Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session F20: URu2Si2 and Other Actinides |
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Sponsoring Units: DCMP GMAG Chair: Pegor Aynajian, SUNY Binghamton Room: 280 |
Tuesday, March 14, 2017 11:15AM - 11:27AM |
F20.00001: Collective Modes in the Hidden Ordered Phase of URu2Si2 Peter Riseborough We examine the form of the collective modes expected for a spin-dependent orbital density wave phase of the Under screened Anderson Lattice Model, which has been proposed as describing the Hidden Ordered Phase of URu2Si2. We discuss the magnetic field dependence of the phase diagram and the magnetic nematicity that occurs be low the HO transition. We calculate the collective modes associated with the HO phase transition and discuss possible experimental consequences. [Preview Abstract] |
Tuesday, March 14, 2017 11:27AM - 11:39AM |
F20.00002: Non-Equilibrium Effects on the Hidden Order of Microstructured URu$_2$Si$_2$ Laurel E Winter, Philip J. W. Moll, B. J. Ramshaw, Arkady Shekhter, N. Harrison, Eric D. Bauer, Ross D. McDonald Despite extensive studies on the heavy-fermion URu$_2$Si$_2$, the order parameter associated with the hidden order state has yet to be established. It is known, however that the hidden order can be suppressed with pressure and high magnetic fields, which results in the development of antiferromagnetism, and the realization of a polarized state respectively. Focused Ion Beam lithography (FIB) of URu$_2$Si$_2$ has enabled high magnetic field observation of quantum oscillations in the resistance, indicating the preservation of sample quality to micron scale structures. These recent advances in FIB lithography have enabled the application of unprecedented electric fields while minimizing the effects of Joule heating in highly conductive metals at cryogenic temperatures. To this end, we have been able to create the necessary sample geometry to study the effect of an electric field upon hidden order in magnetic fields up to 15 T. Preliminary results suggest that above a characteristic threshold electric field, hidden order is suppressed revealing a state with similar magnetoresistive properties to the Kondo lattice in the absence of hidden order. [Preview Abstract] |
Tuesday, March 14, 2017 11:39AM - 11:51AM |
F20.00003: Metamagnetism in the electron-doped chemical substitution series URu$_{\mathrm{2}}$Si$_{\mathrm{2-}}_{x}$P$_{x}_{\mathrm{.}}$ Mark Wartenbe, Andrew Gallagher, Kuan-Wen Chen, Ross McDonald, Greg Boebinger, Ryan Baumbach The heavy fermion intermetallic URu$_{\mathrm{2}}$Si$_{\mathrm{2}}$ exhibits a rich variety of phenomena, including a transition into an unknown broken symmetry state (hidden-order) below the temperature $T_{\mathrm{0}} \quad =$ 17.5 K, deviations from Fermi liquid behavior, and unconventional superconductivity below $T_{\mathrm{c}} \quad =$ 1.4 K. The substitution series URu$_{\mathrm{2}}$Si$_{\mathrm{2-}}_{x}$P$_{x}$ was recently synthesized for the first time, where Si $\to $ P substitution simultaneously induces a small chemical pressure and causes electronic tuning, resulting in a $T-x$ phase diagram that includes hidden order (x \textless 0.03), a no-order Kondo lattice (0.03 \textless $x $\textless 0.26), and antiferromagnetism (0.26 \textless $x $\textless 0.5). We report magnetoresistance and magnetization studies in pulsed magnetic fields up to $H =$ 65 T that reveal breakdown of the Kondo lattice and several high field ordered states, which vary with $x$. We discuss these results in terms of their relationship to the suppression of hidden order towards zero temperature and the breakdown of the Kondo lattice in high magnetic fields, and compare related metamagnetic correlated electron materials. [Preview Abstract] |
Tuesday, March 14, 2017 11:51AM - 12:03PM |
