Spin 1/2 1D chains are ideal for realizations of quantum spin liquids (QSLs). Here we report the discovery of a QSL in Cs4CuSb2Cl12. Compared to previously reported S = 1/2 1D chains, it possesses a wider temperature range over which the QSL state is stabilized. We find Fermionic-like excitations extending from T = 0.8 K up to at least T = 5 K, with a large T-linear contribution to the specific heat, gamma = 31.5(2) mJ mol-1 K-2. At T = 0.7 K, there is a second-order phase transition, reminiscent of a superconducting transition, with a specific heat jump of delta C / (gammaTc) = 0.8(1), that is unchanged by a 5 T magnetic field. Thus Cs4CuSb2Cl12 reveals new phenomenology deep in the 1D QSL regime.
The $\mathrm{spin}\text{\ensuremath{-}}\frac{1}{2}$ Heisenberg antiferromagnetic chain is ideal for realizing one of the simplest gapless quantum spin liquids (QSLs), supporting a many-body ground state whose elementary excitations are fractional fermionic excitations called spinons. Here we report the discovery of such a one-dimensional (1D) QSL in
Cs4CuSb2Cl12. Compared to previously reported
S=21 1D chains, this material possesses a wider temperature range over which the QSL state is stabilized. We identify spinon excitations extending at
T>0.8K, with a large
T-linear contribution to the specific heat, $\ensuremath{\gamma}=31.5(2)\phantom{\rule{0.16em}{0ex}}\mathrm{mJ}\phantom{\rule{0.16em}{0ex}}\mathrm{mo}{\mathrm{l}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}2}$, which contribute itinerantly to thermal transport up to temperatures as high as
T=35K. At
T=0.7K, we find a second-order phase transition that is unchanged by a ${\ensuremath{\mu}}_{0}H=5\phantom{\rule{0.16em}{0ex}}\mathrm{T}$ magnetic field.
Cs4CuSb2Cl12 reveals new phenomenology deep in the 1D QSL regime, supporting a gapped QSL phase over a wide temperature range compared to many other experimental realizations.
Recent studies have revealed that the randomness-induced quantum spin liquid (QSL)-like state is stabilized in certain frustrated quantum magnets in two and three dimensions. In order to clarify the nature of this gapless QSL-like state, we investigate both zero- and finite-temperature properties of the random-bond one-dimensional (1D)
s=12 Heisenberg model with the competing nearest-neighbor and next-nearest-neighbor antiferromagnetic interactions,
J1 and
J2, by means of the exact diagonalization, density-matrix renormalization-group and Hams--de Raedt methods. We find that, on increasing the frustration
J2, the gapless nonmagnetic state stabilized in the unfrustrated model with
J2=0, the {\it unfrustrated\} random-singlet (RS) state, exhibits a phase transition into different gapless nonmagnetic state, the {\it frustrated\} RS state. This frustrated RS state in 1D has properties quite similar to the randomness-induced QSL-like state recently identified in 2D and 3D frustrated magnets exhibiting the
T-linear low-temperature (
T) specific heat, while the unfrustrated RS state is more or less specific to the unfrustrated 1D system exhibiting the
∼1(logT)3 low-
T specific heat. Universal features and the robustness against perturbations of the frustrated RS state are emphasized.
We study in this paper quantum spin liquid states (QSLs) at the vicinity of the metal-insulator transition. Assuming that the low-energy excitations in the QSLs are labeled by ``spinon'' occupation numbers with the same Fermi surface structure as in the corresponding metal (Fermi-liquid) side, we propose a phenomenological Landau-like low-energy theory for the QSLs and show that the usual
U(1) QSLs is a representative member of this class of spin liquids. Based on our effective low-energy theory, an alternative picture to the Brinkman-Rice picture of the Mott metal-insulator transition is proposed. The charge, spin, and thermal responses of QSLs are discussed under such a phenomenology.
A quantum spin liquid (QSL) is an exotic insulating phase with emergent gauge fields and fractionalized excitations. However, the unambiguous demonstration of the existence of a QSL in a “nonengineered” microscopic model (or in any material) remains challenging. Here, using numerically exact sign-problem-free quantum Monte Carlo simulations, we show that a QSL arises in a nonengineered electron–phonon model. Specifically, we investigate the ground-state phase diagram of the bond Su–Schrieffer–Heeger model on a 2D triangular lattice at (one electron per site), which we show includes a QSL phase which is fully gapped, exhibits no symmetry-breaking order, and supports deconfined fractionalized holon excitations. This suggests promising routes for finding QSLs in realistic materials and high- T c superconductivity by lightly doping them.
Abstract Broad interest in quantum spin liquid (QSL) phases was triggered by the notion that they can be viewed as insulating phases with preexisting electron pairs, such that upon light doping they might automatically yield high temperature superconductivity. Yet despite intense experimental and numerical efforts, definitive evidence showing that doping QSLs leads to superconductivity has been lacking. We address the problem of a lightly doped QSL through a large-scale density-matrix renormalization group study of the t-J model on finite-circumference triangular cylinders with a small but nonzero concentration of doped holes. We provide direct evidences that doping QSL can naturally give rise to d-wave superconductivity. Specifically, we find power-law superconducting correlations with a Luttinger exponent, Ksc ≈ 1, which is consistent with a strongly diverging superconducting susceptibility,
χsc∼T−(2−Ksc) χ s c ~ T − ( 2 − K s c ) as the temperature T → 0. The spin–spin correlations—as in the undoped QSL state—fall exponentially which suggests that the superconducting pair-pair correlations evolve smoothly from the insulating parent state.
An exotic quantum spin liquid (QSL) is formed with such hypothetic particles as fermionic spinons carrying spin 1/2 and no charge. Here we calculate its thermodynamic and relaxation properties. Our calculations unveil the fundamental properties of QSL, forming a strongly correlated Fermi system located at a fermion condensation quantum phase transition. These are in good agreement with experimental data and allow us to detect the behavior of QSL as that observed in heavy-fermion metals. We predict that the thermal resistivity of QSL under the application of magnetic fields at fixed temperature demonstrates a very specific behavior. The key features of our findings are the presence of spin-charge separation and QSL formed with itinerant heavy spinons in herbertsmithite.