Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session B43: Charge Density WavesLive
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Sponsoring Units: DCMP Chair: Harikrishnan Nair, University of Texas, El Paso |
Monday, March 15, 2021 11:30AM - 11:42AM Live |
B43.00001: Electron-Phonon Interactions in Flat Band Systems Chunhan Feng, Richard Theodore Scalettar Existing Quantum Monte Carlo studies have investigated the properties of fermions on a Lieb lattice interacting with an on-site, or near-neighbor electron-electron coupling. Attention has focused on the interplay of such interactions with the macroscopic degeneracy of local zero energy modes, from which Bloch states can be formed to produce a flat band in which energy is independent of momentum. The resulting high density of states, in combination with the Stoner criterion, suggests that there should be pronounced instabilities to ordered phases. Indeed, a theorem by Lieb rigorously establishes the existence of ferrimagnetic order. Here we study the charge density wave phases induced by electron-phonon coupling on the Lieb lattice, as opposed to previous work on electron-electron interactions. Our key result is the demonstration of charge density wave phases at one-third and two-thirds fillings, characterized by long-range density density correlations between doubly occupied sites on the minority or majority sublattice, and an accompanying gap. We also compute the transition temperature to the ordered phase as a function of the electron-phonon coupling. |
Monday, March 15, 2021 11:42AM - 11:54AM Live |
B43.00002: A potential all-electronic route to the charge-density-wave phase in monolayer vanadium diselenide Matthew Trott, Christopher Hooley The transition metal dichalcogenides offer significant promise for the tunable realisation and application of correlated electronic phases. However, tuning their properties requires an understanding of the physical mechanisms underlying their experimentally observed ordered phases, and in particular the extent to which lattice vibrations are a necessary ingredient. Here we present a potential mechanism for charge-density-wave formation in monolayers of vanadium diselenide in which the key role at low energies is played by a combination of electron-electron interactions and nesting. The competition between superconducting and density-wave fluctuations as sections of the Fermi surface are tuned to perfect nesting leads to charge-density-wave order when the effective Heisenberg exchange interaction is comparable to the effective Coulomb repulsion, and $d$-wave superconductivity when all effective interactions are purely repulsive. We discuss the possible role of lattice vibrations in enhancing the effective Heisenberg exchange during the earlier stages of the renormalisation group flow. |
Monday, March 15, 2021 11:54AM - 12:06PM Live |
B43.00003: Enhanced Low-Temperature Thermoelectric Performance in (PbSe)1+δ(VSe2)1 Heterostructures due to Highly Correlated Electrons in Charge Density Waves Yu Wang, Danielle M. Hamann, Dmitri Leo M. Cordova, Jihan Chen, Bo Wang, Lang Shen, Zhi Cai, Haotian Shi, Evguenia Karapetrova, Indu Aravind, Li Shi, David C. Johnson, Steve Cronin We explore the effect of charge density wave (CDW) on the in-plane thermoelectric transport properties of (PbSe)1+δ(VSe2)1 and (PbSe)1+δ(VSe2)2 heterostructures. In (PbSe)1+δ(VSe2)1 we observe an abrupt 86% increase in the Seebeck coefficient, 245% increase in the power factor, and a slight decrease in resistivity over the CDW transition. This behavior is not observed in (PbSe)1+δ(VSe2)2 and is rather unusual compared to the general trend observed in other materials. The abrupt transition causes a deviation from the Mott relationship through correlated electron states. Raman spectra of the (PbSe)1+δ(VSe2)1 material show the emergence of additional peaks below the CDW transition temperature associated with VSe2 material. Temperature-dependent in-plane X-ray diffraction (XRD) spectra show a change in the in-plane thermal expansion of VSe2 in (PbSe)1+δ(VSe2)1 due to lattice distortion. The increase in the power factor and decrease in the resistivity due to CDW suggest a potential mechanism for enhancing the thermoelectric performance at the low temperature region. |
Monday, March 15, 2021 12:06PM - 12:18PM Live |