F20.00004: Magnetic Correlations in URu$_2$Si$_2$ under Chemical and Hydrostatic Pressure Travis Williams, Adam Aczel, Collin Broholm, William Buyers, Juscelino Leao, Graeme Luke, Jose Rodriguez-Riviera, Matthew Stone, Murray Wilson, Zahra Yamani URu$_2$Si$_2$ has been an intense area of study for the last 30 years due to a mysterious “hidden order” phase that appears below T$_0$ = 17.5 K. The hidden order phase has been shown to be extremely sensitive to perturbations, being destroyed quickly by the application of a magnetic field, hydrostatic or uniaxial pressure, and chemical doping. While attempting to understand the properties of URu$_2$Si$_2$, neutron scattering has found spin correlations that are intimately related to this hidden order phase and which are also suppressed with these perturbations. Here, I will outline some recent neutron scattering work to study these correlations in two exceptional cases where the hidden order phase is enhanced: hydrostatic pressure and chemical pressure using Fe- and Os-doping. In both of these cases, T$_0$ increases before an antiferromagnetic phase emerges. By performing a careful analysis of the neutron data, we show that these two phases are much more related than had been previously appreciated. This implies that the hidden order is likely compatible with an antiferromagnetic ground state, placing constraints on the nature of the missing order parameter. [Preview Abstract] |
Tuesday, March 14, 2017 12:03PM - 12:15PM |
F20.00005: Optical PumpProbe Study of URu$_{2-x}$Fe$_{x}$Si$_{2}$ Single Crystals Peter Kissin, Verner K. Thorsm$\O$lle, Sheng Ran, M. Brian Maple, Richard D. Averitt We study ultrafast quasiparticle relaxation dynamics near the Fermi Energy $E_{F}$ in URu$_{2-x}$Fe$_{x}$Si$_{2}$ single crystals using optical pump probe spectroscopy. URu$_{2-x}$Fe$_{x}$Si$_{2}$ is a heavy fermion compound that undergoes a low temperature first order phase transition between an enigmatic Hidden Order (HO) phase and a Large Moment Antiferromagnetic (LMAFM) phase with increasing Fe concentration, mimicking the effects of hydrostatic pressure. The quasiparticle relaxation dynamics depend strongly on temperature and excitation density, highlighting a marked sensitivity to gaps in the density of states. In agreement with previous measurements , a clear dependence of the dynamics on the hybridization gap and the HO gap is observed. Additionally, the quasiparticle dynamics evolve as the LMAFM phase is approached with Fe substitution. Furthermore, the onset of gapinfluenced dynamics occurs above the bulk transition temperatures for crystals on both sides of the HO/LMAFM phase boundary. In this presentation, we compare our findings to other experiments that exhibit HO/LMAFM physics above the transition temperature and provide a preliminary interpretation of our data. [Preview Abstract] |
Tuesday, March 14, 2017 12:15PM - 12:27PM |
F20.00006: Enhancement of hidden order and antiferromagnetism in Fe and Os substituted URu$_{\mathrm{2}}$Si$_{\mathrm{2}}$ under pressure. Christian Wolowiec, Noravee Kanchanavatee, Kevin Huang, Sheng Ran, M. Brian Maple We present electrical resistivity measurements made under pressure for the Fe and Os substituted URu$_{\mathrm{2}}$Si$_{\mathrm{2}}$. The parent compound URu$_{\mathrm{2}}$Si$_{\mathrm{2}}$ exhibits a hidden order (HO) phase below $T_{\mathrm{0}} \quad =$ 17.5 K at ambient pressure. A phase transition from HO to a large moment antiferromagnetic (LMAFM) phase is induced by applying pressure $P$ or by substituting Fe or Os for Ru ions. While the substitution of smaller Fe ions reduces the unit cell volume thus creating a positive chemical pressure $P_{\mathrm{ch}}$, the substitution of larger Os ions results in a negative $P_{\mathrm{ch}}$. As Fe concentration ($x)$ is increased, the