Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session K06: Hidden Order in URu2Si2 and Other Compounds |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Ryan Baumbach, National High Magnetic Field Laboratory Room: BCEC 109A |
Wednesday, March 6, 2019 8:00AM - 8:12AM |
K06.00001: Field-induced ferrohastatic order in cubic and tetragonal heavy fermion materials Rebecca Flint, John van Dyke, Milan Kornjaca Heavy fermion compounds with non-Kramers doublet ground states can realize a novel heavy Fermi liquid with spinorial hybridization ('hastatic' order) that breaks both single- and double-time reversal. Hastatic order was initially proposed to explain the hidden order in the tetragonal URu2Si2, which is stable in magnetic field up to 35T. Now several cubic Pr-"1-2-20" materials exhibit a suggestive heavy Fermi liquid stabilized in intermediate magnetic fields. In this talk, we develop a simple, yet realistic model of ferrohastatic order in both cubic and tetragonal symmetries, and elaborate its experimental signatures and behavior in field, where it is a good candidate to explain the observed heavy Fermi liquids. |
Wednesday, March 6, 2019 8:12AM - 8:24AM |
K06.00002: Kondo hybridization and enigmatic f-quasiparticles emerging from deep within the antiferromagnetic phase of USb2 Ioannis Giannakis, Justin Leshen, Mariam Kavai, Sheng Ran, Shanta Saha, Nicholas Butch, Pegor Aynajian Novel electronic phenomena frequently form in heavy fermion systems because of the f-electrons’ localized and itinerant nature. When magnetically ordered, the f moments are expected to be frozen and localized, decoupled from the Fermi surface. It remains ambiguous whether a Kondo-lattice can emerge from deep inside the magnetic phase or simply breaks down below TN. Using spectroscopic imaging with the scanning tunneling microscope complemented by neutron scattering, we probe the electronic states in the antiferromagnetic USb2 as a function of temperature. We visualize an antiferromagnetic gap at high temperatures (T<TN~200K) in which Kondo hybridization gradually develops below Tcoh~80K near the Fermi energy. At T*=45K we find an electronic transition through the abrupt emergence of non-trivial sharp 5f quasiparticles, whose appearance agrees with the sudden release of entropy seen in specific heat. Our findings demonstrate the emergence of Kondo physics from inside USb2's antiferromagnetic phase, spectroscopically establishing the dual nature of f-electrons, and reveal an enigmatic electronic transition, which may share connection with the ‘hidden order’ phase of URu2Si2. |
Wednesday, March 6, 2019 8:24AM - 8:36AM |
K06.00003: ARPES/STM study of the surface terminations and 5 f-electron character in URu2Si2 Wen Zhang Hidden order in URu2Si2 has remained a mystery that is now entering its fourth decade. The importance of resolving the nature of the hidden order has stimulated extensive research. Here we present a detailed characterization of different surface terminations in URu2Si2 by angle-resolved photoemission spectroscopy, in conjunction with scanning tunneling spectroscopy and dynamical mean-field theory calculations that may unveil a piece of this puzzle. The U-terminated surface is characterized by an electronlike band around the X point, while a holelike band characterizes the Si-terminated surface. We also investigate the temperature evolution of the electronic structure around the X point from 11 up to 70 K, and do not observe any abrupt change of the electronic structure around the coherence temperature (55 K). Our results suggest that surface terminations in URu2Si2 are an important issue to be taken into account in future work. |
Wednesday, March 6, 2019 8:36AM - 8:48AM |
K06.00004: Gaussian fluctuation corrections to a mean-field theory of complex hidden order in URu2Si2 Pengtao Shen, Maxim Dzero Hidden-order phase transition in the heavy-fermion superconductor URu2Si2 exhibits the mean-field-like anomaly in temperature dependence of heat capacity. Motivated by this observation, here we explore the impact of the complex order parameter fluctuations on the thermodynamic properties of the hidden order phase. Specifically, we employ the mean-field theory for the hidden order which describes the hidden order parameter by an average of the hexadecapole operator. We compute the gaussian fluctuation corrections to the mean-field theory equations including both the fluctuations due to "hidden order" as well as antiferromagnetic order parameters. We find that the gaussian fluctuations lead to the smearing of the second-order transition rendering it to become the first-order one. The strength of the first-order transition is weakly dependent on the strength of underlying antiferromagnetic exchange interactions. |