B43.00004: Anisotropic Resistance and Slow Time Scale Physics in Pt-Doped 1T-TiSe2 Nicholas Mazzucca, Oscar R Avalos-Ovando, Dongying Wang, Emilia Morosan, Kenji Watanabe, Takashi Taniguchi, Chun Ning Lau, Nandini Trivedi, Marc Bockrath Electronic correlations can give rise to variety of insulating phases, ranging from Mott insulators [1] to spontaneously symmetry broken ground states [2]. Recently, Pt-doped 1T-TiSe2 has been shown to produce a new phase, interpreted previously in the context of the formation of an array of highly interacting one dimensional channels at sufficiently low temperatures [3]. Here, we present angle-dependent transport measurements on few-layer Pt-doped 1T-TiSe2 at 5% Pt doping. A strongly anisotropic in-plane resistance is observed which can be tuned by up to 2 orders of magnitude below the charge density wave transition temperature Tcdw ~ 200K. At the same time, the development of a nontrivial phase response of the electrons at ultralow frequencies on the order of 10Hz is observed. Our results are discussed in the context of an anisotropically pinned charge density wave, and possible connections to the previously reported model of one dimensional channels are made. |
Monday, March 15, 2021 12:18PM - 12:30PM Live |
B43.00005: Strange metal transport from pinned charge density waves Blaise Gouteraux, Luca V Delacretaz, Sean Hartnoll, Anna Karlsson, Andrea Amoretti, Daniel Arean, Daniele Musso In this talk, I will describe the effects of weak disorder on the hydrodynamics of incommensurate charge density waves, focusing on transport properties. Using gauge-gravity duality allows to uncover a universal relation between the pinning frequency of the phason and its decay rate. I will comment on possible connections to transport in the strange metallic phase of cuprate high Tc superconductors, where charge density fluctuations may play an important role. This talk is based on Amoretti et al, Phys. Rev. Lett. 123, 211602 (2019), and Delacrétaz et al, SciPost Phys. 3, 025 (2017) and Phys. Rev. B 96, 195128 (2017) . |
Monday, March 15, 2021 12:30PM - 12:42PM Live |
B43.00006: Study of Meta-stable States and Multiple Charge Orderings in La1/3Sr2/3FeO3 Using First-principles Nam Nguyen, Vijay Ramdin Singh, Hyowon Park La1/3Sr2/3FeO3 is a strongly correlated material exhibiting the strong interplay between spin, charge, and lattice degrees of freedom. It is an antiferromagnetic Mott insulator at low temperature below 200K accompanying a charge ordering with the Fe-O bond disproportionation. The charge ordering driven by magnetism shows the Fe3+/Fe5+/Fe3+ structure along the [111] direction and it disappears above 200K as the magnetic order is suppressed. Using first-principles calculations, we identify meta-stable states which can occur near the critical temperature. We compute the energy path along the meta-stable states using the nudged elastic band method and find multiple charge ordering states with competing energetics. Those multiple charge orders exhibit distinct structural distortions and the phase of charge order parameter is locked with the phase of spin order parameter. Our results can provide an insightful explanation to the slow dynamics of this material observed in the ultra-fast experimental measurement. |
Monday, March 15, 2021 12:42PM - 12:54PM Live |
B43.00007: Terahertz Time-Domain Magnetospectroscopy of La0.875Sr0.125MnO3 Fuyang Tay, Jiaming He, Nicolas Marquez Peraca, Xinwei Li, Andrey Baydin, Jianshi Zhou, Junichiro Kono Lanthanum strontium manganite (La1-xSrxMnO3 or LSMO) has attracted considerable interest over the last few decades due to its rich electronic phase diagram. The strong interplay among the charge, spin, orbital, and lattice degrees of freedom are believed to be behind the various phases that these compounds exhibit, but a microscopic understanding has been elusive. In particular, it is not understood what causes the metal-insulator transition at low temperatures in underdoped LSMO (0.1<x<0.15). Previous neutron and X-ray diffraction measurements suggested the existence of certain charge and orbital ordering in the low-temperature phase. Here we study different phases of La0.875Sr0.125MnO3 as a function of temperature and magnetic field via THz time-domain magnetospectroscopy. Optical conductivity spectra exhibited characteristic metallic or insulating behaviors in the different phases examined. We observed the emergence of a new collective mode in the insulator phase at the lowest temperatures, which shifts with the applied magnetic field. These measurements provide significant new insights into the underlying mechanism of the metal-insulator transition in the underdoped LSMO. |
