Enhanced Intertwined Spin and Charge Orders in the t–J Model in a Small J Case

The one-band t–J model captures strong correlations in cuprate high-temperature superconductors.It accounts for the various intertwined spin and charge orders,and the superconductivity in the phase diagrams.To see the correlation effect on the intertwined orders,we implement the density matrix renormalization group method to simulate the t–J model in a small J case with t/J=10,which is in a deeper Mott region than that with t/J?3 in cuprate superconducting compounds.We examine the results on a six-leg lattice with both the nearest and next-nearest-neighbor hoppings and antiferromagnetic coupling,and find the absence of superconductivity and enhanced intertwined spin and charge orders in the phase diagram.Besides the stripe phases,we find a new SDW+CDW phase in which the spin modulation is a(π,π)antiferromagnetism,while the wavelength of the charge modulation is shorter than that of the stripe phases.Our results suggest the enhanced intertwined orders and suppressed superconductivity in the deep Mott region.

Emergent symmetry in quantum phase transition:From deconfined quantum critical point to gapless quantum spin liquid

The emergence of exotic quantum phenomena in frustrated magnets is rapidly driving the development of quantum many-body physics,raising fundamental questions on the nature of quantum phase transitions.Here we unveil the behaviour of emergent symmetry involving two extraordinarily representative phenomena,i.e.,the deconfined quantum critical point(DQCP)and the quantum spin liquid(QSL)state.Via large-scale tensor network simulations,we study a spatially anisotropic spin-1/2 square-lattice frustrated antiferromagnetic(AFM)model,namely the J1x-J1y-J2 model,which contains anisotropic nearestneighbor couplings J1x,J1y and the next nearest neighbor coupling J2.For small J1y/J1x,by tuning J2,a direct continuous transition between the AFM and valence bond solid phase is observed.With growing J1y/J1x,a gapless QSL phase gradually emerges between the AFM and VBS phases.We observe an emergent O(4)symmetry along the AFM–VBS transition line,which is consistent with the prediction of DQCP theory.Most surprisingly,we find that such an emergent O(4)symmetry holds for the whole QSL–VBS transition line as well.These findings reveal the intrinsic relationship between the QSL and DQCP from categorical symmetry point of view,and strongly constrain the quantum field theory description of the QSL phase.The phase diagram and critical exponents presented in this paper are of direct relevance to future experiments on frustrated magnets and cold atom systems.

High-performance non-Fermi-liquid metallic thermoelectric materials

Searching for high-performance thermoelectric(TE)materials in the paradigm of narrow-bandgap semiconductors is hampered by a bottleneck.Here we report on the discovery of metallic compounds,TiFe_(x)Cu_(2x−1)Sb and TiFe1.33Sb,showing the thermopower exceeding many TE semiconductors and the dimensionless figure of merits zTs comparable with the state-of-the-art TE materials.A quasi-linear temperature(T)dependent electrical resistivity in 2–700 K and the logarithmic T-dependent electronic specific heat at low temperature coexist with the high thermopower,highlighting the strong intercoupling of the non-Fermi-liquid(NFL)quantum critical behavior of electrons with TE transports.Electronic structure analysis reveals a competition between the antiferromagnetic(AFM)ordering and Kondo-like spin compensation as well as a parallel two-channel Kondo effect.The T-dependent magnetic susceptibility agrees with the quantum critical scenario of strong local correlation.Our work demonstrates the correlation among high TE performance,NFL quantum criticality,and magnetic fluctuation,which opens up directions for future research.

Floquet-engineered quantum state transfer in spin chains

Quantum state transfer between two distant parties is at the heart of quantum computation and quantum communication.Among the various protocols,the counterdiabatic driving(CD)method,by suppressing the unwanted transitions with an auxiliary Hamiltonian Hcd(t),offers a fast and robust strategy to transfer quantum states.However,Hcd(t)term often takes a complicated form in higherdimensional systems and is difficult to realize in experiment.Recently,the Floquet-engineered method was proposed to emulate the dynamics induced by Hcd(t)without the need for complex interactions in multi-qubit systems,which can accelerate the adiabatic process through the fast-oscillating control in the original Hamiltonian H0(t).Here,we apply this method in the Heisenberg spin chains,with only control of the two marginal couplings,to achieve the fast,high-fidelity,and robust quantum state transfer.Then we report an experimental implementation of our scheme using a nuclear magnetic resonance simulator.The experimental results demonstrate the feasibility of this method in complex many-body system and thus provide a new alternative to realize the high-fidelity quantum state manipulation in practice.

ZrTe_(5)中的面内垂直电流方向的负磁阻现象

拓扑材料独特的能带结构有时会导致一些不同寻常的磁输运现象,其中包括当外磁场施加在平行电流方向上时产生的面内纵向负磁阻效应.这种负磁阻效应被普遍认为是拓扑材料中存在手征反常的一个标志.本文报道了一种当面内磁场分别平行和垂直电流方向时,在拓扑材料ZrTe_(5)中观察到的面内负磁阻现象.该现象揭示了一种超出手征反常范畴的不同寻常的量子输运行为.研究人员构建了一种同时考虑贝里曲率和轨道磁矩的普适模型,用以定量解释他们观察到的实验现象.本文的研究结果为探索拓扑材料中的面内负磁阻现象提供了一种新的见解和思路.