critical pressure $P_{\mathrm{c}}$ forcing the HO to LMAFM phase transition is reduced from 1.4 GPa at $x \quad =$ 0 to 0 GPa at $x \quad =$ 0.15. By converting $x$ to $P_{\mathrm{ch}}(x)$, we found that $P_{\mathrm{ch}}(x) \quad + \quad P_{\mathrm{c}} \quad \approx $ 1.5 GPa at the phase transition. These results suggest that $P_{\mathrm{ch\thinspace }}$behaves like external $P $in inducing the HO $\to $ LMAFM phase transition. However, we also found that as the Os concentration ($y)$ is increased, a smaller $P_{\mathrm{c}}$ is required to induce the HO $\to $ LMAFM phase transition: $P_{\mathrm{c}} \quad \sim $ 1.4 GPa at $y \quad =$ 0 reduces to $P_{\mathrm{c}} \quad \sim $ 0 GPa at $y \quad =$ 0.065. This is contrary to what one would expect from a negative $P_{\mathrm{ch}}$ effect. Hence, the Os substitution study suggests that $P_{\mathrm{ch}}$ is not solely responsible for inducing the LMAFM phase. [Preview Abstract] |
Tuesday, March 14, 2017 12:27PM - 12:39PM |
F20.00007: Phase diagram of URu2-xFexSi2 under high magnetic field. S. Ran, I. Jeon, N. Kanchanavatee, K. Huang, M. B. Maple, A. Gallagher, K. Chen, D. Graf, R. Baumbach, J. Singleton The search for the order parameter of the hidden order (HO) phase in URu$_{\mathrm{2}}$Si$_{\mathrm{2}}$ has attracted an enormous amount of attention for the past three decades. Measurements on URu$_{\mathrm{2}}$Si$_{\mathrm{2}}$ in high magnetic fields up to 45\textasciitilde T reveal that URu$_{\mathrm{2}}$Si$_{\mathrm{2}}$ displays behavior that is consistent with quantum criticality at a field near 35\textasciitilde T, where a cascade of novel quantum phases was found at and around the quantum critical point, suggesting the existence of competing order parameters. Experiments at high pressure reveal that a first order transition from the HO phase to a large moment antiferromagnetic (LMAFM) phase occurs under pressure at a critical pressure P$_{\mathrm{c}}$. We have recently demonstrated that tuning URu$_{\mathrm{2}}$Si$_{\mathrm{2}}$ by substitution of Fe for Ru offers an opportunity to study the HO and LMAFM phases at atmospheric pressure. In this study, we performed transport measurements in high magnetic field on URu$_{\mathrm{2-x}}$Fe$_{\mathrm{x}}$Si$_{\mathrm{2}}$ single crystals for various values of x and established the phase diagrams of URu$_{\mathrm{2-x}}$Fe$_{\mathrm{x}}$Si$_{\mathrm{2}}$ under high magnetic field. [Preview Abstract] |
Tuesday, March 14, 2017 12:39PM - 12:51PM |
F20.00008: Thermodynamic Measurement of Angular Anisotropy at the Hidden Order Transition of URu$_{\mathrm{2}}$Si$_{\mathrm{2}}$ Jennifer Trinh, Ekkes Bruck, Theo Siegrist, Rebecca Flint, Premala Chandra, Piers Coleman, Arthur Ramirez The heavy fermion compound URu$_{\mathrm{2}}$Si$_{\mathrm{2}}$ continues to attract great interest due to the unidentified hidden order it develops below 17.5 K. The unique Ising character of the spin fluctuations and low-temperature quasiparticles is well established. We present detailed measurements of the angular anisotropy of the nonlinear magnetization that reveal a $\cos^{4}\theta $ Ising anisotropy both at and above the ordering transition. With Landau theory, we show this implies a strongly Ising character of the itinerant hidden order parameter. [Preview Abstract] |
Tuesday, March 14, 2017 12:51PM - 1:03PM |
