Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session K63: Heavy Fermions IRecordings Available
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Sponsoring Units: DCMP Chair: Pei-Chun Ho, Califor. State U, Fresno Room: Hyatt Regency Hotel -Grant Park A |
Tuesday, March 15, 2022 3:00PM - 3:12PM |
K63.00001: High field magnetization anisotropy in cubic CeIn3 single crystal Yu Liu, Esteban A Ghioldi, Neil Harrison, Shannon S Fender, Priscila Rosa, Joe D Thompson, Eric D Bauer, Yusuke Nomura, Ryotaro Arita, Zhentao Wang, Cristian Batista, Filip Ronning Cubic CeIn3 is a heavy fermion material that displays fascinating phenomena including pressure and field-induced quantum criticality, antiferromagnetism, Fermi surface transformations, and unconventional superconductivity. By using a large magnetic field with strength comparable to the crystal field energy scale, CeIn3 shows a non-trivial phase diagram depending on the field orientation from resistivity measurement [1]. To begin to understand the complex interplay of these phenomena, we have derived a minimal low energy Kondo lattice model containing material specific first-principles and spectroscopic input. To validate this model, we have derived the magnetic exchange interaction of the full J = 5/2 multiplet, and computed the anisotropic magnetization versus magnetic field. In this talk, I will discuss magnetization measurements of CeIn3 along the three principle directions [100], [110], and [111] up to 60 T to derive the cubic anisotropy of the exchange interactions. The results reasonably validate our theoretical low energy model that includes the excited crystal field levels. |
Tuesday, March 15, 2022 3:12PM - 3:24PM |
K63.00002: Transport and shot noise measurements in YbRh2Si2 nano wires Liyang Chen, Dale T Lowder, Emine Bakali, Lukas Prochaska, Aaron M Andrews, Silke Paschen, Douglas Natelson The heavy fermion compound YbRh2Si2 exhibits a magnetic field-induced quantum critical point, between an antiferromagnetically ordered phase and a paramagnetic heavy Fermi liquid phase. Although the zero-field magnetic ordering temperature is only 70 mK, quantum critical non-Fermi liquid behavior persists over a broad temperature range, providing a wide parameter space to study the electron correlations in this “strange metal” system. Here we fabricate YbRh2Si2 nanowires using Ar dry etch, with chromium hard masks used to cover the designed pattern and removed by hydrochloric acid. The etched nanowires are examined by measuring magnetoresistance and comparing with those of the unpatterned original film, showing that the patterning does not degrade the material. We measure the shot noise in the nanowires and compared the signal in this non-Fermi liquid system with the shot noise in a conventional metal. We find suppressed shot noise in YbRh2Si2 nanowires, which is less than half of the noise in normal metal wires of comparable dimensions and resistance. We discuss this suppressed noise in the context of electron-electron interactions and the suggested lack of well-defined quasiparticles in strange metals. |
Tuesday, March 15, 2022 3:24PM - 3:36PM |
K63.00003: Quantum Criticality of the Quasi-One-Dimensional Heavy Fermion Material YbFe5P3 Eric D Bauer, Keenan Avers, Tomoya Asaba, Sangyun Lee, Soonbeom Seo, Yu Liu, Ashley Weiland, Sean Thomas, Priscila Rosa, Roman Movshovich, Joe D Thompson, Jon Lawrence, W. P Halperin, Filip Ronning Quantum criticality has been an organizing principle to explain the behavior of many families of quantum materials including the high-temperature cuprate and iron-based superconductors and f-electron heavy fermion compounds. A central, unresolved issue is the role of quantum fluctuation dimensionality on the properties of the system. Most work to date has focused on quantum criticality with two-dimensional (2-D) and three-dimensional (3-D) fluctuations. Strong quantum fluctuations are expected in quasi-1-D materials and have recently been explored in 1-D f-electron materials such as CeRh6Ge4 [1], Yb2Pt2Pb [2], and YbAlO3 [3]. |
Tuesday, March 15, 2022 3:36PM - 3:48PM |
