Article
Physics, Multidisciplinary
J. Knapp, L. Levitin, J. Nyeki, A. F. Ho, B. Cowan, J. Saunders, M. Brando, C. Geibel, K. Kliemt, C. Krellner
Summary: The nature of the antiferromagnetic order, quantum criticality, and superconductivity in YbRh2Si2 remain unknown. We measured the heat capacity over a wide temperature range using current sensing noise thermometry and observed a sharp anomaly at 1.5 mK, which is identified as an electronuclear transition into a state with spatially modulated electronic magnetic order. Magnetic field measurements show the eventual suppression of this order, demonstrating the coexistence of a large moment antiferromagnet with possible superconductivity.
PHYSICAL REVIEW LETTERS
(2023)
Article
Multidisciplinary Sciences
Jiangfan Wang, Yung-Yeh Chang, Chung-Hou Chung
Summary: This article investigates the microscopic origin and properties of the strange metal phase and proposes a mechanism to explain its emergence. By studying the Kondo-Heisenberg lattice model, it is found that the strange metal phase manifests as a fluctuating critical fermionic spin-liquid metal and exhibits characteristics of quantum criticality.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2022)
Article
Materials Science, Multidisciplinary
Yuan Fang, Zhongzheng Wu, Guowei Yang, Yuwei Zhang, Weifan Zhu, Yi Wu, Chunyu Guo, Yuke Li, Huiqiu Yuan, Jian-Xin Zhu, Yang Liu, Chao Cao
Summary: The surface electronic structure of the topological Kondo semimetal YbPtBi is investigated using theoretical calculations and experimental measurements. The results reveal a reconstruction of the surface electronic structure due to the valence transition of the lanthanide element, leading to different behaviors at the Yb-terminated and Bi-terminated surfaces.
Article
Physics, Multidisciplinary
Yasuhiro Tada
Summary: We investigate the orbital diamagnetism at zero temperature in (2 + 1)-dimensional Dirac fermions with a short-range interaction that undergoes a quantum phase transition to a charge density wave (CDW) phase. By introducing orbital magnetic fields into spinless Dirac fermions on the pi-flux square lattice and utilizing the infinite density matrix renormalization group, we observe that diamagnetism is preserved in the Dirac semimetal regime and gradually suppressed in the CDW regime. Near the quantum critical point of the CDW phase transition, we identify a scaling behavior of the diamagnetism characteristic of the chiral Ising universality class. Additionally, the scaling analysis suggests that the robust orbital diamagnetism at weak magnetic fields in a Dirac semimetal regime holds not only in our model but also in other interacting Dirac fermion systems as long as the scaling regions are sufficiently wide. This scaling behavior can also be regarded as a quantum, magnetic equivalent of the critical Casimir effect, which has been extensively studied for classical phase transitions.
NEW JOURNAL OF PHYSICS
(2022)
Article
Physics, Multidisciplinary
Bjorn Sbierski, Elizabeth J. Dresselhaus, Joel E. Moore, Ilya A. Gruzberg
Summary: The study presents extensive numerical results on the phase diagram and criticality of 2D DDF in the unitary class, revealing a critical line at m = 0 with an energy-dependent localization length exponent. The results challenge conjectured relations between different IQHT models.
PHYSICAL REVIEW LETTERS
(2021)
Article
Multidisciplinary Sciences
Wataru Higemoto, Makoto Yokoyama, Takashi U. Ito, Taiga Suzuki, Stephane Raymond, Youichi Yanase
Summary: Experimental results in the compound CeCo(In1-xZnx)5 show that the magnitude of the magnetic moment decreases and eventually vanishes with decreasing impurity concentration in the coexistence region of superconductivity and magnetic ordering, indicating the presence of a second-order phase transition and a quantum critical point.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2022)
Article
Chemistry, Multidisciplinary
Peter E. Siegfried, Hari Bhandari, Jeanie Qi, Rojila Ghimire, Jayadeep Joshi, Zachary T. Messegee, Willie B. Beeson, Kai Liu, Madhav Prasad Ghimire, Yanliu Dang, Huairuo Zhang, Albert V. Davydov, Xiaoyan Tan, Patrick M. Vora, Igor I. Mazin, Nirmal J. Ghimire
Summary: By utilizing ab initio calculations and measurements of magnetic, thermal, and transport properties, it is demonstrated that orthorhombic CoTe2 is near ferromagnetism, which is suppressed by spin fluctuations. Calculations and transport measurements reveal the presence of nodal Dirac lines, making it a rare combination of proximity to quantum criticality and Dirac topology.