F20.00009: Identifying strongly correlated elements of a moderately correlated wavefunction in URu2Si2 with resonant inelastic X-ray scattering L. Andrew Wray, Haowei He, Lin Miao, Jonathan Denlinger, Yi-De Chuang, Wanli Yang, Nicholas Butch, Brian Maple, Alexander Gray, Herman Dürr The RIXS technique is best known for significant breakthroughs in the investigation of strongly correlated materials such as cuprates. However, the rapid advancement of RIXS spectrographs has made it increasingly attractive to apply the technique to a broad range of quantum materials outside of this comfort zone. This talk will review lessons learned from our recent measurements on material systems that feature a balance of correlated and itinerant physics, focusing on the hidden order compound URu2Si2, and touching on VO2 and Prussian blue analogue battery electrodes. RIXS spectra are found to reveal essential features defining low energy degrees of freedom in these moderately correlated wavefunctions. In the case of URu2Si2, we show that a principal energy gap defining strong correlations is fragile, and can be melted via modest chemical doping. [Preview Abstract] |
Tuesday, March 14, 2017 1:03PM - 1:15PM |
F20.00010: Angle dependant NMR spectral studies of URu2Si2 Matthew Lawson, Blaine Bush, Kent Shirer, Nicholas Curro We have measured nuclear magnetic resonance spectra as a function of angle and temperature in isotopically enriched URu$_2$Si$_2$. The statistical moments of the spectra are reported as a function of temperature and angle. A strong enhancement of the third moment near the onset of hidden order is observed. [Preview Abstract] |
Tuesday, March 14, 2017 1:15PM - 1:27PM |
F20.00011: URu$_{2-x}$Fe$_x$Si$_2$: magnetic excitations in hidden order and antiferromagnetic phases Nicholas Butch, Sheng Ran, Inho Jeon, Noravee Kanchanavatee, Kevin Huang, Alexander Breindel, Brian Maple, Ryan Stillwell, Yang Zhao, Leland Harriger, Jeffrey Lynn The substitution of Fe for Ru in the heavy fermion compound URu$_2$Si$_2$ drives a transition from Hidden Order (HO) to long-range antiferromagnetic order (AFM) at roughly 5$\%$ Fe. The resulting phase diagram is analogous to that under applied pressure. Using inelastic neutron scattering, we have studied the magnetic excitations in both the HO and AFM phases as a function of Fe concentration. The strong interband scattering that sits at the Brillouin zone edges persists across the HO/AFM boundary, although the energy gap grows. However, the excitations centered on the AFM zone center, which are prominent in the HO phase, disappear in the AFM phase. Implications of these results will be discussed. PRB 94, 201102(R) (2016) [Preview Abstract] |
Tuesday, March 14, 2017 1:27PM - 1:39PM |
F20.00012: Quantum critical scaling in the disordered itinerant ferromagnet UCo$_{1-x}$Fe$_x$Ge Marc Janoschek, Kevin Huang, Serena Eley, Priscilla F. S. Rosa, Leonardo Civale, Eric D. Bauer, Ryan E. Baumbach, M. Brian Maple Belitz-Kirkpatrick-Vojta (BKV) theory shows in excellent agreement with experiment that ferromagnetic quantum phase transitions (QPTs) in clean metals are generally first-order due to the coupling of the magnetization to electronic soft modes, in contrast to the classical analogue that is an archetypical second-order phase transition. For disordered metals BKV theory predicts that the second order nature of the QPT is restored because the electronic soft modes change their nature from ballistic to diffusive. Our low-temperature magnetization study identifies the ferromagnetic QPT in the disordered metal UCo$_{1-x}$Fe$_x$Ge as the first clear example that exhibits the associated critical exponents predicted by BKV theory. [Preview Abstract] |
Tuesday, March 14, 2017 1:39PM - 1:51PM |
