Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session Q58: Frustration on Square LatticesFocus
|
Hide Abstracts |
Sponsoring Units: GMAG Chair: Jeff Rau, University of Windsor Room: Room 302 |
Wednesday, March 8, 2023 3:00PM - 3:36PM |
Q58.00001: Thermal properties of frustrated quantum magnets Invited Speaker: Frederic Mila The thermal properties of frustrated quantum magnets are a real challenge because, when formulated in the natural configuration basis, Quantum Monte Carlo simulations suffer from a very serious minus sign problem that excludes simulations below temperatures of the order of the coupling constants. In this talk, I will review recent numerical progress made on two fronts: (i) Quantum Monte Carlo simulations in the dimer basis. In this basis, there is no minus sign problem for fully frustrated models, and simulations can be performed down to arbitrarily low temperature. With these simulations, we have identified the presence of a thermal critical point terminating a line of first-order transitions in the fully frustrated bilayer model. (ii) Tensor network simulations. Using ancilla spins and a partial trace, the thermal ensemble can be accurately obtained by imaginary time evolution of a purified state, leading to reliable results down to temperatures only a few percents of the coupling constants regardless of the level of frustration. Using this approach, we have been able to show that the peak of the specific heat around 2 GPa and 4 K in SrCu2(BO3)2 is a thermal critical point akin to that of the fully frustrated bilayer, and to numerically verify the long-standing prediction that the spin-1/2 J1-J2 model on the square lattice has a thermal Ising transition for large enough J2/J1. |
Wednesday, March 8, 2023 3:36PM - 3:48PM |
Q58.00002: Pseudo-Goldstone modes and dynamical gap generation from order-by-thermal-disorder Subhankar Khatua, Michel J P Gingras, Jeffrey G Rau Accidental ground state degeneracies -- those not a consequence of symmetry -- are inevitably lifted by fluctuations, a phenomenon known as ``order-by-disorder’’ (ObD). In two dimensions at non-zero temperature, this presents a puzzle: while ObD suggests that thermal fluctuations will stabilize long-range order, for continuous degeneracies, divergence of long-wavelength fluctuations is expected to destroy it in accordance with the Mermin-Wagner-Hohenberg theorem. The resolution of this paradox is tied to the fate of the expected Goldstone modes and how a pseudo-Goldstone gap is dynamically generated by thermal fluctuations that drive the ObD. We study the properties and consequences of such pseudo-Goldstone modes in a minimal two-dimensional model: the ferromagnetic Heisenberg-compass model on a square lattice. Using spin-dynamics simulations and self-consistent mean-field calculations, we determine the pseudo-Goldstone gap and show that it scales with temperature T as T1/2, and that it is well-defined, with a thermally induced linewidth scaling as T3/2. We show explicitly how this pseudo-Goldstone mode eliminates the infrared-divergent fluctuations, ensuring true long-range order at T>0 in the thermodynamic limit. Finally, we show that all key features of this physics can be captured in a simple model of a particle moving in an effective potential generated by the fluctuation-induced free energy. |
Wednesday, March 8, 2023 3:48PM - 4:00PM |
Q58.00003: Study of phase transitions near SU(3) points in spin-1 systems using the Tensor Renormalisation Group Francisco Zuniga Frias, Chris Hooley Quantum spin-1 systems allow for non-geometric frustration between bilinear and biquadratic interactions. For these systems frustration leads to a rich phase diagram hosting exotic spin nematic phases with highly entangled ground states near SU(3)-symmetric points. We use Tensor Renormalisation Group methods (e.g. graph—independent local truncation TRG) to study the phase diagram of the spin-1 bilinear biquadratic Heisenberg model with focus on the phase transitions near SU(3)-symmetric points. TRG methods are useful to study both non-critical and critical phases and give insight to new mechanisms of spin-nematic phases and exotic ground states. |
Wednesday, March 8, 2023 4:00PM - 4:12PM |
