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We construct a class of projected entangled pair states which is exactly the resonating valence bond wave functions endowed with both short range and long range valence bonds. With an energetically preferred resonating valence bond pattern, the wave function is simplified to live in a one-parameter variational space. We tune this variational parameter to minimize the energy for the frustrated spin-1/2 J(1)-J(2) antiferromagnetic Heisenberg model on the square lattice. Taking a cylindrical geometry, we are able to construct four topological sectors with an even or odd number of fluxes penetrating the cylinder and an even or odd number of spinons on the boundary. The energy splitting in different topological sectors is exponentially small with the cylinder perimeter. We find a power law decay of the dimer correlation function on a torus, and a lnL correction to the entanglement entropy, indicating a gapless spin-liquid phase at the optimum parameter.
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http://dx.doi.org/10.1103/PhysRevLett.111.037202 | DOI Listing |
Phys Rev Lett
August 2025
University of California, Department of Physics, Santa Barbara, California 93106, USA.
We demonstrate that, starting with a simple fermion wave function, the steady mixed state of the evolution of a class of Lindbladians, and the ensemble created by strong local measurement of fermion density without postselection can be mapped to the "Gutzwiller projected" wave functions in the doubled Hilbert space-the representation of the density matrix through the Choi-Jamiołkowski isomorphism. A Gutzwiller projection is a broadly used approach of constructing spin liquid states. For example, if one starts with a gapless free Dirac fermion pure quantum state, the constructed mixed state corresponds to an algebraic spin liquid in the doubled Hilbert space.
View Article and Find Full Text PDFPhys Rev Lett
June 2025
Julius-Maximilians-Universität, Institut für Theoretische Physik und Astrophysik and Würzburg-Dresden Cluster of Excellence ct.qmat, 97074 Würzburg, Germany.
We analyze the Kitaev model on the {9,3} hyperbolic lattice. The {9,3} is formed by a regular tricoordinated tiling of nonagons, where the three-color coding of bonds according to the inequivalent Kitaev Ising spin couplings yields the natural generalization of the original Kitaev model for Euclidean regular honeycomb tiling. Upon investigation of the bulk spectrum for large finite size droplets, we identify a gapless chiral Z_{2} spin liquid state featuring spontaneous time-reversal symmetry breaking.
View Article and Find Full Text PDFNat Commun
April 2025
Department of Physics, University of Virginia, Charlottesville, VA, 22904, USA.
The pursuit of quantum spin liquid (QSL) states in condensed matter physics has drawn attention to kagome antiferromagnets (AFM) where a two-dimensional corner-sharing network of triangles frustrates conventional magnetic orders. While quantum kagome AFMs based on Cu (3d, s = ½) ions have been extensively studied, there is so far little work beyond copper-based systems. Here we present our bulk magnetization, specific heat and neutron scattering studies on single crystals of a new titanium fluorides CsRbKTiF where Ti (3d, s = ½) ions form a modulated quantum kagome antiferromagnet that does not order magnetically down to 1.
View Article and Find Full Text PDFPhys Rev Lett
March 2025
Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan.
Kitaev quantum spin liquids (KSLs) in layered honeycomb magnets are known to host Majorana quasiparticles, whose excitations depend strongly on the direction of the applied magnetic field. In the high-field phase of α-RuCl_{3}, specific heat measurements have revealed characteristic field-angle dependence of low-energy excitations consistent with the Kitaev model, providing bulk evidence for the KSL state. Here we present low-temperature measurements of specific heat C(T) for another KSL candidate Na_{2}Co_{2}TeO_{6} (NCTO) under field rotation within the honeycomb plane.
View Article and Find Full Text PDFChem Sci
April 2025
Songshan Lake Materials Laboratory Dongguan Guangdong Province 523808 China
Alkali-metal doped polyaromatic hydrocarbons (PAHs) have shown great potential in realizing exotic states of matter such as quantum spin liquids (QSLs). However, it is challenging to obtain new pure-phase candidates and perform experimental identifications accordingly. Here, we report the discovery and characterization of Cs(chrysene˙)(THF)·(THF) (1, THF = tetrahydrofuran), a pure-phase spin-½ organic magnet composed of triangular-based zig-zag magnetic layers, which give rise to strong spin frustration.
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