F20.00013: Hybridization gap and dual nature of the heavy-fermion compound UPd$_{2}$Al$_{3}$ Wan Kyu Park, Narendra Jaggi, Omar Mehio, Matthew Dwyer, Laura Greene, Ryan Baumbach, Paul Tobash, Eric Bauer, Joe Thompson We present results from point-contact spectroscopy in the non-superconducting state of UPd$_{2}$Al$_{3}$, a heavy-fermion antiferromagnetic superconductor [1]. Spectroscopic signatures are clearly observed including the distinct asymmetric double-peak structure arising from a hybridization gap opening with the formation of a coherent heavy Fermi liquid. While the hybridization gap is extrapolated to remain finite up to $\sim $28 K, close to the temperature around which the magnetic susceptibility forms a broad peak, the conductance enhancement vanishes at $\sim $18 K, slightly above the antiferromagnetic transition temperature. Our analysis suggests that the conductance enhancement weakens rapidly as the $T_{N}$ is crossed from below because the junction is tuned away from the ballistic regime due to increased scattering off magnons associated with the localized U 5$f$ electrons. This shows that while the hybridization gap opening is not directly associated with the antiferromagnetic ordering, its visibility is greatly affected by the temperature-dependent magnetic excitations. Our results not only support a 5$f$ dual nature scenario proposed for understanding properties of this compound but also shed new light on the interplay between the itinerant and localized electrons. [1] N. Jaggi \textit{et al}., arXiv:1610.08601. [Preview Abstract] |
Tuesday, March 14, 2017 1:51PM - 2:03PM |
F20.00014: Signatures of inelastic tunnelling in a uranium-based heavy fermion unconventional superconductor Matthew Neat, Ana Maldonado, J.-Ph. Reid, Andrew Huxley, Peter Wahl Scanning tunnelling microscopy and spectroscopy of uranium-based heavy fermion materials has enabled imaging of the heavy fermion bands as well as spectroscopic insight into the many body effects [1,2]. Here, we use low temperature scanning tunnelling microscopy/spectroscopy (STM/STS) on an unconventional uranium-based heavy fermion superconductor down to ~20 mK and in magnetic fields up to 10 T [3]. Spectroscopic measurements reveal strong signatures of inelastic tunnelling, consistent with phonons and excitations seen in optical measurements such as Raman scattering. I also discuss quasiparticle interference of the heavy electron bands. [1] Imaging the Fano lattice to ‘hidden order’ transition in URu$_{2}$Si$_{2}$, Schmidt et al, Nature, 2010. [2] Visualising the formation of the Kondo lattice and the hidden order in in URu$_{2}$Si$_{2}$, Pegor Aynajian and Ali Yazdani et al, PNAS, 2010. [3] Construction and performance of a dilution-refrigerator based spectroscopic-imaging scanning tunnelling microscope, U. R. Singh, Review of Scientific Instruments, 2013. [Preview Abstract] |
Tuesday, March 14, 2017 2:03PM - 2:15PM |
F20.00015: Hastatic order in the two-channel Kondo-Heisenberg model Guanghua Zhang, Rebecca Flint Understanding Kondo physics in materials with non-Kramers doublets requires understanding the two channel Kondo effect, as valence fluctuations are from a non-Kramers doublet ground state to an excited Kramers doublet. Here, the development of a heavy Fermi liquid requires a channel symmetry breaking hybridization. This order, which breaks both single and double time-reversal symmetry was recently introduced as hastatic order. Here we employ an SU(N) fermionic mean-field treatment of the two-channel Kondo-Heisenberg model on a square lattice to explore properties of hastatic order and particularly the competition between the hastatic order and magnetism, as embodied by a spin liquid phase in our model. For simplicity, only a momentum independent hybrization between the non-Kramers $f^2$ states and conduction electrons is considered. Upon varying the RKKY coupling and conduction electron density, we find both uniform and staggered$[\mathbf{Q}=(\pi,\pi)]$ hastatic order, in addition to the spin liquid phase, with metal-insulator transitions, including Lifshitz transitions inside the staggered phase. As the band degeneracy of the conduction electron bands is broken, the uniform hastatic order is partially suppressed compared to the staggered phase. [Preview Abstract] |
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