ADVANCED MATERIALS
(2023)
Article
Multidisciplinary Sciences
T. Yokoi, S. Ma, Y. Kasahara, S. Kasahara, T. Shibauchi, N. Kurita, H. Tanaka, J. Nasu, Y. Motome, C. Hickey, S. Trebst, Y. Matsuda
Summary: Recent reports have shown the presence of half-integer thermal quantum Hall conductance in the two-dimensional honeycomb material alpha-RuCl3, even in magnetic fields without out-of-plane components. The measured field-angular variation of the quantized thermal Hall conductance in alpha-RuCl3 has the same sign structure as the topological Chern number of the pure Kitaev spin liquid, indicating that the non-Abelian topological order persists in the presence of non-Kitaev interactions.
Article
Physics, Multidisciplinary
Alexander Steppke, Sandra Hamann, Markus Koenig, Andrew P. Mackenzie, Kristin Kliemt, Cornelius Krellner, Marvin Kopp, Martin Lonsky, Jens Mueller, Lev Levitin, John Saunders, Manuel Brando
Summary: Microstructuring techniques enable high-resolution electrical resistivity measurement in highly conductive materials at ultra-low temperatures, increasing signal-to-noise ratios and without adverse effects to sample quality. This study demonstrates microstructuring as a powerful tool for investigating the resistance and noise spectrum of highly conductive correlated metals over wide temperature ranges.
NEW JOURNAL OF PHYSICS
(2022)
Article
Multidisciplinary Sciences
Mariam Kavai, Joel Friedman, Kyle Sherman, Mingda Gong, Ioannis Giannakis, Samad Hajinazar, Haoyu Hu, Sarah E. Grefe, Justin Leshen, Qiu Yang, Satoru Nakatsuji, Aleksey N. Kolmogorov, Qimiao Si, Michael Lawler, Pegor Aynajian
Summary: The research reveals an electronic phase separation in single crystalline Pr2Ir2O7, with well-defined Kondo resonances interweaved with a non-magnetic metallic phase with Kondo-destruction.
NATURE COMMUNICATIONS
(2021)
Article
Multidisciplinary Sciences
Carolina A. Marques, Luke C. Rhodes, Izidor Benedicic, Masahiro Naritsuka, Aaron B. Naden, Zhiwei Li, Alexander C. Komarek, Andrew P. Mackenzie, Peter Wahl
Summary: The phenomenon and radical changes observed in material properties during a quantum phase transition have attracted significant attention in condensed matter research in recent decades. Strong electronic correlations give rise to exotic electronic ground states, such as magnetic order, nematicity, and unconventional superconductivity. A detailed understanding of the electronic structure near the Fermi energy is necessary to provide a microscopic model for these phenomena and achieve a complete understanding of the physics of the quantum critical point.
Article
Multidisciplinary Sciences
S. K. Kanungo, J. D. Whalen, Y. Lu, M. Yuan, S. Dasgupta, F. B. Dunning, K. R. A. Hazzard, T. C. Killian
Summary: This study demonstrates the creation of a synthetic dimension using Rydberg atoms, which supports topological edge states. By engineering the tunneling amplitudes and on-site potentials, the authors successfully realize the one-dimensional Su-Schrieffer-Heeger Hamiltonian, a paradigmatic model of topological matter. The probed band structure reveals symmetry-protected topological edge states at zero energy.
