Article
Materials Science, Multidisciplinary
A. V. Syromyatnikov
Summary: In this study, a spin-1/2 Heisenberg antiferromagnet on the triangular lattice was discussed using the bond-operator technique (BOT). It was found that high-energy collective excitations and another high-energy quasiparticle exist in the system. Quantum fluctuations considerably alter the properties of conventional magnons, and the anomalous spin dynamics observed experimentally recently cannot be described by SWT.
Article
Materials Science, Multidisciplinary
Yuan Gao, Yu-Chen Fan, Han Li, Fan Yang, Xu-Tao Zeng, Xian-Lei Sheng, Ruidan Zhong, Yang Qi, Yuan Wan, Wei Li
Summary: The recently synthesized NBCP compound is found to be an ideal realization of a S = 1/2 triangular-lattice antiferromagnet with significant easy-axis spin exchange anisotropy. By combining automatic parameter searching and tensor-network simulations, a microscopic model is established to accurately describe the material's properties, fitting well with experimental data.
NPJ QUANTUM MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Tomonari Mizoguchi, Yoshihito Kuno, Yasuhiro Hatsugai
Summary: The study reveals characteristic band structures of fermions on a square kagome lattice, including flat bands and two spin-1 Dirac cones. Additionally, in the presence of an external field, the profile of the Chern numbers around the modified spin-1 Dirac cones coincides with the conventional one.
Article
Materials Science, Multidisciplinary
Rajiv R. P. Singh
Summary: We discuss the thermodynamic and magnetic properties of a competing high-spin/low-spin two-orbital two-electron model on a square lattice that may be relevant to nickelates like Ba2NiO2(AgSe)2. We focus on parameter regimes where a high-spin (S = 1) and a low-spin (S = 0) state are energetically close and discuss various exchange processes in such a system. The model we study is different from the recently proposed Kondo-necklace model, although there are similarities in terms of ground-state phases and symmetries. The properties of different phases and phase transitions can be easily distinguished experimentally.
Article
Materials Science, Multidisciplinary
Zhen Zhao, Claudio Verdozzi, Ferdi Aryasetiawan
Summary: The self-consistent Green's function method is used to study the ground state spin patterns and magnetic structure factors of two-dimensional magnetic systems with frustrated spin-1/2 Heisenberg exchange coupling. The method shows improved accuracy compared to random phase approximation treatments in the case of scalar product interactions, while higher corrections are needed for cross-product interactions. The results indicate the potential advantages of this method in describing systems with a large number of atoms and long-range interactions.
Article
Materials Science, Multidisciplinary
P. S. Savchenkov, A. F. Barabanov
Summary: In this study, we investigate the spin excitations in an ordered square quantum antiferromagnet under a magnetic field, predicting the emergence of three modes and a hybridization effect due to the field. The theoretical predictions are compared with exact diagonalization and neutron scattering experiments to confirm the validity of the model.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2021)
Article
Physics, Multidisciplinary
Xin-Yang Liu, Yuan Gao, Han Li, Wentao Jin, Junsen Xiang, Hai Jin, Ziyu Chen, Wei Li, Gang Su
Summary: Quantum spin liquids have no magnetic order and can be cooled using magnetocaloric effects, making them promising for helium-free refrigeration in space applications and quantum technologies.
COMMUNICATIONS PHYSICS
(2022)
Article
Materials Science, Multidisciplinary
Yuya Haraguchi, Akira Matsuo, Koichi Kindo, Zenji Hiroi
Summary: In this study, the hydrothermal synthesis of bluebellite Cu6IO3(OH)10Cl as a potential candidate for spin-1/2 maple-leaf lattice antiferromagnets was reported. Measurements revealed a magnetic transition at 17K, indicating a one-dimensional spin correlation in the apparently two-dimensional lattice.
Article
Materials Science, Multidisciplinary
Mutsuki Saito, Ryunosuke Takagishi, Nobuyuki Kurita, Masari Watanabe, Hidekazu Tanaka, Ryuji Nomura, Yoshiyuki Fukumoto, Kazuhiko Ikeuchi, Ryoichi Kajimoto
Summary: Cs2Cu3SnF12 and Rb2Cu3SnF12 are two spin-1/2 antiferromagnets with different structures, and their magnetic excitation structures were investigated using inelastic neutron scattering. Four single-magnon excitation modes were observed in Cs2Cu3SnF12, and a broad excitation continuum was found. In Rb2Cu3SnF12, singlet-triplet excitations from the pinwheel VBS state were confirmed, along with ghost modes caused by the enlargement of the chemical unit cell.
Article
Physics, Multidisciplinary
Tessa Cookmeyer, Johannes Motruk, Joel E. Moore
Summary: This study shows that under certain physical parameters, the additional four-spin interactions naturally generated in the Hubbard model will stabilize a chiral spin liquid of Kalmeyer-Laughlin type. By rewriting the interactions mean-field, a physical understanding of the origin of this spin liquid can be obtained.