Monday, March 15, 2021 12:54PM - 1:06PM Live |
B43.00008: Bypassing the Structural Bottleneck in the Ultrafast Melting of Electronic Order Lexian Yang, Michael Bauer, Kai Rossnagel Impulsive optical excitation generally results in a complex non-equilibrium electron and lattice dynamics that involves multiple processes on distinct timescales, and a common conception is that for times shorter than about 100 fs the gap in the electronic spectrum is not seriously affected by lattice vibrations. Here, however, by directly monitoring the photo-induced collapse of the spectral gap in a canonical charge-density-wave material, the blue bronze Rb0.3MoO3, we find that ultrafast (about 60 fs) vibrational disordering due to efficient hot-electron energy dissipation quenches the gap significantly faster than the typical structural bottleneck time corresponding to one half cycle oscillation (about 315 fs) of the coherent charge-density-wave amplitude mode. This result not only demonstrates the importance of incoherent lattice motion in the photo-induced quenching of electronic order, but also resolves the perennial debate about the nature of the spectral gap in a |
Monday, March 15, 2021 1:06PM - 1:18PM Live |
B43.00009: Langevin Simulation of Half-filled Cubic Holstein Model Benjamin Cohen-Stead, Chuang Chen, Kipton Marcos Barros, Zi Yang Meng, Richard Theodore Scalettar, George Batrouni Over the past several years, reliable Quantum Monte Carlo results for the charge density wave transition temperature Tcdw of the half-filled two dimensional Holstein model in square and honeycomb lattices have become available for the first time. Exploiting the further development of numerical methodology, here we present results in three dimensions, which are made possible through the use of Langevin evolution of the quantum phonon degrees of freedom. In addition to determining Tcdw from the scaling of the charge correlations, we also examine the nature of charge order at general wave vectors for different temperatures, couplings, and phonon frequencies, and the behavior of the spectral function and specific heat. |
Monday, March 15, 2021 1:18PM - 1:30PM Live |
B43.00010: Interplay of hot electron and phonon dynamics in 1T-VSe2 probed by time- and angle-resolved photoemission spectroscopy Paulina Majchrzak, Sahar Pakdel, Deepnarayan Biswas, Alfred Jones, Klara Volckaert, Igor Markovic, Federico Andreatta, Raman Sankar, Chris Jozwiak, Eli Rotenberg, Aaron Bostwick, Charlotte Sanders, Yu Zhang, Gabriel Karras, Richard T. Chapman, Adam Wyatt, Emma Springate, Jill A. Miwa, Philip Hofmann, Philip King, Nicola Lanata, Young Jun Chang, Søren Ulstrup The charge density wave (CDW) phase of bulk 1T-VSe2 gives rise to only subtle spectroscopic signatures [1-2], leaving unresolved the debate about dominant interactions driving the transition [3]. Here, we optically excite this material with an intense infrared femtosecond pulse, taking it out of its equilibrium CDW state, and probe the evolution of the transient quasiparticle dispersion with time- and angle-resolved photoemission spectroscopy. By monitoring the relaxation of light-induced hot electrons, we extract the time-dependent hot carrier temperature and find that the excited electrons reach a metastable thermal equilibrium with a strongly-coupled optical phonon mode on the timescale of 200 fs. The increase in hot phonon population available to scatter with photoholes leads to an increased linewidth of quasiparticle bands across the entire valence spectrum. We elucidate the role of electron-phonon interactions on the dynamics in this system and discuss the implications of our observations for the response to strong optical excitation in related CDW systems. |
Monday, March 15, 2021 1:30PM - 1:42PM Live |
