excitations for the spin-1/2 HAFM on the Archimedean lattices we compare and discuss the ground-state features of all 11 lattices. 2 Richter, Schulenburg, and HoneckerIn this manner we obtain some insight in the influence of lattice topology on magnetic ordering of quantum antiferromagnets in two dimensions. From our results we conclude that the ground state of the spin-1/2 HAFM on most of the Archimedean lattices (in particular the four bipartite ones) turns out to be semi-classically Néel-like ordered. However, we find that the interplay of competition of bonds (geometric frustration and non-equivalent nearest neighbor bonds) and quantum fluctuations gives rise to a quantum paramagnetic ground state without semi-classical LRO for two lattices. The first one is the famous kagomé lattice, for which this statement is well-known by numerous studies during the last decade. Remarkably, we find one additional lattice among the 11 uniform Archimedean lattices, the so-called star lattice, with a quantum paramagnetic ground state. For both these Archimedean lattices the ground state is highly degenerate in the classical limit s → ∞, although notably their quantum ground states are fundamentally different.Furthermore, we present numerical results for the magnetization curve of the HAFM on all 11 Archimedean lattices. The magnetization process is discussed in some detail for the square, triangular and kagomé lattices. One focus are plateaus appearing in the magnetization curve due to quantum fluctuations and geometric frustration. In particular, the kagomé lattice exhibits a rich spectrum of magnetization plateaus. Another focus are magnetization jumps arising on the kagomé and the star lattice just below the saturation field. These magnetization jumps may be understood analytically by using independent local magnon excitations.Some related s = 1/2 models are also dis...

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“…It essentially takes the basic Hartree–Fock molecular orbital method and constructs multi-electron wave functions using the exponential cluster operator to account for electron correlation and dispersion. This method has been used by some of the most accurate calculations for small- to medium-sized molecules (Agarwal et al, 2009 ; Cramer & Bickelhaupt, 2003 ; Scuseria & Schaefer III, 1989 ; Scuseria, Janssen, & Schaefer, 1988 ; Sindzingre, Lhuillier, & Fouet, 2001 ). On the other hand, since the Hp– π bond length (~2.5 Å) is much longer than the common hydrogen bonds (~2.0 Å), large basis sets are necessary, including the polarization functions, diffuse functions, and floating functions.…”

Section: Methods and Theorymentioning

confidence: 99%

Insight into a molecular interaction force supporting peptide backbones and its implication to protein loops and folding

Chen²,

Xie

et al. 2014

Journal of Biomolecular Structure and Dynamics

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Although not being classified as the most fundamental protein structural elements like α-helices and β-strands, the loop segment may play considerable roles for protein stability, flexibility, and dynamic activity. Meanwhile, the protein loop is also quite elusive; i.e. its interactions with the other parts of protein as well as its own shape-maintaining forces have still remained as a puzzle or at least not quite clear yet. Here, we report a molecular force, the so-called polar hydrogen–π interaction (Hp–π), which may play an important role in supporting the backbones of protein loops. By conducting the potential energy surface scanning calculations on the quasi π-plane of peptide bond unit, we have observed the following intriguing phenomena: (1) when the polar hydrogen atom of a peptide unit is perpendicularly pointing to the π-plane of other peptide bond units, a remarkable Hp–π interaction occurs; (2) the interaction is distance and orientation dependent, acting in a broad space, and belonging to the ‘point-to-plane’ one. The molecular force reported here may provide useful interaction concepts and insights into better understanding the loop’s unique stability and flexibility feature, as well as the driving force of the protein global folding.

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Quantum Phases in Two-Dimensional Frustrated Spin-1/2 Antiferromagnets

Cited by 5 publications

References 22 publications

Quantum Phases in Two-Dimensional Frustrated Spin-1/2 Antiferromagnets

Quantum Phases in Two-Dimensional Frustrated Spin-1/2 Antiferromagnets

Quantum magnetism in two dimensions: From semi-classical Néel order to magnetic disorder

Insight into a molecular interaction force supporting peptide backbones and its implication to protein loops and folding

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