PHYSICAL REVIEW LETTERS
(2021)
Article
Materials Science, Multidisciplinary
Johannes Richter, Oleg Derzhko, Juergen Schnack
Summary: Over the last decade, the interest in the spin-1/2 Heisenberg antiferromagnet (HAF) on the square kagome lattice has been growing. This model system is a prominent example of quantum magnetism with a quantum paramagnetic ground state, flat-band physics near the saturation field, and quantum scars. Recent numerical investigations have revealed a gapless spin liquid in the square kagome magnet. The study also provides insights into specific heat, entropy, and susceptibility, revealing low-temperature shoulder below the major maximum and a change in curvature just at a specific temperature, attributed to low-lying singlet excitations and the singlet-triplet gap.
Article
Materials Science, Multidisciplinary
Ellen Fogh, Otto Mustonen, Peter Babkevich, Vamshi M. Katukuri, Helen C. Walker, Lucile Mangin-Thro, Maarit Karppinen, Simon Ward, Bruce Normand, Henrik M. Ronnow
Summary: We investigate the influence of randomness and magnetic frustration in the series of S = 1/2 Heisenberg square-lattice compounds Sr2CuTe1???xWxO6. By substituting W for Te, the magnetic interactions are dramatically altered from nearest-neighbor to next-nearest-neighbor antiferromagnetic coupling. Neutron scattering measurements are performed to study the magnetic ground state and excitations for different x values. A bond-disorder model is proposed to explain the ground states with short-ranged spin correlations in the mixed compounds. The calculated neutron diffraction patterns and powder spectra agree well with the experimental data.
Article
Materials Science, Multidisciplinary
Sebin J. Sebastian, S. S. Islam, A. Jain, S. M. Yusuf, M. Uhlarz, R. Nath
Summary: In this study, the structural and magnetic properties of the frustrated spin-5/2 triangle lattice antiferromagnet Na3Fe(PO4)2 were investigated using various experimental techniques. The results show the presence of magnetic long-range order at low temperatures and a field-induced spin-flop transition. The intermediate value of the frustration ratio reflects moderate frustration in the compound.
Article
Materials Science, Multidisciplinary
A. Syromyatnikov
Summary: We discuss the spin -21 J1-J2 model on the triangular lattice using bond-operator theory (BOT). We obtain four phases upon J2 increasing: the phase with 120 degrees ordering, the spin-liquid phase, the state with the collinear stripe order, and the spiral phase. The 120 degrees and the stripe phases are discussed in detail. All calculated static characteristics are in good agreement with previous numerical findings. We observe the evolution of the quasiparticles' spectra and dynamical structure factors (DSFs) in the 120 degrees phase. In the stripe phase, we observe the splitting of the magnon spectrum by quantum fluctuations, and the appearance of additional spin-1 and spin-0 quasiparticles that give anomalies in the DSFs. We also find a special spin-0 quasiparticle named the singlon that only produces a peak in the four-spin correlator and is invisible in the DSF.
Article
Multidisciplinary Sciences
Sahar Satoori, Saeed Mahdavifar, Javad Vahedi
Summary: The ground state phase diagram of the dimerized spin-1/2 XX honeycomb model in the presence of a transverse magnetic field is investigated using numerical exact techniques. The quantum correlations, concurrence, and quantum discord among nearest-neighbor spins are analyzed, demonstrating their ability to capture the position of quantum critical points and provide information on long-ranged critical correlations. Additionally, a magnetic-entanglement behavior starting from the saturation field is addressed.
SCIENTIFIC REPORTS
(2022)
Article
Multidisciplinary Sciences
L. Schwarz, B. Fauseweh, N. Tsuji, N. Cheng, N. Bittner, H. Krull, M. Berciu, G. S. Uhrig, A. P. Schnyder, S. Kaiser, D. Manske
NATURE COMMUNICATIONS
(2020)
Article
Physics, Multidisciplinary
Mi Jiang, Mona Berciu, George A. Sawatzky
PHYSICAL REVIEW LETTERS
(2020)
Article
Physics, Multidisciplinary
Krzysztof Bieniasz, Steven Johnston, Mona Berciu
Summary: Resonant inelastic X-ray scattering (RIXS) is increasingly used for characterizing low-energy collective excitations in materials and requires sophisticated theoretical descriptions, especially with improving instrument resolution. A versatile variational approximation has been proposed for calculating RIXS spectra in weakly doped materials, illustrating its potential in studying electron mobility and the shortcomings of the widely used local approximation. This work highlights the importance of accurate theoretical descriptions of electron-phonon coupling in interpreting RIXS data.