K63.00004: Valence Fluctuations and Othe Correlated Electron Behavior in Yb1-xScxCo2Zn20 Camilla M Moir, Naveen Pouse, Duygu Yazici, Aaron J Friedman, Brian Maple We examine the effect of chemical pressure on YbCo2Zn20 by studying the system Yb1-xScxCo2Zn20 where the smaller, non-magnetic Sc ion has been substituted for Yb. From x-ray powder diffraction measurements of the lattice constant a and magnetization measurements, we find that for low Sc content substitutions, the Yb valence vYb decreases linearly from 3+ at x = 0 to ~ 2.7+ x = 0.3 where vYb stabilizes and follows Vegard’s law for x ≥ 0.3. Resistivity measurements reveal a low-temperature upturn that can be described by a log T-dependence, consistent with the predictions of the single ion Kondo model; however, specific heat measurements cannot be fit by the resonance level model for the Kondo effect. Further analysis of C(T)/T for Yb1-xScxCo2Zn20 reveal signatures consistent with non-Fermi Liquid like behavior which suggests a nearby quantum critical point (QCP). The Yb1-xScxCo2Zn20 system shows a confluence of phenomena typically found in 4f electron systems including crystalline electric field effects, valence fluctuations, the Kondo effect, and heavy fermion behavior. |
Tuesday, March 15, 2022 3:48PM - 4:00PM |
K63.00005: Small-to-large Fermi surface fluctuations in heavy fermion systems I: Dynamical scaling Haoyu Hu, Ang Cai, Lei Chen, Lili Deng, Jedediah H Pixley, Kevin Ingersent, Qimiao Si Studies in heavy fermion systems have led to the notion of Kondo destruction. It characterizes a beyond-Landau quantum critical point, across which the Fermi surface goes from “large” to “small” [1]. An important signature of the Kondo destruction quantum criticality appears in the anomalous dynamical critical properties, as studied in Kondo lattice models by extended dynamical mean-field theory (EDMFT) [1,2], with fractional exponent and E/T scaling [3]. Here we carry out the first cluster-EDMFT analysis of an Anderson lattice model. We show that, for both Ising-anisotropic and SU(2)-symmetric models, the Kondo destruction captures the anomalous dynamical scaling in a robust way [4]. Implications of our results for unconventional superconductivity in these systems [4] will be discussed in the next talk. |
Tuesday, March 15, 2022 4:00PM - 4:12PM |
K63.00006: Small-to-large Fermi surface fluctuations in heavy fermion systems II: Unconventional superconductivity Haoyu Hu, Ang Cai, Lei Chen, Lili Deng, Jedediah H Pixley, Kevin Ingersent, Qimiao Si How unconventional superconductivity develops from quantum critical metals is a central question in strongly correlated systems. In the studies of antiferromagnetic heavy fermion metals, the notion of Kondo destruction quantum critical point, at which a sharp large-to-small Fermi surface reconstruction appears, has been developed [1]. Here, we demonstrate unconventional superconductivity developing from Fermi surface fluctuations in the Anderson lattice model, in the first analysis based on the cluster-EDMFT approach [2]. For both Kondo-destruction and SDWr quantum criticality, we find that the superconducting transition temperature is exceptionally high relative to the effective Fermi temperature, reaching several percent of the bare Kondo temperature scale [3]. Our results provide a natural understanding of the enigmatic superconductivity in a host of heavy-fermion metals. Implications will be discussed for other classes of strongly correlated systems with superconductivity developing from Fermi-surface fluctuations. |
Tuesday, March 15, 2022 4:12PM - 4:24PM |
K63.00007: Small-to-large Fermi surface fluctuations in heavy fermion systems III: Crossover between Kondo destruction and SDWr quantum criticality Lei Chen, Ang Cai, Haoyu Hu, Qimiao Si The notion of Kondo destruction characterizes a beyond-Landau quantum critical point, across which Fermi surface goes from “large” to “small” [1]. Here we show that, even when the quantum transition is of a fluctuating spin-density-wave order (SDW), the upper cutoff of the Landau quantum criticality, $E_cr$, is considerably smaller than the bare Kondo scale ($E_K^0$). The small $E_cr/E_K^0$ ratio captures the dynamical competition between the RKKY and Kondo interactions. We systematically demonstrate this effect in an Anderson lattice model within an EDMFT approach. Accordingly, we propose the notion of SDW$_r$ quantum criticality, in which the associated SDW order comes from renormalized heavy quasiparticle and, accordingly, a substantial dynamical range ($E_cr$, $E_K^0$) exists for Kondo-destruction quantum criticality. We discuss why several quantum critical heavy fermion metals fall into this picture. Our work provides the foundation for the recently advanced theory of heavy-fermion superconductivity [2] presented in the previous talk. |