Q58.00004: Where Is The Quantum Spin Nematic? Alexander L Chernyshev, Judit Romhanyi, Steven R White, Michael Zhitomirsky, Shengtao Jiang Our work offers the most definitive and unbiased study to date of the phase diagram of the paradigmatic model that has been recently proposed to host the quantum spin-nematic state, an elusive quantum analogue of a liquid crystal. Despite numerous theoretical and experimental efforts, the existence of the spin nematic state remains controversial. In our work, we employed a combination of rigorous analytical and unbiased density-matrix renormalization group approaches, which unambiguously established the extent of the spin nematic phase in a paradigmatic J1-J2 ferro-antiferromagnetic model on the square lattice, provided detailed insights into the microscopic nature of this phase, and elucidated general criteria for its stability that should be applicable to all other potential realizations of such phases. Our work also provides vital guidance to the intense experimental searches of the quantum spin nematics, arming them with realistic expectations. Our study advances understanding of the generic guiding principles in the search for the quantum spin nematics, emphasizing the importance of the restrictive many-body effects in the suppression of the analog of the superfluid stiffness in them, which are systematically neglected in the prior theoretical works. We also provide deep connections to the broader physics context, such as the symmetry of the bound states and their Bose-Einstein condensation. Our conclusions and phase diagram should be common to other models. |
Wednesday, March 8, 2023 4:12PM - 4:24PM |
Q58.00005: Unusual magnetic order and crystalline electric fields in itinerant Cerium-based materials Mitchell Bordelon, Clement Girod, Joe D Thompson, Filip Ronning, Clarina dela Cruz, Stuart Calder, Riku Yamamoto, Michihiro Hirata, Sean Thomas, Eric D Bauer, Priscila Rosa Magnetic frustration can generate new quantum phases of matter with exotic physical properties. Lanthanide-based materials can generate frustration from the geometrical arrangement of magnetic ions, magnetocrystalline anisotropy from spin-orbit coupling (SOC) and crystalline electric field (CEF) effects, Kondo interactions, and conduction electron mediated Ruderman-Kittel-Kasuya-Yosida (RKKY) magnetic exchange interactions. Here, we report investigations of two Ce-based materials, CeLiBi2 and CeLi3Bi2, with frustrated magnetic ground states. In tetragonal CeLiBi2, a complex competition between CEF anisotropy and extended magnetic exchange leads to a multitude of intertwined quantum phases. This includes hard-axis metamagnetism, highly mobile carriers, incommensurate cycloidal magnetic order below 3.4 K in neutron diffraction data, and quantum oscillations in dilatometry and resistivity measurements. Neutron diffraction and NMR measurements reveal itinerant triangular lattice CeLi3Bi2 exhibits stripy antiferromagnetic order below 1.2 K with small Ce moment magnitudes. In CeLi3Bi2, we further investigate the splitting of the local Ce ion D3d CEF utilizing combined magnetic susceptibility, specific heat, and magnetospectroscopy measurements. |
Wednesday, March 8, 2023 4:24PM - 4:36PM |
Q58.00006: Evolution of low-dimensional magnetism in Mg-substituted CoTa2O6 Thomas W Heitmann, Raju Baral, Harikrishnan S Nair Co2+ moments in the trirutile compound CoTa2O6 form a square-net in two-dimensions. The system exhibits three-dimensional ordering described by a propagation vector of (1/4,1/4,0) below a Neel temperature of TN=6.2 K wherein moments align (++--) in chains along the (110) and (1-10). Anomalies in the magnetization and specific heat have indicated the presence of correlations above the Neel temperature, whereas no diffuse scattering was observed the elastic neutron scattering signal as would be expected for three-dimensional short-range order. Further, it has been shown that the ordering at 6.4 K is destroyed by even a small amount (x = 0.1) of non-magnetic doping with Mg on the Co site. We therefore have investigated the series Co1-xMgxTa2O6 via inelastic neutron scattering in order to gain insight into the spin correlations both below and above the ordering temperature and their evolution with lattice dilution. We discuss the results in the context of anisotropic exchange interactions and reduced dimensionality of the magnetic lattice. |
Wednesday, March 8, 2023 4:36PM - 4:48PM Author not Attending |
Q58.00007: Lattice and antiferromagnetic symmetries in disorder-free spinel oxide ZnFe2O4. Margarita Dronova, Yejun Feng, Feng Ye, Zachary Morgan, Daniel I Khomskii, Vaclav Petricek, Daniel M Silevitch Pyrochlore-structured spinel magnets are of broad theoretical and experimental interest because of their potential to host frustrated spin configurations. However, many 3d spinel oxides are plagued by a high level of disorder, expressed as both off-stoichiometry and site mixing. As magnetism is highly sensitive to those disorders, the antiferromagnetic structure of ZnFe2O4 has not been fully resolved; two neutron powder diffraction refinements in the 1970s failed to provide a consistent model of the spin arrangement. A large amount of short-range magnetic diffuse scattering has had an adverse effect on the refinement of this presumed anitferromagnet. In addition, the spin structure with a wavevector k= (1/2, 1, 0) was assumed to be non-collinear, which brings an intrinsic difficulty of refinement solely using powder diffraction. Recently, we resolved both the site disorder and stoichiometric issues in this spinel magnet and took neutron magnetic diffraction data on a piece of clean-limit single crystal at CORELLI [1]. Our lattice diffraction study has revealed that the symmetry group is no longer the central-symmetric type of Fd-3m, but instead is of space group F-43m with a broken inversion symmetry. All these have allowed a refreshed perspective of the spin structure in ZnFe2O4. We also discuss how the spin structure helps to understand the magnetic behavior in the H-T magnetic phase diagram. |
