Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session A60: Charge Density WavesFocus Recordings Available
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Chair: Adam Wei Tsen, University of Waterloo Room: Hyatt Regency Hotel -DuSable C |
Monday, March 14, 2022 8:00AM - 8:36AM |
A60.00001: Charge density waves in 1T-TaS2 Invited Speaker: Adina A Luican-Mayer
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Monday, March 14, 2022 8:36AM - 8:48AM |
A60.00002: Strain-induced topological charge density wave in monolayer NbSe2 Wei-Chi Chiu, Sougata Mardanya, Robert S Markiewicz, Jouko Nieminen, Bahadur Singh, Tugrul Hakioglu, Amit Agarwal, Tay-Rong Chang, Hsin Lin, Arun Bansil Despite the progress made in the successful prediction of many classes of weakly-correlated topological materials, it is not clear whether a charge ordered topological state can exist in a two-dimensional (2D) material. Here, through first-principles modeling and analysis, we identify a 2×2 charge density wave (CDW) phase in monolayer 2H-NbSe2 that harbors coexisting quantum spin Hall (QSH) insulator, topological crystalline insulator (TCI), and topological nodal line (TNL) semimetal states. The topology in monolayer NbSe2 is driven by the formation of the CDW and the associated symmetry-breaking periodic lattice distortions and not via a pre-existing topology. Our finding of an emergent triple-topological state in monolayer 2H-NbSe2 will offer novel possibilities for exploring connections between different topologies and a unique materials platform for controllable CDW-induced topological states for potential applications in quantum electronics and spintronics. |
Monday, March 14, 2022 8:48AM - 9:00AM Withdrawn |
A60.00003: Electrical switching in a transtional metal dichalcogenide 1T-TiSe2 Josue Rodriguez, Luke Pritchard Cairns, Varun Menon, Shannon C Haley, James G Analytis Layered 2D transition metal dichalcogenides (TMDCs) host rich physical phenomena ranging from charge order to superconductivity. The ability to control and manipulate these phases by application of external pressure, gate voltage, twist-angle and optical stimulation enables vast opportunities for modern applications and basic research. Electical switcing of the charge order control is a novel direction towards the manipulation of these exotic phases. |
Monday, March 14, 2022 9:00AM - 9:12AM |
A60.00004: Origins of charge density wave sliding-based switching in layered 1T-TaS2 materials from first principles Vishal Ravi, Eran Maniv, Sophie F Weber, Shannon C Haley, Jonah B Haber, James G Analytis, Jeffrey B Neaton Recent experiments have shown that orthogonal current pulses alter the resistance of the low-temperature commensurate Star-of-David-type charge density wave (CDW) phase in bulk layered 1T-TaS2 [Maniv et al., unpublished]. Using first-principles density functional theory, we explore the origins of this resistive switching in terms of current-induced changes in metastable CDW stacking configurations, which alter their anisotropic conductivity. Calculating the anisotropy of band structures and transport properties for different stacking arrangements, as well as their energetics, allows us to build a hypothesis for resistivity switching through a repopulation of CDW stacking order. Our work leads to novel insights regarding the dynamics of CDWs in layered van der Waals materials and points to new energy-efficient ways to control logic and memory with an electric field. We acknowledge the DOE NPQC EFRC for funding and NERSC for computational resources. |
Monday, March 14, 2022 9:12AM - 9:24AM |
A60.00005: Evidence of mixed dimensionality and decoupled charge-lattice orders in layered TaTe2 Yi Lin, Maximilian Huber, Sangeeta Rajpurohit, Yanglin Zhu, Khalid Siddiqui, Daniel H Eilbott, Ping Ai, Jonathan D Denlinger, Zhiqiang Mao, Liang Tan, Alessandra Lanzara Charge and lattice orders are generally coupled in charge density wave (CDW) materials and share identical order wavevectors. Although this situation is usually satisfied in a large class of 2D materials, it comes short in describing the so called CDW-like phase transition in layered tantalum ditelluride (TaTe2), accompanied by anomalous low temperature transport properties and a periodic lattice distortion. Here we combine angle-resolved photoemission spectroscopy (ARPES) and low energy electron diffractions (LEED) to directly access the charge and lattice in TaTe2 to understand the CDW-like phase transition. We find evidence for the role of mixed dimensionality together with anomalous entanglements between the charge and lattice orders. We will discuss these results in the general contest of CDW phase transitions and show how our findings provide a new platform and principles for engineering complex orders in 2D materials. |
