Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session M46: Quasi-2D Frustration: Honeycomb Lattice and Other Geometries |
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Sponsoring Units: GMAG Chair: Kate Ross, Colorado State University Room: 708 |
Wednesday, March 4, 2020 11:15AM - 11:27AM |
M46.00001: Topological Quantum Many-Body Scars in Quantum Dimer Models Alexander Seidel, Julia Wildeboer, Anne E. B. Nielsen, Onur Erten We construct two-dimensional lattice models with quantum dimer degrees of freedom that violate the eigenstate thermalization hypothesis (ETH) by featuring quantum many-body scars in their excitation spectrum. These scars consist of single exactly known excited eigenstates with atypical (area law) entanglement entropy. We explicitly construct such models for the kagome and checkerboard lattices. We compute entanglement entropy numerically for the surrounding states, and analytically for the scar states themselves. Furthermore, we corroborate the non-integrable nature of these quantum dimer models by studying the statistics of the spacings between consecutive energy levels. |
Wednesday, March 4, 2020 11:27AM - 11:39AM |
M46.00002: Novel Quantum Phase Transition of the Shastry-Sutherland Model Toru Sakai, Hiroki Nakano The Shastry-Sutherland model - the S = 1/2 Heisenberg antiferromagnet on the square lattice accompanied by orthogonal dimerized interactions - is studied by the numerical-diagonalization method. Large-scale calculations provide results for larger clusters that have not been reported yet. The present study successfully captures the phase boundary between the dimer and plaquette-singlet phases and clarifies that the spin gap increases once when the interaction forming the square lattice is increased from the boundary. Our calculations strongly suggest that in addition to the edge of the dimer phase given by J2/J1∼0.675 and the edge of the Neel-ordered phase given by J2/J1∼0.76, there exists a third boundary ratio J2/J1∼0.70 that divides the intermediate region into two parts, where J1 and J2 denote dimer and square-lattice interactions, respectively. We report the result from the investigation about this possible novel quantum phase transition in the plaquette singlet phase[1]. |
Wednesday, March 4, 2020 11:39AM - 11:51AM |
M46.00003: Antiferromagnetic-to-ferrimagnetic phase transition in frustrated polar magnet CaBaCo4O7 Tsuyoshi Omi, Yoshito Watanabe, Nobuyuki Abe, Yusuke Tokunaga, Akiko Nakao, Koji Munakata, Hajime Sagayama, Taka-hisa Arima Magnetic frustration often plays important roles in multiferroic properties as is exemplified by the electric polarization induced by the spiral magnetic order. CaBaCo4O7 belongs to the orthorhombic space group Pbn21. Magnetic Co ions form Kagomé- and triangular- lattice layers, which alternately stack along the c-axis. CaBaCo4O7 shows a ferrimagnetic transition at Tc ∼ 60 K at zero magnetic field. CaBaCo4O7 is a multiferroic material hosting magnetic frustration[1]. It exhibits an electric polarization change of about 17 mC/m2 at the ferrimagnetic transition which is the largest among all the multiferroic materials so far[2]. The specific heat and the electric permittivity of single crystal CaBaCo4O7 exhibits another anomaly at TN∼69 K slightly higher than Tc in zero magnetic field, while the origin of the anomaly was not clarified[2]. |
Wednesday, March 4, 2020 11:51AM - 12:03PM |
M46.00004: Sign-switching of dimer correlations in SrCu2(BO3)2 under hydrostatic pressure Simon Bettler, Lena Stoppel, Zewu Yan, Severian Gvasaliya, Andrey Zheludev Magnetic and vibrational excitations in SrCu2(BO3)2 are studied using Raman spectroscopy at hydrostatic pressures up to 34 kbar and temperatures down to 2.6 K. The frequency of a particular optical phonon, the so-called pantograph mode, shows a very strong anomalous temperature dependence below about 40 K. We link the magnitude of the effect to the magnetic exchange energy on the dimer bonds in the Sutherland-Shastry spin lattice in this material. The corresponding dimer spin correlations are quantitatively estimated and found to be strongly pressure dependent. At around P2~22 kbar they switch from antiferromagnetic to being predominantly ferromagnetic. |
Wednesday, March 4, 2020 12:03PM - 12:15PM |
M46.00005: Large spin fluctuation in the magnetization process of S=1/2 frustrated square lattice model Tsuyoshi Okubo In the frustrated spin systems, a lot of interesting phenomena including non-collinear magnetic orders, magnetization plateaus and spin liquids occur. Such frustrated interactions often appear in geometrically frustrated lattices, such as triangular, kagome or pyrochlore lattices. In addition to these lattice, when we consider further neighbor interactions or combination of ferromagnetic and antiferromagnetic interactions, frustrations can happen even in the square lattice. |
Wednesday, March 4, 2020 12:15PM - 12:27PM |