NATURE COMMUNICATIONS
(2022)
Article
Multidisciplinary Sciences
An Wang, Feng Du, Yongjun Zhang, David Graf, Bin Shen, Ye Chen, Yang Liu, Michael Smidman, Chao Cao, Frank Steglich, Huiqiu Yuan
Summary: Ferromagnetic quantum criticality was observed in CeRh6Ge4 under moderate hydrostatic pressure, supported by quantum oscillation measurements. The study found that Ce 4f electrons remain localized and do not contribute to the Fermi surface, suggesting localized ferromagnetism as a key factor for the occurrence of a ferromagnetic quantum critical point in CeRh6Ge4.
Article
Materials Science, Multidisciplinary
Lucas Squillante, Luciano S. Ricco, Aniekan Magnus Ukpong, Roberto E. Lagos-Monaco, Antonio C. Seridonio, Mariano de Souza
Summary: This article proposes a quantum analog to the Gruneisen ratio Gamma, which computes entanglement as a function of a tuning parameter lambda and investigates quantum critical points. The authors demonstrate that quantum phase transitions only occur when the ground-state energy depends nonlinearly on lambda. Furthermore, the breakdown of the Hellmann-Feynman theorem at any quantum critical point is shown.
Article
Physics, Multidisciplinary
Jan Behrends, Benjamin Beri
Summary: This paper presents the construction of fermionic all-to-all Floquet quantum circuits to simulate the dynamics of the SYK model. These circuits can be built using local ingredients in Majorana devices, allowing for the reconciliation of all-to-all interactions with the topological protection of Majorana zero modes, which is lacking in existing analog SYK simulation proposals. The paper also describes how dynamical correlation functions, including out-of-time-ordered ones, can be measured in such analog-digital implementations using the anticipated capabilities of Majorana devices.
PHYSICAL REVIEW LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Georg Poelchen, Igor P. Rusinov, Susanne Schulz, Monika Guttler, Max Mende, Alexander Generalov, Dmitry Yu Usachov, Steffen Danzenbaecher, Johannes Hellwig, Marius Peters, Kristin Kliemt, Yuri Kucherenko, Victor N. Antonov, Clemens Laubschat, Evgueni Chulkov, Arthur Ernst, Kurt Kummer, Cornelius Krellner, Denis V. Vyalikh
Summary: The temperature scales at the surfaces of strongly correlated materials have attracted research attention. A two-dimensional Ce Kondo lattice is observed below the surface of the antiferromagnet CeCo2P2. The Ce 4f states become partially occupied and spin-polarized near the surface, interacting strongly with surface states. This study demonstrates the rich and diverse f-driven properties at the surface of materials without f-physics in the bulk.
Article
Physics, Multidisciplinary
J. Knapp, L. Levitin, J. Nyeki, A. F. Ho, B. Cowan, J. Saunders, M. Brando, C. Geibel, K. Kliemt, C. Krellner
Summary: The nature of the antiferromagnetic order, quantum criticality, and superconductivity in YbRh2Si2 remain unknown. We measured the heat capacity over a wide temperature range using current sensing noise thermometry and observed a sharp anomaly at 1.5 mK, which is identified as an electronuclear transition into a state with spatially modulated electronic magnetic order. Magnetic field measurements show the eventual suppression of this order, demonstrating the coexistence of a large moment antiferromagnet with possible superconductivity.
PHYSICAL REVIEW LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Marius Peters, Kristin Kliemt, Michelle Ocker, Bernd Wolf, Pascal Puphal, Matthieu Le Tacon, Michael Merz, Michael Lang, Cornelius Krellner
Summary: EuPd2Si2 undergoes a temperature-induced valence crossover at T-V' approximately 160 K. Single crystals of EuPd2(Si1-xGex)(2) with substitution levels x <= 0.15 were successfully grown using the Czochralski method. The determination of germanium content shows that only half of the nominal concentration is incorporated into the crystal structure. Thermodynamic measurements reveal that T-V' is strongly suppressed for small substitution levels and antiferromagnetic order emerges for x >= 0.10.
