Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session S61: Metal-Insulator Transition in 4d/5d SystemsFocus
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Sponsoring Units: DMP DCMP Chair: Tomohiro Takayama, Max Planck Inst Room: Mile High Ballroom 4B |
Thursday, March 5, 2020 11:15AM - 11:27AM |
S61.00001: Raman scattering from current-stabilized nonequilibrium phases in Ca2RuO4 Katrin Fuersich, Joel Bertinshaw, Paul L Butler, Maximilian Krautloher, Matteo Minola, Bernhard Keimer We used Raman light scattering to study the current-stabilized nonequilibrium semimetallic and metallic |
Thursday, March 5, 2020 11:27AM - 11:39AM |
S61.00002: Octahedral tilt driven Kondo lattice behavior with orbital-selective Mott transition of 4d Ca2-xSrxRuO4 Minsoo Kim, Junyoung Kwon, Daun Chung, Younsik Kim, Hanyoung Yoo, Jongkeun Jung, Beom Seo Kim, Mi Kyung Kim, Jonathan Denlinger, Moonsup Han, Takashi Mizokawa, yoshiyuki yoshida, Wonshik Kyung, Changyoung Kim The physics of heavy fermion (HF) state, which manifests in f-electron system [1], begins to germinate in d-orbital system, for example, in 3d single-orbital van der Waals ferromagnet, transition metal oxide(TMO) LiV2O4 and multi-orbital Fe based family [2, 3, 4]. However, the existence of the HF state and its underlying mechanism remain to be questionable in 4d multi orbital systems. Using angle-resolved photoemission spectroscopy (ARPES), we observe the HF state in orbital-selective Mott phase (OSMP) of 4d TMO, Ca2-xSrxRuO4. Upon entering OSMP (x<0.5), we observe a massive spectral weight transfer, a 100meV-orbital selective gap for dxy-originated γ and corresponding change in dxz/yz-originated β band while dxz/yz-originated α band remains hardly changed. With the temperature drop across a characteristic temperature T*, spectral weight transfer gradually occurs from lower to higher binding energy in β and γ bands. This possible Kondo lattice behavior can be well explained by the key role of the octahedral tilt driven d-band hybridization. Our work firstly, demonstrates the possible origin of the formation of the HF state from 4d TMOs with structural distortions, which expands the boundary of the HF-candidates to the 4d multi orbital systems. |
Thursday, March 5, 2020 11:39AM - 11:51AM |
S61.00003: electric control of the structural properties of spin-orbit coupled 4d ruthenate Ca2Ru0.97Mn0.03O4 Feng Ye, Christina Hoffmann, Hengdi Zhao, Gang Cao The unique competition between spin-orbit interaction (SOI) and Coulomb correlation (U) in 4d/5d oxides drives unusual physical behavior. Novel nonequilibrium phenomena can be further induced by external stimuli including intense synchrotron x-ray or electric current. In this talk, we report neutron diffraction study of the quasi-two-dimensional Mott Ca2Ru0.97Mn0.03O4, which shows dramatic reduction of the electric resistivity, suppression of the antiferromagnetic transition, and induction of new orbital order with critical current density of 0.15 A/cm2. Our in-situ structural characterization implies that the in-plane orthorhombicity diminishes with increasing current density, accompanied by the straightened of the Ru-O-Ru bonding angles. The temperature-current phase diagram establishes an intimate correlation between the lattice and electronic structure in this nonequilibrium, steady state driven by current. Our results shed light to the nature of the Mott-Insulator transition and provide key information for the emerging phenomena near the transition. |
Thursday, March 5, 2020 11:51AM - 12:27PM |