Article
Materials Science, Multidisciplinary
Yau-Chuen Yam, George A. Sawatzky, Mona Berciu
Summary: This study investigates the impact of hole-phonon coupling on the properties of quasiparticles, showing that even with strong coupling the increase in effective mass of the quasiparticle is minor. It reveals the reasons for this suppression in strongly correlated systems.
Article
Materials Science, Multidisciplinary
M. Berciu
Summary: We propose a simple variational solution for calculating one-particle spectral functions in lattice models of spinless metals with strong electron-phonon coupling. This method offers new insights into polaronic behavior in a largely unexplored part of the parameter space, far from the region where the Migdal theorem holds. The accuracy of the results needs to be verified against numerical calculations.
JOURNAL OF PHYSICS-MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Monodeep Chakraborty, Sankeerth S. Narayan, R. Vigneshwaran, Mona Berciu
Summary: Variational exact diagonalization is used to investigate the properties of single polarons in four different dual models, including short-range off-diagonal (Peierls) and longer-range diagonal (Holstein or breathingmode) couplings. The results show strong sensitivity to the range of the diagonal coupling and dependence on the specific form of the diagonal coupling, suggesting careful consideration is required when making quantitative comparisons with experimental data.
Article
Materials Science, Multidisciplinary
Leonard Ruocco, Mona Berciu, Jeff F. Young
Summary: Electromagnetically coupled two-level systems have been studied for their role in quantum information processing applications in condensed matter. In this study, the influence of phonon excitations on the electromagnetic response of these systems is investigated, including the effects of phonon-assisted transitions and lifetime broadening. The results reveal the impact of the phonon frequency distribution on the spectral weight of the zero-phonon transition and the phonon sidebands, as well as the broadening of the zero-phonon line due to nondiagonal electron-phonon coupling. This study emphasizes the importance of considering both forms of electron-phonon coupling in the analysis of these systems, and provides a formalism that can be extended to higher orders of coupling and realistic phonon spectral functions.
Article
Materials Science, Multidisciplinary
Krzysztof Bieniasz, Steve Johnston, Mona Berciu
Summary: The community currently lacks a complete understanding of how RIXS experiments probe the electron-phonon interaction in solids. In this study, we use a variational approximation method to calculate RIXS spectra in band insulators and investigate the influence of electron and phonon dispersion in the intermediate state of the scattering process. Our results show that even for momentum-independent electron-phonon coupling, the inclusion of electron and phonon dispersion and their interplay lead to significant momentum variations in RIXS intensity and nontrivial changes in the excitation line shapes. These findings highlight the challenges in interpreting RIXS data in real materials.
Article
Materials Science, Multidisciplinary
Alberto Nocera, John Sous, Adrian E. Feiguin, Mona Berciu
Summary: The study utilizes the density matrix renormalization group method to investigate a one-dimensional chain with Peierls electron-phonon coupling, showing stability against phase separation in the dilute density limit and indicating potential application of Peierls bipolaron liquids in high-Tc superconductivity.
Article
Materials Science, Multidisciplinary
Rodrigo Chavez Zavaleta, Stepan Fomichev, Giniyat Khaliullin, Mona Berciu
Summary: The study focuses on the effects of crystal field splitting, lattice distortions, and strain on the charge, magnetic, and orbital order in undoped two-dimensional nickelate monolayers. It is found that 2D confinement leads to a strong preference for the planar dx2-y2 orbital, even in the absence of crystal-field splitting. Additionally, the application of tensile strain enhances cupratelike phase and phases with orbital polarization in general.
Article
Materials Science, Multidisciplinary
Mi Jiang, George A. Sawatzky, Mona Berciu, Steven Johnston
Summary: In this study, classical Monte Carlo simulations were used to investigate a semiclassical three-orbital model with off-diagonal electron-phonon interactions, demonstrating the existence of (bi)polaron correlations at high temperatures and under hole doping conditions. By analyzing the relationship between various local quantities and lattice degrees of freedom, similarities were identified between heating- and doping-induced melting of a bond-disproportionated insulator at a microscopic level. The results suggest that (bi)polaron physics can serve as a unifying concept to understand the complex phase diagram of bismuth perovskites.
Article
Materials Science, Multidisciplinary
Fang Han Lim, Tomonori Ida, Mona Berciu
Summary: The study found that superconductivity with very high critical temperatures can occur at all carrier concentrations if the electron-phonon coupling is not too weak, with a gap of s + s* symmetry closing on the Fermi surface for appropriate parameters. Additionally, the possibility of finding p-type superconductivity was revealed, although it was found to be unstable within the approximations used in the study.
Article
Materials Science, Multidisciplinary
Yau-Chuen Yam, Mirko M. Moeller, George A. Sawatzky, Mona Berciu
Article
Materials Science, Multidisciplinary
Mi Jiang, Mirko Moeller, Mona Berciu, George A. Sawatzky
Article
Materials Science, Multidisciplinary
Stepan Fomichev, Giniyat Khaliullin, Mona Berciu