PHYSICAL REVIEW MATERIALS
(2023)
Article
Physics, Multidisciplinary
Chia-Jung Yang, Kristin Kliemt, Cornelius Krellner, Johann Kroha, Manfred Fiebig, Shovon Pal
Summary: Using terahertz time-domain spectroscopy, evidence for fermionic critical slowing down in YbRh2Si2 close to a quantum phase transition is found. The heavy-fermion quasiparticles in the heavy-Fermi-liquid state break down at the transition, as indicated by measurements of critical slowing down. This breakdown of heavy-fermion quasiparticles near the quantum phase transition could classify this system among a wider family of fermionic quantum phase transitions that is yet to be fully explored.
Article
Multidisciplinary Sciences
G. Poelchen, J. Hellwig, M. Peters, D. Yu. Usachov, K. Kliemt, C. Laubschat, P. M. Echenique, E. V. Chulkov, C. Krellner, S. S. P. Parkin, D. V. Vyalikh, A. Ernst, K. Kummer
Summary: The metallic antiferromagnet CeCo2P2 exhibits long-lived spin-waves at terahertz frequencies, suggesting the potential use of metallic antiferromagnets for spin-wave information processing.
NATURE COMMUNICATIONS
(2023)
Article
Physics, Applied
U. Arjun, K. M. Ranjith, A. Jesche, F. Hirschberger, D. D. Sarma, P. Gegenwart
Summary: Attaining millikelvin temperatures is crucial for studying quantum phenomena and operating quantum devices. Adiabatic demagnetization refrigeration (ADR) is a sustainable and effective alternative to expensive cooling methods. We present the synthesis and characterization of two UHV-compatible candidate materials, NaYbP2O7 and KYbP2O7, and report their low-temperature magnetization and specific heat measurements. Under similar conditions, the ADR of sintered pellets with Ag powder admixture achieved base temperatures of 45 mK (55 min) for NaYbP2O7 and 37 mK (35 min) for KYbP2O7, which are slightly better than KBaYb(BO3)2 (45 mK and 40 min).
PHYSICAL REVIEW APPLIED
(2023)
Article
Materials Science, Multidisciplinary
Bernd Wolf, Theresa Lundbeck, Jan Zimmermann, Marius Peters, Kristin Kliemt, Cornelius Krellner, Michael Lang
Summary: In this study, the magnetic susceptibility of high-quality single crystals of EuPd2(Si1-xGex)2 with Ge concentrations 0 ≤ x ≤ 0.105 was measured under varying hydrostatic pressure (He-gas) of 0 to 0.5 GPa. The results reveal that the magnetic response changes drastically from valence-crossover behavior to long-range antiferromagnetic order as the Ge concentration increases to x = 0.105. The valence-crossover temperature shows a strong pressure dependence, while the pressure dependence of the antiferromagnetic order is small.
Article
Materials Science, Multidisciplinary
Mai Ye, Mark Joachim Graf von Westarp, Sofia-Michaela Souliou, Marius Peters, Robert Moeller, Kristin Kliemt, Michael Merz, Rolf Heid, Cornelius Krellner, Matthieu Le Tacon
Summary: The valence crossover and strong electron-phonon coupling of EuPd2Si2 were studied using polarization-resolved Raman spectroscopy. The fully symmetric phonon mode exhibited a strongly asymmetric line shape at low temperature, indicating Fano-type interaction with a continuum of electron-hole excitations. Additionally, anomalies in the frequency and linewidth of the phonon modes were observed across the valence-crossover temperature, suggesting coupling between valence fluctuations and lattice vibration. Density-functional-theory calculations were used to evaluate the relative contribution of structural change and valence change to the phonon anomalies.