S61.00004: Metallic and non-metallic duality in the 4d pyrochlore Lu2Rh2O7 Invited Speaker: Alannah Hallas The 4d transition metal oxides exist in an intriguing regime where on-site Coulomb repulsion, the band width, and spin-orbit coupling can all have comparable magnitudes. While spin-orbit coupling for these 4d systems is reduced as compared to their 5d counterparts, it is still strong enough to generate exotic magnetic and electronic states. In this talk, we introduce Lu2Rh2O7, a new cubic pyrochlore oxide based on 4d5 Rh4+ with properties that defy simple categorization. Both magnetic susceptibility (χP = 7.6×10−4 emu/molRh) and heat capacity measurements (γ = 21.8(1) mJ/molRhK2) indicate that this material is a strongly correlated metal and yet electrical resistivity measurements show decidedly non-metallic behavior. Furthermore, although the magnitude of the resistivity is that of a semiconductor (1 Ω-cm), the temperature dependence does not obey any conventional form. The magnetic properties of this material are also enigmatic; if this material is non-metallic, then one would expect 4d5 Rh to carry an S = ½ magnetic moment and yet magnetic susceptibility and muon spin relaxation measurements show no evidence for local moments down to 2 K. We therefore propose that Lu2Rh2O7 may be the prototype for an entirely new class of non-Fermi liquids. |
Thursday, March 5, 2020 12:27PM - 12:39PM |
S61.00005: Anomalous Hall effect from strained-induced magnetic multipoles in antiferromagnetic material Jeongkeun Song, Taekoo Oh, Woojin Kim The origin of anomalous Hall effect (AHE) in magnetic materials has been a central theme of condensed matter physics for a century. In ferromagnetic materials, the origin of AHE is from the magnetization. [1] On the other hand, the large AHE in antiferromagnetic Mn3Sn without large magnetization was observed and its origin reamins elusive.[2] Recent theoretical study suggested that the hidden magnetic multipoles formed by the spin clusters can induce the large AHE in antiferromagnet. [3] Here, we establish the comprehensive connection between the large AHE in antiferromagnetic in-situ pyrochlore iridate Nd2Ir2O7 thin film and strain-induced magnetic multipoles, T1-octupole. |
Thursday, March 5, 2020 12:39PM - 12:51PM |
S61.00006: Approaching the quantum critical point in a highly-correlated all-in-all-out antiferromagnet Yejun Feng, Yishu Wang, Dharmalingam Prabhakaran, Andrew T Boothroyd, Thomas F Rosenbaum All-in-all-out (AIAO) antiferromagnetic order in strongly spin-orbit-coupled 5d compounds can demonstrate exotic electronic phases and strongly-coupled quantum critical phenomena. Here we experimentally explore this scenario by directly tracing the AIAO spin order in Sm2Ir2O7 using resonant x-ray magnetic diffraction techniques under high pressure. We find that the magnetic order is suppressed at a critical pressure Pc=6.30 GPa, while the lattice symmetry remains in the cubic Fd-3m space group across the quantum critical point. Comparing pressure tuning and the chemical series R2Ir2O7 reveals that the suppression of the AIAO order and the approach to the spin-disordered state is characterized by contrasting evolutions of both the pyrochlore lattice parameter a and the trigonal distortion x. The former affects the 5d bandwidth, the latter the Ising anisotropy, and as such we posit that the opposite effects of pressure and chemical tuning lead to spin fluctuations with different Ising and Heisenberg character in the quantum critical region. Finally, we compare the iridates to AIAO spin order in osmate analogues, where spin fluctuations, lattice breathing modes, and quasiparticle excitations all interact in the quantum critical region. |
Thursday, March 5, 2020 12:51PM - 1:03PM |
S61.00007: Geometric Magnetic Frustration in Y2-xBixRu2O7 Pyrochlores across the Metal-Insulator transition Sarah Dunsiger, Sang-Wook Cheong, Kim Hooh Chow, Martin H Dehn, Shayan Gheidi, Namjung Hur, Kee Hoon Kim, Graeme Luke, Gerald Morris, Timothy Munsie, Jeff Sonier, Shyam Sundar Systems based on a triangular or pyrochlore lattice of corner sharing tetrahedra with nearest neighbor antiferromagnetic exchange interactions are the archetypal examples of geometric magnetic frustration, offering a means of accessing novel ground states. Magnetic systems based on 4d and 5d transition metal ions on the pyrochlore lattice offer a unique opportunity to explore the exotic ground states which potentially arise when the electron-electron Coulomb interaction, electronic bandwidth and spin orbit coupling are all of comparable magnitude. I will describe magnetization and muon spin relaxation investigations of a series of 4d Ru4+ based pyrochlores, which may be controllably tuned through a metal insulator transition, providing insight into the magnetic correlations as these finely balanced systems evolve from a localized to itinerant spin character. |