Tuesday, March 15, 2022 4:24PM - 4:36PM |
K63.00008: Quantum Criticality of Kondo Lattice Model: A Renormalization Group Study via Quantum non-Linear Sigma Model Yiming Wang, Chia-Chuan Liu, Qimiao Si Quantum criticality has attracted considerable interest in many strongly correlated systems. Heavy fermion metals represent a prototype of such systems [1]. Here the interplay between local moments and itinerant electrons introduces novel quantum phase transitions and critical properties and, at the same time, presents a challenge to theoretical understanding. In this work, we approach the problem from the magnetically ordered side and analyze Kondo lattice models in a quantum nonlinear sigma model representation. By treating the local moments and itinerant electrons on an equal footing, we analyze the competition between the Kondo and RKKY couplings using a renormalization group analysis. Our results shed new light on the global phase diagram of the heavy fermion metals [2] and, especially, the behavior of the frustrated Kondo lattice systems [3,4]. |
Tuesday, March 15, 2022 4:36PM - 4:48PM |
K63.00009: Kondo-destruction quantum criticality in the particle-hole asymmetric Bose-Fermi Anderson model Ananth Kandala, Haoyu Hu, Qimiao Si, Kevin Ingersent Critical destruction of the Kondo effect is believed to underlie beyond-Landau quantum criticality in a number of heavy-fermion metals [1]. Insight into the phenomenon can be obtained from Bose-Fermi impurity models, which arise in extended dynamical mean-field descriptions of heavy-fermion quantum criticality [2]. This talk addresses the Bose-Fermi Anderson model with a power-law bosonic bath having an exponent s < 1 and a fermionic band with a density of states that vanishes at the Fermi energy as ρ(ε) ∝ |ε-εF|r with r > 0. We focus on the regime r > ½ in which criticality occurs only away from particle-hole symmetry, using a continuous-time quantum Monte Carlo method for both spin-isotropic and Ising-anisotropic variants of the model, and the numerical renormalization-group method for Ising anisotropy. We examine the nature of the dominant critical fluctuations for different combinations of r and s, finding that the criticality groups into fundamentally different classes. We discuss the difference in our conclusions from those reached on the basis of a double epsilon-expansion approach [3]. |
Tuesday, March 15, 2022 4:48PM - 5:00PM |
K63.00010: Phase diagram of Yb doped CeCoIn5 William Dupuis, Sjoerd Roorda, Andrea Bianchi Inspired by the work of Nakatsuji et al., we explore the temperature-doping phase diagram of Ce1-xYbxCoIn5. In the so-called 115 structure, Yb is a priory divalent and non-magnetic, and as a consequence doping CeCoIn5 with Yb removes a magnetic ion, as well as a charge at the same time. At low levels of Yb substitution, the lattice parameter remains almost unchanged. Our study will show if the Yb doped CeCoIn5 case can be analyzed similar to the case of La doping, where the system can be described by a separation of the Kondo response into a coherent lattice part, and an incoherent single ion contribution. CeCoIn5 is an example of a heavy fermion material that exhibits unconventional superconductivity, which is attributed to Kondo lattice coherence. The crystal also exhibits non-Fermi liquid behaviour due to an antiferromagnetic (AFM) instability near a quantum critical point (QCP). We treat this doping as the tuning parameter of the QCP. Wishing to probe only the magnetic specific heat, we removed all phonon contributions by using LaCoIn5 as the non-magnetic conjugate of the CeCoIn5. This consists of a series of high precision measurements of the specific heat on both compounds. This study aims at providing a better understanding of the superconducting state of Kondo materials in the 115 family exploiting a new tuning parameter. |
Tuesday, March 15, 2022 5:00PM - 5:12PM |