M46.00006: Quantum Phases Diagram of the Plaquette State of the Shastry-Sutherland Compound SrCu2(BO3)2 Sara Haravifard, Zhenzhong Shi, Sachith Dissanayake, David E Graf, Philippe R. Corboz, Frederic Mila, Daniel Silevitch, Thomas F Rosenbaum, Hanna Dabkowska, Casey Marjerrison The Shastry-Sutherland compound SrCu2(BO3)2 features 2D layers of Cu2+ S=1/2 spin dimers which are orthogonal to each other. The ground state of the system is determined by the relative strength of the nearest neighbor and next-nearest neighbor interactions, J and J’ respectively. The ratio of J/J’ can be tuned continuously by application of hydrostatic pressure. The ground state changes from a spin dimer singlet state at ambient pressure to an antiferromagnet state at high pressure. At intermediate pressure a novel 4-spin plaquette singlet state has recently been reported. However, the nature of this plaquette state and how it evolves into other phases remains unclear. Here, we report a comprehensive study of the quantum phase diagram of the plaquette state by tuning temperature, pressure, magnetic field, and chemical doping. We mapped out the evolution of the ground states using complementary techniques such as magnetic susceptibility, magnetization and neutron scattering measurements. The results provide insights into the nature of the plaquette state, and also has implications in areas such as studies of deconfined quantum criticality. |
Wednesday, March 4, 2020 12:27PM - 12:39PM |
M46.00007: Critical properties of a fractionally frustrated XY model on the square lattice Tasrief Surungan, Zohar Nussinov
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Wednesday, March 4, 2020 12:39PM - 12:51PM |
M46.00008: Exact Solution and Correlations of a Quantum Dimer Model on the Checkerboard Lattice Julia Wildeboer, Zohar Nussinov, Alexander Seidel For decades, constrained models with dimer degrees of freedom have been a powerhouse of statistical physics and various branches of theoretical and mathematical physics, in particular aspects of quantum magnetism. For analytic purposes, their utility is usually limited to models defined on planar lattice graphs, where, thanks to a powerful theorem by Kasteleyn, many questions can be answered exactly. Here we present analytic results on a special dimer model on a {\it nonplanar} checkerboard lattice of interacting dimers, which does not permit for parallel dimers to surround diagonal links. We report exact results on the enumeration of closed packed dimer coverings on finite checkerboard lattices under periodic boundary conditions. Furthermore, we comment on the behavior of the dimer-dimer correlations and find that the correlations between any two dimers vanish identically if their distance is larger than two unit cells. Connections with $\mathbb{Z}_{2}$ gauge theory, known from planar models, are extended to the present case. |
Wednesday, March 4, 2020 12:51PM - 1:03PM |
M46.00009: Magnetic structure of the stuffed honeycomb antiferromagnet GdInO3 Erxi Feng, Xianghan Xu, Eve Emmanouilidou, Jae Wook Kim, Yan Wu, LEI DING, Alexander Kolesnikov, Ni Ni, Sang-Wook Cheong, Huibo Cao Rare-earth indium oxides RInO3 (R = rare earth), in which R3+ ions occupy two nonequivalent sites forming a honeycomb lattice with a superimposed triangular lattice (so-called stuffed honeycomb lattice), present an excellent platform to study the combination of two different frustrated lattices. Since the total angular moment L of Gd3+ ion is zero, GdInO3 is expected as pure spin magnetism and may be considered as a classical Heisenberg spin system in the stuffed honeycomb lattice. A high quality isotope single crystal 160GdInO3 was synthesized for neutron scattering studies to avoid the high neutron absorption of natural Gd. The specific heat measurement shows that the compound exhibits two step magnetic phase transitions at 2.2 K and 1.08 K corresponding to two different antiferromagnetic phases that were characterized by single crystal neutron diffraction. These phases transition may be explained via the order-by-disorder mechanism. |
Wednesday, March 4, 2020 1:03PM - 1:15PM |
M46.00010: Frustrated magnetic interactions in an S=3/2 bilayer honeycomb lattice compound Bi3Mn4O12(NO3) Masaaki Matsuda, Sachith Dissanayake, Douglas L Abernathy, Yiming Qiu, John Copley, Nobuhiro Kumada, Masaki Azuma Inelastic neutron scattering study has been performed in an S=3/2 bilayer honeycomb lattice compound Bi3Mn4O12(NO3) at ambient and high magnetic fields [1]. Relatively broad and monotonically dispersive magnetic excitations were observed at ambient field, where no long range magnetic order exists. In the magnetic field-induced long-range ordered state at 10 T, the magnetic dispersions become slightly more intense, albeit still broad as in the disordered state, and two excitation gaps, probably originating from an easy-plane magnetic anisotropy and intrabilayer interactions, develop. Analyzing the magnetic dispersions using the linear spin-wave theory, we estimated the intraplane and intrabilayer magnetic interactions, which are almost consistent with those determined by ab initio density functional theory calculations [2], except the third and fourth neighbor intrabilayer interactions. Most importantly, as predicted by the theory, there is no significant frustration in the honeycomb plane but frustrating intrabilayer interactions probably give rise to the disordered ground state. |