Monday, March 14, 2022 9:24AM - 9:36AM |
A60.00006: Symmetries of charge density wave states in AV3Sb5 Kagome compounds Turan Birol, Morten Holm Christensen, Brian M Andersen, Rafael M Fernandes Vanadium based Kagome metals AV3Sb5 undergo structural phase transitions driven by instabilities at the boundary of their hexagonal Brillouin zones. First principles calculations predict these instabilities to have wavevectors at the M and L points, as well as the U line connecting them. There is a large number of possible low symmetry crystal structures, and the ground state structure is still heavily debated. We perform an analysis of the crystal structure of AV3Sb5 compounds using a combination of group theory and density functional theory calculations. We determine the form of the crystal Hamiltonian, discuss the effects of the unique trilinear couplings, and sketch possible phase diagrams with multiple symmetry-broken phases. |
Monday, March 14, 2022 9:36AM - 9:48AM |
A60.00007: Time-reversal symmetry-breaking, nematicity, and charge-density wave order in the AV3Sb5 kagome metals Morten Holm Christensen, Turan Birol, Brian M Andersen, Rafael M Fernandes The family of metallic kagome compounds AV3Sb5 (A=K, Rb, Cs) was recently discovered to exhibit both superconductivity and charge-density wave (CDW) order. Density functional theory shows that phonon modes from both the M- and L-points in the Brillouin zone become unstable near the CDW transition. Low-energy models also support closely competing real and imaginary CDW orders. Motivated by these results, we construct a Landau free energy for the coupled CDW orders. In addition to the usual biquadratic coupling, we also find unusual trilinear and quadrilinear couplings. As a result, the phase diagram exhibits a rich landscape with multiple novel phenomena appearing due to the mixing of closely competing instabilities. We find both nematic and non-nematic phases that break time-reversal symmetry and that lead to the experimentally observed quadrupling of the unit cell. Interestingly, while the iCDW nematic phase does not exhibit an induced dipole moment, its non-nematic iCDW counterpart does. To provide a guide for scattering experiments we classify the space groups of the stable phases and explore additional experimental signatures that can help pinpoint the precise nature of the charge-ordered phase observed in the kagome metals. |
Monday, March 14, 2022 9:48AM - 10:00AM |
A60.00008: Exploring the Interplay Between Pressure, Strain, and Charge Density-Waves in CsV3Sb5 Ethan T Ritz, Rafael M Fernandes, Turan Birol The metallic Kagome compound CsV3Sb5 has been shown to exhibit pressure-dependent superconducting domes, as well as charge order. However, a complete understanding of how these properties are coupled to crystal symmetry and electronic structure remains elusive. By using density functional theory to explore how perturbations such as hydrostatic pressure and uniaxial strain give rise to changes in the electronic structure, we shed new light on the competition between different patterns of charge density wave ordering in this system, with potential implications for the superconducting behavior. Close attention is paid to how different charge orderings relate to the density of states at the Fermi level and the van Hove singularities at higher energies, as well as to changes in the structural properties. |
Monday, March 14, 2022 10:00AM - 10:12AM |