Wednesday, March 8, 2023 4:48PM - 5:00PM |
Q58.00008: Uncovering the orbital order in MgV2O4 Harry Lane, Paul M Sarte, Guratinder Kaur, Angel Arevalo-Lopez, Robin Perry, Bertrand Roessli, Yixi Su, Russell Ewings, Stephen D Wilson, Peter Böni, Paul Attfield, Chris Stock In spinel oxides, AB2O4, the B sites form geometrically frustrated pyrochlore lattices. This suppresses TN and may give rise to exotic macroscopically degenerate classical spin liquid states [1]. Breaking of this degeneracy is typically due to longer-range couplings or lattice distortions. |
Wednesday, March 8, 2023 5:00PM - 5:12PM |
Q58.00009: High Pressure Magnetometry and Neutron Scattering of the Frustrated Spinel MgCr2O4 Lila S Nassar, Harry Lane, Xiaojian Bai, Ovidiu O Garlea, Seyed M Koohpayeh, Martin P Mourigal Magnesium Chromate (MgCr2O4) is an example of a cubic AB2O4 spinel in which the magnetic Cr3+ ion occupies a pyrochlore lattice that hosts highly frustrated antiferromagnetic spin interactions. Its proximity to two distinct highly degenerate phases, the coulomb and spin-spiral-liquid, results in unique behavior prior to the onset of magnetic ordering at around 12K. Compression of the material under high-pressure may permit the tuning of exchange interaction terms, possibly enabling one of these nearly degenerate states to dominate. |
Wednesday, March 8, 2023 5:12PM - 5:24PM |
Q58.00010: Vison crystal formation in quantum spin ice on the breathing pyrochlore lattice Alaric L Sanders, Claudio Castelnovo The U(1) spin liquid phase of pyrochlore quantum spin ice has long fascinated theorists with its deep connections to compact lattice QED. Recent excitement has come from the experimental discovery of pseudospin-12 breathing pyrochlores, including certain chromium spinels and Ba3Yb2Zn5O11, in which the ‘up’ and ‘down’ tetrahedra are different physical sizes. We show here that the often-neglected Jz± coupling between spin-1/2 pyrochlore pseudospins, in combination with a breathing lattice, can produce a staggered offset in the ground state’s plaquette fluxes. Very strong breathing anisotropies realise an unconventional ‘U(1)π/2 phase,’ which in some sense interpolates between the known U(1)0 and U(1)π phases of standard quantum spin ice models. |
Wednesday, March 8, 2023 5:24PM - 5:36PM |
Q58.00011: Magnetic phase competition in the highly frustrated iridate K2IrCl6 Qiaochu Wang, Wei Tian, Andrey Podlesnyak, Philip J Ryan, Jong-Woo Kim, Kemp Plumb Frustrated magnetic materials have been studied to a great extent for their possibilities of realizing novel magnetic states such as spin ice or spin liquids [1]. K2IrCl6 is an exciting compound in a model antiferromagnet with face-centered-cubic frustration. Its extensive degeneracy could be lifted by various mechanisms including quantum or thermal fluctuations, further neighbor interaction, exchange anisotropies, and magneto-structural coupling, making it a model system to study the ground-state selection and explore the magnetic phase diagram on the fcc lattice. In this talk, I will discuss recent elastic and inelastic neutron scattering results on K2IrCl6 that indicate the coexistence of a minority type-I phase with k=(100) and a previously revealed type-III phase with k=(1 ½ 0). Given that the type-III magnetic order is the dominant phase, the type-I magnetic order could be stabilized through local deviations from cubic symmetry, quantum order-by-disorder effect, or both [2,3]. This study will help us understand the ground-state selections by various mechanisms so that we could possibly suppress the magnetic order and stabilize the quantum spin liquid state in frustrated magnets. |
Wednesday, March 8, 2023 5:36PM - 5:48PM |
Q58.00012: Quadrupole and octupole excitations in the magnetoelectric akermanites Judit Romhanyi, Karlo Penc We study the magnetoelectric multiferroic compounds, A2CoGe2O7 (A=Ba, Sr), in which the coexistence of ferroelectric and magnetic order enables a strong cross-coupling and the mutual control of magnetization by electric and polarization by magnetic fields. The magnetoelectric response is not limited to the static properties but is revealed in spin excitations too, characterized by mixed magnetic and electric dipole components. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700