Thursday, March 5, 2020 1:03PM - 1:15PM |
S61.00008: Electrically driven inhomogeneous phase transition in CuIr2S4 Ahmed Ali, Dasharath Adhikari, Ali M Alsaqqa, Colin P Kilcoyne, Nobuhiro MATSUMOTO, Sambandamurthy Ganapathy Comparable energy scales of dominant interactions determining electronic phases and relatively smaller energy barrier separating different phases makes 5d electronic systems sensitive to an external perturbation (e.g. temperature, electric field, strain). CuIr2S4, a 5d transition metal compound with spinel structure, shows a hysteretic metal-insulator transition at Tc ~ 231 K (on cooling) accompanied with crystal symmetry lowering from high-temperature cubic (metallic) to low-temperature tetragonal (insulating) phase. The system also exhibits electric field-driven hysteretic switching from insulating to metallic phase below Tc. Transport and resistance noise spectroscopy were carried out: at temperatures well below Tc, the transition is characterized by a single abrupt switching and the power spectral density (PSD) of the noise varies smoothly across the transition. Approaching Tc, on the other hand, switching happens with multiple, step-like jumps and the PSD is found to increase significantly. The melting of long-range charge ordering near Tc likely increases the local inhomogeneity thereby resulting in increased PSD. Results will be discussed in the context of microscopic conduction mechanisms across thermal and electrical driven transitions in strongly correlated systems. |
Thursday, March 5, 2020 1:15PM - 1:27PM |
S61.00009: Local orbital degeneracy lifting as a precursor to an orbitalselective Peierls transition Emil Bozin, Weiguo Yin, Robert Koch, Milinda Abeykoon, Yew San Hor, Hong Zheng, Hechang Lei, Cedomir Petrovic, John Mitchell, Simon J L Billinge Fundamental electronic principles underlying all transition metal compounds are the symmetry and filling of the d-electron orbitals and the influence of this filling on structural configurations and responses. Here we use a sensitive local structural technique, x-ray atomic pair distribution function analysis, to reveal the presence of fluctuating local-structural distortions at high temperature in one such compound, CuIr2S4. We show that this hitherto overlooked fluctuating symmetry-lowering is electronic in origin and will modify the energy-level spectrum and electronic and magnetic properties. The explanation is a local, fluctuating, orbital-degeneracy-lifted state. The natural extension of our result would be that this phenomenon is likely to be widespread amongst diverse classes of partially filled nominally degenerate d-electron systems, with potentially broad implications for our understanding of their properties. |
Thursday, March 5, 2020 1:27PM - 1:39PM |
S61.00010: The spin-orbit coupling driven spectral and magnetic properties of LiOsO3:
A DFT+DMFT study Severino Adler, Daniel Springer, Bongjae Kim, Peitao Liu, Andreas Hausoel, Cesare Franchini, Giorgio Sangiovanni, Alessandro Toschi Experiments on the 5d-Osmium oxide perovskite LiOsO3 have revealed surprising physical properties. In contrast to expectations and to the chemically similar material NaOsO3, LiOsO3 is never magnetic. Further, its optical properties show a bad metallic behaviour, with a quickly decreasing Drude peak as a function of T [1], as in the 3d-oxide V2O3 [2]. A possible origin of this unexpected physics might be the interplay between electronic correlations and spin-orbit coupling (SOC) in this 5d compound. Therefore, we performed a paramagnetic, non SOC dependent DFT and a magnetic DMFT calculation, where we tuned the atomic SOC in the Os t2g manifold. Without atomic SOC, we find a strong long-range G-type antiferromagnetic order. Turning on atomic SOC antiferromagnetism is gradually suppressed, vanishing at a SOC strength of about 600 meV. This strongly suggests that atomic SOC plays a pivotal role in determining the magnetic properties of osmates. |