A60.00009: Electronic ground state evolution of two-dimensional transition metal dichalcogenide alloys throughout the metal-semiconductor transition Wen Wan, Paul L Dreher, Rishav Harsh, Miguel M Ugeda Transition metal dichalcogenide (TMD) alloys offer unprecedented versatility to engineer 2D materials with tailored properties for specific purposes. These include the unique opportunity to explore novel structural and electronic phase transitions in two dimensions (2D). In this work, we report on the atomic-scale evolution of the electronic ground state of a monolayer of Nb1-δ MoδSe2 with 0 < δ < 1 by means of low-temperature (300 mK) scanning tunneling microscopy/spectroscopy (STM/STS). In particular, we first investigate the atomic and low-energy electronic structure of this 2D alloy throughout the metal to semiconductor transition from the monolayer of NbSe2 to the monolayer of MoSe2. Our STS measurements enable to extract the effective doping of Mo impurities, the bandgap evolution as well as the band shifts. Furthermore, we probe the existence and properties of collective electronic phases (charge density wave (CDW) and superconductivity) to demonstrate a remarkable robustness against impurities. Our results paint a clear and detailed picture of the evolution of the electronic structure in 2D TMD alloys, which is of upmost relevance for future 2D materials' design. |
Monday, March 14, 2022 10:12AM - 10:24AM |
A60.00010: Proximity effects on the charge density wave order and superconductivity in single-layer NbSe2 Rishav Harsh, Paul L Dreher, Wen Wan, Alla Chikina, Marco Bianchi, Haojie Guo, Samuel Manas, Eugenio Coronado, Antonio Martinez-Galera, Philip Hofmann, Jill A Miwa, Miguel M Ugeda Metallic transition metal dichalcogenides (TMDs) exhibit a rich variety of electronic phases. One of the factor influencing these phases is the presence of the substrate, as it triggers "proximity effects" on the 2D material such as screening, charge transfer, hybridization, strain, etc. In this work, we provide a comparative assessment of the impact of different substrates on the CDW and SC phases as well as the electronic structure of a model correlated 2D material. In particular, we study the electronic ground state of high-quality SL-NbSe2 grown by molecular beam epitaxy (MBE) on four substrates-BLG/SiC(0001), SL-h-BN/Ir(111), Au(111) and bulk WSe2. By combining low-temperature (340 mK) scanning tunneling microscopy/spectroscopy (STM/STS) and angle-resolved photoemission spectroscopy (ARPES), we compare their respective electronic structure. |
Monday, March 14, 2022 10:24AM - 10:36AM |
A60.00011: A new microscopic theory on charge density wave phases in transition metal dichalcogenides Changwon Park Patterns and periods of charge density waves (CDW) in transition metal dichalcogenides have rich phase diagrams depending pressure, temperature, metal intercalation, or chalcogen alloying. The phase diagrams have been explained by phenomenological Landau free energy models pioneered by McMillan, Nakanishi and Shiba. In this talk, I will present a new microscopic theory for the phase diagrams by devising the suitable interatomic potentials. From first-principles calculation, we can extract the desired interatomic potentials to construct the lattice distortion energy in a reciprocal space from which temperature-dependent phase diagrams including lattice-incommensurate structures can be explicitly obtained. We successfully reproduce the experimental phase diagrams displaying commensurate lock-in, stripe phase, and atomic structure of incommensurate charge density wave, if name a few. Our microscopic theory provides us with straightforward interpretations of several CDW phases and deepens our understanding of the phase transitions between them. |
Monday, March 14, 2022 10:36AM - 10:48AM |
A60.00012: Pseudogap in a crystalline insulator doped by disordered metals Do Yun Park, Sae Hee Ryu, Minjae Huh, Keun Su Kim The electronic structure of a crystalline solid can be described based on the periodic order of constituent atoms, but little is known about how it changes in the presence of disorder. Back in the 1960s, theoretical models for the band structure of disordered systems, such as a liquid or a glassy solid, was formulated. [1] However, the key feature of theoretical models, the back-bending dispersion and pseudogap, has remained unobserved experimentally. In this talk, we will report the discovery of such features in black phosphorus whose surface is decorated by alkali-metal dopants (Na, K, Rb, Cs) with a liquid-like spatial distribution. Then, the doped electrons in black phosphorus are subject to multiple scattering by the effect of ionized dopants, modifying the band structure to that of liquid metals. Using angle-resolved photoemission spectroscopy, we observed the back-bending dispersion and pseudogap as a consequence of wavenumber renormalizations in the presence of short-range order. [1] |
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