Wednesday, March 6, 2019 8:48AM - 9:00AM |
K06.00005: Pressure-Induced Rotational Symmetry Breaking in URu2Si2 Jaewon Choi, Oleh Ivashko, Nik Dennler, Markus Huecker, Dai Aoki, Karin von Arx, Simon Gerber, Olot Gutowski, Mark H Fischer, Joerg Strempfer, Martin v. Zimmermann, Johan Chang The heavy-fermion compound URu2Si2 has provided an excellent arena to study phase transition and related symmetry breaking in correlated electron system. Despite of relentless efforts for several decades, elucidating the nature of hidden order (HO) phase at 17.5 K still remains enigmatic. Even though the experimental evidences for both broken rotational [1] and chiral symmetry [2] were found recently, little is known about crystal structure of the system. Here, we report a hard x-ray diffraction study of the single crystal URu2Si2 under hydrostatic pressure. For pressure above 3.4 kbar, we found a rotational symmetry breaking from tetragonal to orthorhombic crystal structure with onset temperatures near 100 K. Contrast to recent x-ray diffraction study [3], the pressure-induced orthorhomicity is not coincided with the HO transition. Instead, its temperature-dependence suggests possible relevance with the antiferromagnetic (AF) order. This observation has not yet been predicted by theories describing an adiabatic continuity of a complex order parameter. Therefore, our findings provide new perspectives to the long-standing conundrum. |
Wednesday, March 6, 2019 9:00AM - 9:12AM |
K06.00006: Temperature T vs Os concentration x phase diagram for URu2-xOsxSi2 single crystals Alexander Breindel, Kalyan Sasmal, Naveen Pouse, Christian Wolowiec, Sheng Ran, M Brian Maple The compound URu2Si2 has attracted much interest due to its “hidden order” (HO) phase, whose order parameter has not been definitively determined after more than three decades of research on this compound. The substitution of isoelectronic Fe for Ru in URu2Si2 produces a transition from the HO phase to a large moment antiferromagnetic (LMAFM) phase, similar to what occurs under the application of pressure. This has been attributed to the “chemical pressure” associated with the substitution of the smaller Fe atom for Ru, which increases with Fe concentration. The substitution of isoelectronic Os for Ru also produces a transition from the HO to the LMAFM phase with increasing Os concentration. Since the substitution of Os, which is larger than Ru, generates a negative chemical pressure, this suggests other factors must be involved in the case of Os (e.g., spin-orbit coupling, increased hybridization due to increased spatial extent from Os d-orbitals). In this talk, we present the T vs x phase diagram, based on electrical resistivity, specific heat, magnetization, and thermal expansion measurements as a function of temperature and pressure, for Czochralski grown URu2-xOsxSi2 single crystals. |
Wednesday, March 6, 2019 9:12AM - 9:24AM |
K06.00007: Pressure tuning in URu2Si2-xPx Greta Chappell, David E Graf, Kevin Huang, Andrew Gallagher, Ryan Baumbach In an effort to elucidate the unknown hidden ordered state at T0 ~ 17.5 K in the heavy fermion compound URu2Si2, temperature dependent electrical resistivity measurements were performed on the electron doping chemical substitution series Si → P under quasi-hydrostatic pressures up to 21 kbar. Previous studies show that electron doping causes the HO to be rapidly suppressed towards zero temperature over a small x-range, after which there is a broad paramagnetic (PM) region that is eventually replaced by antiferromagnetic (AFM1) order at large x[1,2]. Our results indicate that, like x = 0, HO transforms to AFM2 at critical pressures that decrease with increasing x, while the PM and AFM1 states are robust against pressure. We will present the resulting T - x - P phase diagram and discuss the ordered states in the electronic phase space surrounding URu2Si2. |
Wednesday, March 6, 2019 9:24AM - 9:36AM |