Wednesday, March 4, 2020 1:15PM - 1:27PM |
M46.00011: Observations of antiferromagnetic, antiferroelectric and ferroelastic orderings in honeycomb-lattice Mn2V2O7 Hung-Cheng Wu, Dong-Jie Hsieh, Tsung-Wen Yen, Po-Jung Sun, D. Chandrasekhar Kakarla, Jim-Long Her, Y. H. Matsuda, Chung-Kai Chang, Yu-Chun Chuang, Yen-Chung Lai, Melissa Gooch, Liangzi Deng, Kyle Grant Webber, Ching (Paul) W Chu The dielectric and magnetic anomalies were observed in Mn2V2O7 between 275 K and 300 K. Isothermal capacitance-stress hysteresis loop measurements along with crystallographic Aizu notation supported a martensitic phase transition (TM) driven ferroelastic behavior near room temperature. Another dielectric anomaly was also observed near the long-range antiferromagnetic (AFM) ordering temperature (TN ~ 16.4 K) along with noticeable magnetodielectric (MD) coupling below TN, signifying the multiferroic nature of Mn2V2O7. With increasing pressure, the antiferromagnetic ordering (TN) greatly increased, while the (TM) was suppressed. Taking all of these comprehensive research findings into account, we suggest that Mn2V2O7 is a unique multifunctional material with the coexistence of antiferromagnetic, antiferroelectric and ferroelastic orderings. |
Wednesday, March 4, 2020 1:27PM - 1:39PM |
M46.00012: NMR study on the honeycomb-lattice antiferromagnet Na2Co2TeO6 Weiqiang Yu, Ze Hu, Yuan Li, Weiliang Yao The honeycomb-lattice magnetic materials have caused a lot of research interests recently, because of possible realization of Kitaev or proximate Kitaev quantum spin liquid in these systems. Na2Co2TeO6, as a new honeycomb-lattice antiferromagnet, has a zigzag magnetic order which can be suppressed by magnetic field. Here we report our NMR studies on Na2Co2TeO6 single crystals, and show rich properties revealed in this system both at zero field and at finite fields. |
Wednesday, March 4, 2020 1:39PM - 1:51PM |
M46.00013: Cooperative liquid-like paramagnetic state in nanoengineered honeycomb lattice George Yumnam, Yiyao Chen, Jiasen Guo, Haile Arena Ambaye, Valeria Lauter, Deepak K Singh Geometrically frustrated honeycomb structured artificial magnetic lattice has emerged as a testbed to explore the competing physics of energy vs. entropy in a thermally tuned magnetic phase transition. A magnetic honeycomb lattice with competing exchange interactions between Ising moments is theoretically predicted to exhibit disordered magnetic state with macroscopic degeneracy. We demonstrate the realization of a liquid-like magnetic state, comprised of low integer and energetically forbidden high integer magnetic charges, in nanostructured magnetic honeycomb lattice of ultra-small, sub-12 nm, connecting elements. Magnetic charges, related to magnetic moment and interacting via magnetic Coulomb's interaction, act as quantum mechanical entities. Detailed polarized neutron reflectometry measurements on magnetic honeycomb reveal a robust degenerate ground state at low temperature, which remains minimally affected by magnetic field application. Our finding provides a new vista to investigate quantum mechanical phenomena from the perspective of dynamic magnetic charges, instead of magnetic moments, in a classical system. |
Wednesday, March 4, 2020 1:51PM - 2:03PM |
M46.00014: Field induced phase transition in the classical honeycomb Gamma model Zhongzheng Tian, Zhijie Fan, Preetha Saha, Gia-Wei Chern Recent studies have indicated the importance of the symmetric aniostropic exchange interaction, also called the Γ term, in the so-called Kitaev materials. Moreover, a new type of classical spin liquid was shown to be the ground state of the classical Γ model on the honeycomb lattice [1]. In our previous paper [2], we further demonstrated that thermal order-by-disorder drives the system toward a novel plaquette ordering that spontaneously breaks the lattice translation symmetry. In this work, we study the effects of magnetic field on the plaquette-ordered state. Our extensive Monte Carlo simulations uncover a field-induced phase transition above which the √3×√3 flux order is replaced by a new spin order. We will present our characterization of this intermediate phase and discuss the nature of the phase transitions. [1] I. Rousochatzakis and N. B. Perkins, Phys. Rev. Lett. 118, 147204 (2017). [2] P. Saha, Z. Fan, D. Zhang, and G.-W. Chern, Phys. Rev. Lett. 122, 257204 (2019). |
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