Thursday, March 5, 2020 1:39PM - 1:51PM |
S61.00011: Survived Jeff = 3/2 state under pressure and its implication for unconventional superconductivity in GaTa4Se8: LDA+DMFT study Min Yong Jeong, Jae-Hoon Sim, Hyeong Jun Lee, Ara Go, Myung Joon Han The lacunar spinel GaTa4Se8 is the first established example of Jeff = 3/2 Mott insulator. By applying pressure, it undergoes insulator-to-metal and superconducting transition. In order to understand the nature of this intriguing metallic phase and its possible relation to superconductivity, we performed the LDA+DMFT (local density approximation + dynamical mean-field theory) calculations as a function of pressure and with spin-orbit coupling taken into account. It is found that, even at high pressure corresponding to the metallic and superconducting phase, Jeff = 3/2 is well identified, indicating the novel nature of the superconductivity observed in this material. Possibilities of topological superconductivity and the spin-freezing superconductivity will be discussed. |
Thursday, March 5, 2020 1:51PM - 2:03PM |
S61.00012: Magnetic impurity behavior in a gapless quantum spin liquid: single-layer 1T-TaSe2 Yi Chen, Wei Ruan, Jinwoong Hwang, Meng Wu, Shujie Tang, Hyejin Ryu, Steven Louie, Patrick A Lee, Zhixun Shen, Sung-Kwan Mo, Michael F Crommie Quantum spin liquids are a novel state of matter predicted to arise in quantum antiferromagnets where geometric frustration and quantum fluctuations are strong enough to prevent a magnetically ordered ground state. At half filling, fractional spin-carrying excitations termed spinons dominate the low-energy physics. Here we present scanning tunneling microscopy studies of the behavior of magnetic adatoms deposited onto the quantum spin liquid candidate single-layer 1T-TaSe2. Spectroscopic imaging of pristine single-layer 1T-TaSe2 reveals long-wavelength density modulations at the Hubbard band energies consistent with a spinon Fermi surface instability as predicted by theory. Magnetic atoms deposited onto the 1T-TaSe2 surface bind at different sites in the star-of-David unit cell and exhibit distinct spectroscopic features near the Hubbard band edges. One possible explanation for the observed behavior is exchange coupling between magnetic adatoms and itinerant spinons. |
Thursday, March 5, 2020 2:03PM - 2:15PM |
S61.00013: Spectroscopic signatures of Quasi One-Dimensional Crystallization at Domain Walls in the Mott Insulator TaS2 Anuva Aishwarya, Sean Howard, Bikash Padhi, Lihai Wang, Sang-Wook Cheong, Philip Phillips, Vidya Madhavan A tunable Mott state is fortuitous as it is a model system to study emergent phenomena due to broken symmetries like superconductivity, novel magnetic order and charge order, as a Mott band is tuned across Fermi energy (EF). In this work, we use scanning tunneling microscopy at 4K to study the Mott insulator, TaS2. Charge density wave domain walls in TaS2 create band tuning such that part of the lower Hubbard band crosses the EF, creating a mobile pool of charge near the domain walls. STM spectroscopic maps show that these charges crystallize into unexpected 1D patterns. To distinguish the charge patterns from ordinary bound states, we carry out noise spectroscopy measurements and find that the 1D patterns show distinct telegraphic noise signatures indicative of a fragile condensed state. Combined with the large ratio of Coulomb to kinetic energies in this system, our data and calculations are consistent with the formation of a short-range, fragile charge order like an incipient Wigner crystal. The observation of crystallization in a strongly correlated regime makes TaS2 a promising system for exploiting the charge and spin order in quasi 1D systems. |
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