K06.00008: Observation of the hybridization gap in different ground states of URu2-xFexSi2 and URu2Si2-xPx Shengzhi Zhang, Greta Chappell, Ryan Baumbach, Naveen Pouse, M Brian Maple, Laura H Greene, Wan Kyu Park Quasiparticle scattering spectroscopy (QPS) applied to heavy fermions utilizes a ballistic junction to probe how electrons scatter off strongly energy-dependent density of states in the bulk[1]. Our previous QPS study on URu2Si2-xPx[2] found that a hybridization gap opens regardless of the ground state ordering as it was also observed in the no-order region, consistent with earlier reports where a hybridization gap was observed to open well above the hidden order transition temperature in URu2Si2[1]. Fe substitution acts like the application of chemical pressure[3] and the resulting phase diagram closely resembles the case of hydrostatic pressure, providing a new opportunity to probe the coexistent/competing region. We will present conductance spectra as a function of temperature and chemical substitution and discuss the correlation between hybridization process and emergent ground states. |
Wednesday, March 6, 2019 9:36AM - 9:48AM |
K06.00009: Optical conductivity of URu2Si2-xPx from the hidden-order to the antiferromagnetic phase Alexandre Zimmers, Ricardo Lobo, Ryan Baumbach We report the optical spectroscopy of the URu2Si2-xPx heavy fermion chemical substitution series. For x=0, this material is the now well-studied URu2Si2 compound with a Kondo temperature of 370K. In this material, the hybridization between heavy f electrons with conduction electrons creates a crossover to a Kondo liquid state having coherent transport properties below 70K. At 17.5K, a second-order mean-field transition creates an electronically ordered state whose origin remains unknown, commonly called the hidden order (HO) phase. Finally below 1.5K an unconventional superconducting phase emerges. The HO phase disappears for x≥0.035 and, at much higher doping x>0.25, an antiferromagnetic phase (AFM) emerges at low temperature (TN~40K for x=0.28). |
Wednesday, March 6, 2019 9:48AM - 10:00AM |
K06.00010: Complex order above the Kondo Coherence temperature in UPt2Si2 and UCr2Si2 Ryan Baumbach, You Lai, Greta Chappell, David E Graf, Xin Yan, John A Mydosh For strongly correlated f-electron metals it is commonplace for exotic ordered states to occur at temperatures well below the Kondo coherence temperature. More unusual is for phase transitions to emerge from the incoherent f-electron lattice at elevated temperatures, where single ion Kondo physics and strong thermal fluctuations would naively be presumed to be dominant terms. This is despite the prevalence of structural/electronic instabilities in the isolated f-electron elements, where a leading example is plutonium which undergoes six structure changes and features novel behavior including negative thermal expansion in the delta phase. In this talk we will discuss results for two examples: UPt2Si2 and UCr2Si2. Both systems exhibit phase transitions near room temperature that may involve modulation of the lattice or charge density wave order. In addition, UCr2Si2 undergoes a structural phase transition near 210 K. We will focus on efforts to identify the order parameters for these phases. |
Wednesday, March 6, 2019 10:00AM - 10:12AM |
K06.00011: Possible structural quantum phase transition in UCr2-xRuxSi2 You Lai, Greta Chappell, David E Graf, Theo Siegrist, Jennifer Neu, Yan Xin, Ryan Baumbach We report an investigation of the structural, thermodynamic, and electrical transport properties of the chemical substitution series UCr2-xRuxSi2. UCr2Si2 is an unusual Kondo lattice metal that shows antiferromagnetism at TN = 27 K, a structural phase transition from tetragonal (I4/mmm) to triclinic (P) near Ts = 210 K, and a so-far unidentified phase transition near TM = 275 K. Cr → Ru substitution results both in expansion of the unit cell volume and filling of the d-shell, causes TN and TS to be suppressed to zero temperature near xcr ≈ 0.075 and 0.13, respectively. In contrast, TM disappears immediately with small amount of Ru. In the critical region, there is evidence for non-Fermi liquid behavior, (i) a weak logarithmic divergence in the electronic component of the heat capacity divided by temperature and (ii) a sub-quadratic temperature dependence of the electrical resistivity. Thus, we suggest that this may be a model system for studying a lattice instability at zero temperature, its relationship to a nearby antiferromagnetic quantum phase transition, and the resulting impact on electronic properties and lattice modes in a strongly correlated electron metal. |
Wednesday, March 6, 2019 10:12AM - 10:24AM |