B43.00011: Experimental realization of a transient highly-metallic inverted-charge-density-wave state in 1T-TaSe2 Yingchao Zhang, Xun Shi, Mengxue Guan, Wenjing You, Yigui Zhong, Tika Ram Kafle, Yaobo Huang, Hong Ding, Michael Bauer, Kai Rossnagel, Sheng Meng, Henry C Kapteyn, Margaret Murnane Charge density wave (CDW) materials are characterized by a periodic lattice distortion and an associated charge density modulation. A femtosecond laser pulse could coherently excite the amplitude mode, to steer the material into thermally inaccessible states and alter the electron-phonon interactions. Combining time- and angle-resolved photoemission spectroscopy and time-dependent density functional theory simulations, we uncover a new transient inverted CDW state in photoexcited 1T-TaSe2. This novel CDW state is accessed by over-driving the periodic star-of-David lattice distortion during the amplitude mode oscillation. The dynamic band structure indicates that the Ta 5d band width is maximum for the normal state, while it is reduced for both the usual CDW state and the inverted CDW state, which is associated with a dramatic change in the momentum-dependent electron-phonon coupling. Another important observation is that the inverted CDW state has more density of state at the Fermi level than the normal state. Our results demonstrate how ultrafast lasers can be used to generate unique lattice distortions and manipulate band- and mode-projected electron-phonon couplings. |
Monday, March 15, 2021 1:42PM - 1:54PM Live |
B43.00012: Quantum Hall charge density waves under anisotropy: from first-order to continuoustransitions Yuchi He, Kang Yang, Mark Oliver Goerbig, Roger Mong We investigate the quantum Hall charge density wave states in theN= 2 Landau level undermass anisotropy. In the absence of anisotropy, there are two first-order phase transitions betweenthe Wigner crystal, the 2-electron bubble phase, and the stripe phase. By adding mass anisotropy,our analytical and numerical studies show that the 2-electron bubble phase disappears and the stripephase significantly enlarges its domain in the phase diagram. Meanwhile, a regime of stripe crystalsthat may be observed experimentally is unveiled after the bubble phase gets out. Upon increase ofthe anisotropy, the energy of the phases at the transitions becomes progressively smooth as a functionof the filling. We conclude that all first-order phase transitions are replaced by continuous phasetransitions, providing a possible realisation of continuous quantum crystalline phase transitions. |
Monday, March 15, 2021 1:54PM - 2:06PM Live |
B43.00013: Charge Density Wave Melting in TiSe2 Maximilian Huber, Yi Lin, Robert A Kaindl, Alessandra Lanzara The emergence of charge density waves (CDW) in TiSe2 has been the subject of study for many years, with the driving mechanism for the CDW formation is still under debate. |
Monday, March 15, 2021 2:06PM - 2:18PM Live |
B43.00014: 3D-ΔPDF analysis of three-dimensional CDW compound (CaxSr1-x)3Rh4Sn13 Puspa Upreti, Matthew Krogstad, Lekh Poudel, Stephan Rosenkranz, Raymond Osborn, Omar Chmaissem A three-dimensional compound series (CaxSr1-x)3Rh4Sn13 has been identified as a promising system to understand the interplay between charge-density-waves (CDW) and superconductivity. The second order CDW transition temperature T* in this family can be fully suppressed with the substitution of Ca for Sr, giving rise to a Quantum Critical Point at x≈0.9 at ambient pressure. For a comprehensive understanding of the lattice instability connected to this CDW transition and superconductivity, diffuse scattering measurements were performed on single crystals of (CaxSr1-x)3Rh4Sn13 with (x=0, 0.1, 0.5, 0.6, 0.65, 0.7, 0.9) using x-ray diffraction. A 3D-ΔPDF analysis shows that there is an order-disorder transition at T*, with local distortions still present at higher temperature. |
Monday, March 15, 2021 2:18PM - 2:30PM Not Participating |
B43.00015: Dynamic Jahn-Teller effect on the nonequilibrium electronic transport in charge-density-wave systems Jong E Han Despite the well-known Peierls mechanism of the spontaneous symmetry-broken state of charge-density-wave (CDW) in (quasi-) one-dimensional solids, experimental verifications of the CDW have been quite elusive. One of the long-standing controversies has been the initial suppression of the current at a small but finite electric field of a few V/cm, whose energy scale has been many orders of magnitude smaller than the usual Landau-Zener interpretations. In this theoretical work, we investigate the dynamic effect of the Jahn-Teller (JT) phonons coupling of the left- and right-moving electrons and study how the initial suppression at a small electric field is related to the effectiveness of the JT effect in the large electric field limit. We compute the steady-state IV using the Keldysh Green's function method with the JT coupling effect in a conserving approximation with the nonequilibrium hot JT phonons dissipated into an Ohmic bath of background phonons. |
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