Article
Physics, Multidisciplinary
Rajah P. Nutakki, Richard Roess-Ohlenroth, Dirk Volkmer, Anton Jesche, Hans-Albrecht Krug von Nidda, Alexander A. Tsirlin, Philipp Gegenwart, Lode Pollet, Ludovic D. C. Jaubert
Summary: Geometric frustration prevents magnetic systems from ordering, allowing for unconventional phases of matter. Using molecular design, we have created a material [Mn(II)(ta)2] that exhibits a centered pyrochlore lattice of Mn spins, which shows features of a classical spin liquid. Despite having a Curie-Weiss temperature of -21 K, the material only orders at 430 mK, making it a highly frustrated magnet.
PHYSICAL REVIEW RESEARCH
(2023)
Article
Materials Science, Multidisciplinary
A. Jesche, N. Winterhalter-Stocker, F. Hirschberger, A. Bellon, S. Bachus, Y. Tokiwa, A. A. Tsirlin, P. Gegenwart
Summary: Crystal structure, thermodynamic properties, and ADR effect of the spin-72 triangular antiferromagnet KBaGd(BO3)2 are investigated. The compound shows magnetic order below TN = 263 mK and achieves ADR temperatures as low as Tmin = 122 mK, along with improved entropy storage capacity and hold time compared to the spin-21 Yb3+ analog. The balanced interplay of exchange and dipolar couplings, combined with structural randomness and geometrical frustration, is believed to contribute to the enhanced cooling effect.
Article
Materials Science, Multidisciplinary
Young -Joon Song, Susanne Schulz, Kristin Kliemt, Cornelius Krellner, Roser Valenti
Summary: We investigate the mechanism of the valence transition from nearly divalent to nearly trivalent Eu in tetragonal EuPd2Si2 under volume compression by ab initio DFT calculations. Enhanced c-f hybridization and electronic charge redistribution are observed near the valence transition, which is closely related to the volume reduction and the delicate balance between various factors. Comparison with photoemission data confirms the mixed-valent properties of EuPd2Si2 and highlights the limitations of DFT in describing valence transitions.
Article
Physics, Multidisciplinary
A. Woerl, M. Garst, Y. Yamane, S. Bachus, T. Onimaru, P. Gegenwart
Summary: This study reports on the low-temperature thermal expansion and magnetostriction properties of the single-impurity quadrupolar Kondo candidate Y1-xPrxIr2Zn20. It reveals a unique temperature and magnetic field dependence, as well as a singular behavior in zero magnetic field, which is possibly induced by elastic anharmonicities or static strain disorder.
PHYSICAL REVIEW RESEARCH
(2022)
Article
Materials Science, Multidisciplinary
L. Salamakha, O. Sologub, A. Riss, H. Michor, H. Mueller, B. Stoeger, G. Giester, P. Rogl, A. Sakai, P. Gegenwart, E. Bauer
Summary: Novel ternary platinum borides YbPt5B2 and LuPt5B2 were synthesized and their crystal structures and electronic properties were investigated. YbPt5B2 exhibits heavy fermion behavior, while LuPt5B2 shows typical metallic behavior.
Article
Materials Science, Multidisciplinary
M. Majumder, R. Gupta, H. Luetkens, R. Khasanov, O. Stockert, P. Gegenwart, V. Fritsch
Summary: CePdAl is a frustrated Kondo lattice with partial long-range order. Under pressure, the long-range order is completely suppressed, and spin-liquid behavior is observed. There is a quantum critical regime between pressure and temperature.
Article
Quantum Science & Technology
Tobias Biesner, Seulki Roh, Aleksandar Razpopov, Jannis Willwater, Stefan Suellow, Ying Li, Katharina M. Zoch, Marisa Medarde, Juergen Nuss, Denis Gorbunov, Yurii Skourski, Andrej Pustogow, Stuart E. Brown, Cornelius Krellner, Roser Valenti, Pascal Puphal, Martin Dressel
Summary: The spin density of states (SDOS) can be accessed over the entire Brillouin zone in the distorted kagome quantum magnet Y-kapellasite through three-center magnon excitations. This provides a new aspect to probe magnetism in matter, relaxing the conventional zone-center constraint of photons.
ADVANCED QUANTUM TECHNOLOGIES
(2022)