K06.00012: Unveiling Hidden Orders: Magnetostriction as a Probe of Multipolar-Ordered States Adarsh S Patri, Akito Sakai, SungBin Lee, Arun Paramekanti, Satoru Nakatsuji, Yong-Baek Kim Symmetry broken phases involving higher order multipolar degrees of freedom are historically referred to as so-called “hidden orders”, due to the formidable task of detecting them with conventional probes. In this talk, we theoretically propose a novel and powerful means to directly probe higher-order symmetry breaking: magnetostriction. To that end, we focus on the family of Pr-based cage compounds with strongly correlated f-electrons, Pr(Ti,V,Ir)2(Al,Zn)20, whose low energy degrees of freedom are composed of purely higher-order multipoles. Employing a symmetry-constructed Landau theory of multipolar moments, we provide key scaling behaviours of the magnetostriction in a range of temperature regimes. These findings provide a way to have clear access to higher order multipolar moments. |
Wednesday, March 6, 2019 10:24AM - 10:36AM |
K06.00013: Sequential Localization and Strange-metal Behavior in a Multipolar Kondo System Silke Paschen, Ang Cai, Emilian Nica, Chia-Chuan Liu, Rong Yu, Kevin Ingersent, Qimiao Si Quantum criticality and beyond-Landau physics of Kondo destruction [1,2] in heavy fermion systems with multipolar degrees of freedom is attracting considerable interest. Recent experiments on the heavy fermion compound Ce3Pd20Si6 show evidence of two consecutive Fermi surface collapsing quantum critical points (QCP) as it is tuned from a paramagnetic to an antiferroquadrupolar (AFQ) and then to an antiferromagnetic (AFM) state [3]. We are able to understand this behavior by advancing a theory of sequential destruction of an SU(4) spin-orbital-coupled Kondo entanglement in an SU(4) Bose-Fermi Kondo model, which represents an effective model for a multipolar Kondo lattice system with Kugel–Khomskii interaction. As a function of coupling strength to the bosonic bath, we find that a generic trajectory in the parameter space contains two QCPs associated with the Kondo destruction of the orbital and spin degrees of freedom, respectively. For a Kondo lattice, this corresponds to two stages of Fermi surface jump, thus providing a natural understanding of the experimental findings. |
Wednesday, March 6, 2019 10:36AM - 10:48AM |
K06.00014: Switching the propagation vector of hidden-order phases in Ce3Pd20Si6 with a magnetic field Dmytro Inosov, Pavlo Portnichenko, Stanislav Nikitin, Andrey Prokofiev, Silke Buehler-Paschen Hidden-order phases that occur in a number of correlated f-electron systems are among the most elusive states of electronic matter. Their investigations are hindered by the insensitivity of standard physical probes, such as neutron diffraction, to the order parameter that is usually associated with higher-order multipoles of the f-orbitals. The heavy-fermion compound Ce3Pd20Si6 exhibits magnetically hidden order at subkelvin temperatures, known as phase II. Additionally, for magnetic field applied along the [001] cubic axis, another phase II′ was detected, but the nature of the II-II′ phase transition remained unclear. Here we use inelastic neutron scattering to demonstrate that this transition is associated with a switching in the propagation vector of the antiferroquadrupolar order from (111) to (100). Despite the absence of magnetic Bragg scattering in phase II′, its ordering vector is revealed by the location of an intense magnetic soft mode at the (100) wave vector, orthogonal to the applied field. At the II-II′ transition, this mode softens and transforms into quasielastic and nearly Q-independent incoherent scattering. Our experiment also reveals sharp collective excitations in the field-polarized paramagnetic phase, after phase II′ is suppressed in fields above 4 T. |
Wednesday, March 6, 2019 10:48AM - 11:00AM |
K06.00015: Theoretical X-ray spectroscopic study of 5f-electron signatures in actinide materials Wei-ting Chiu, Jian-Xin Zhu Actinide materials are not only important for power generation nowadays, but also exhibit interesting physical properties from the condensed matter physics perspective. The valence 5f electrons in early actinides are considered to be delocalized, while in the late actinides the 5f electrons show localized behavior. Studying the local moment and 5f-electron occupations will shed insight into the electronic behavior in these materials. X-ray absorption spectroscopy (XAS) and X-ray photoemission spectroscopy (XPS) have been powerful tools to reveal the valence electronic structure with the assistance from theoretical calculations. In this work, we build a single-impurity Anderson model for the materials, and use exact diagonalization method to calculate its eigenenergies and eigenstates. The X-ray spectra are obtained by employing Fermi’s golden rule. Comparing the theoretical spectra with the experimental results provides a way to determine the 5f electronic signatures of the actinide materials, helping us understand the 5f electronic correlation effects. |
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