K63.00011: Engineering heavy fermions in twisted graphene multilayers Jose Lado, Aline Ramires Twisted van der Waals materials have been shown to host a variety of tunable electronic structures. Here we put forward twisted graphene multilayers as a platform to emulate heavy fermion physics. In particular, we demonstrate that twisted graphene trilayer hosts extended and localized modes with an electronic structure that can be controlled by interlayer bias. In the presence of interactions, the existence of localized modes leads to the development of local moments, which are Kondo coupled to coexisting extended states. By electrically controlling the effective exchange between local moments, the system can be driven from a magnetic into a heavy fermion regime, passing through a quantum critical point. Our results put forward twisted graphene multilayers as a platform for the realization of strongly correlated heavy fermion physics in a purely carbon-based platform. |
Tuesday, March 15, 2022 5:12PM - 5:24PM |
K63.00012: Anisotropic quantum criticality in CeCoIn5 from ultrafast nanocalorimeter spectroscopy Akash Khansili CeCoIn5 features divergence of quasiparticle mass at very low temperatures which is currently understood as a result of an antiferromagnetic quantum critical point (QCP). NMR measurements show that mass increase is cut off in a finite magnetic field at very low temperatures indicating energy scale competition near the QCP. However, these measurements do not reveal the full spectrum of quantum fluctuations and their angular anisotropy. Additionally, Heat capacity measurements are challenging at these temperatures and magnetic fields because of the strong nuclear Schottky from Indium115. We use novel nanocalorimeter spectroscopy to determine electronic heat capacity and nuclear Schottky in CeCoIn5 at ultralow temperatures. I will discuss the new results and implications for the physics of CeCoIn5. |
Tuesday, March 15, 2022 5:24PM - 5:36PM |
K63.00013: Heavy-fermion quantum criticality via two-stage screening Andreas Gleis, Seung-Sup B Lee, Andreas Weichselbaum, Gabriel Kotliar, Jan Von Delft We address a Kondo breakdown quantum critical point (QCP) in heavy-fermion systems by studying the periodic Anderson model using a two-site cellular dynamical mean-field theory (DMFT) approach. By employing the numerical renormalization group (NRG) to solve the effective impurity model, we are able to dispose of the limitations faced by previous two-site DMFT studies. At zero temperature, we find a Kondo breakdown QCP separating two Fermi-liquid (FL) phases, which differ in their Fermi surface volumes. These FL phases are reached via a two-stage screening process, leading to non-Fermi liquid (NFL) behavior at finite temperatures. In this talk, we will specifically focus on frequency over temperature scaling of the optical conductivity in the NFL region, where we find good qualitative agreement with recent experimental results on YbRh2Si2. |
Tuesday, March 15, 2022 5:36PM - 5:48PM |
K63.00014: Composition of magnetic interactions in the heavy-fermion system CeIn3 Wolfgang J Simeth, Zhentao Wang, David M Fobes, Andrey Podlesnyak, Eric D Bauer, Jakob Lass, Daniel Mazzone, Christof Niedermayer, Yusuke Nomura, Ryotaro Arita, Cristian Batista, Filip Ronning, Marc Janoschek, Esteban A Ghioldi, Nakheon Sung, Jakub Vonka We report high-resolution neutron spectroscopy on the archetypal heavy fermion material CeIn3 that exhibits an antiferromagnetic (AFM) order below TN = 10.1 K. Increasing pressure suppresses the AFM state to zero temperature resulting in a quantum critical point, the critical fluctuations of which are believed to mediate unconventional superconductivity. Previous neutron results with moderate resolution reported a substantial spin gap of about 1 meV, which suggest a substantial magnetic anisotropy, in contrast to the observed bulk properties. Our results unambiguously demonstrate that CeIn3 does not exhibit a spin gap. Instead, we find that the spin waves disperse quasi-vertically up to almost 1 meV. We show that via ab-initio band structure calculations fed into the multi-orbital periodic Anderson model can predict the magnetic excitation spectrum quantitatively. Our results show that this model can be renormalized to a simple Kondo lattice model decorated with short-range super exchange interactions to account for the formation of magnetic order. This microscopically-derived modified Kondo lattice model quantitatively reproduces the low-energy magnetic soft modes in CeIn3, which are key to understanding unconventional superconductivity. |
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