Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session M30: Strongly Correlated Systems, Including Quantum Fluids and Solids X |
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Sponsoring Units: DCMP Chair: Jianhao Zhang, The Pennsylvania State University Room: Room 222/223 |
Wednesday, March 8, 2023 8:00AM - 8:12AM |
M30.00001: Intermediate Valence state in YbB4 revealed by Resonant X-Ray Emission Spectroscopy (RXES) Felix I Frontini, Young-June Kim, Blair W Lebert, Chris Pollock, Beongki Cho, Keunki Cho, Myungsuk Song In crystal systems with competing, incongruous, anti-ferromagnetic exchange interactions, geometric frustration is found and often leads to the suppression of long-range magnetic order. On the other hand, in Yb-based systems where the Kondo interaction between 4f and conduction electrons is dominant, hybridization between these also results in the suppression of magnetic order. When the Kondo interaction is strong enough physical hybridization between the 4f and conduction electrons occurs, resulting in a quantum mechanically degenerate electronic ground-state, a so-called intermediate valence (IV) state. YbB4 is a rare system where both mechanisms are plausible explanations for the lack of magnetic order [1]. YbB4 crystallizes into a tetragonal crystal structure (space group P4/mbm) mapped to the well known geometrically frustrated Shastry-Sutherland Lattice within the ab plane [2]. YbB4 has also been proposed as a Kondo-dominated system residing in the IV regime but has to date lacked direct confirmation of such via spectroscopic means [3,4]. We study the existence of an IV state in YbB4 using RXES at the Yb L(α1) transition and study the temperature dependence of the Yb valence from 12 to 300 K. We confirm that YbB4 exists in an IV state at all temperatures, with the Yb valence increasing from v=2.61±0.01 at 12 K to v=2.67±0.01 at 300 K. |
Wednesday, March 8, 2023 8:12AM - 8:24AM |
M30.00002: A Fractional Chern Insulator in a Multichannel Kondo Lattice Yang Ge, Yashar Komijani Multichannel Kondo lattice brings together strong interaction and channel symmetry selection, to create a fascinating playground for theoretical studies with potential experimental realizations. Previous works have found a wealth of critical phases in a multichannel Kondo impurity or Kondo chain, admitting different patterns of channel symmetry breaking and entanglement. We use the dynamical large-N technique with the Abrikosov fermion representation of spins to study the multichannel Kondo model on a honeycomb lattice. This enables us to access a 2+1D relativistic quantum critical fixed point of spinons and holons, governed by critical exponents that are found analytically with our conformal solution and cross-checked numerically. Next, we break time-reversal symmetry by adding a Haldane mass to the conduction elections. Remarkably, the spin-liquid inherits a gap via a resonantly amplified dispersion which leads to Kondo flux repulsion. The bosonic channel degree of freedom can exhibit both ordered (gapless) and disordered (gapped) phases separated by a quantum critical point. In the gapped phase, we compute the electrical and thermal Hall conductivities, which show deviations from Wiedemann-Franz law and establish a fractional Chern insulator. |
Wednesday, March 8, 2023 8:24AM - 8:36AM |
M30.00003: Measuring entanglement at finite temperatures Cheolhee Han, Yigal Meir, Eran Sela Relating the entanglement of many-body systems at finite temperature to measurable observables is desirable. In this talk, we provide relations between Renyi moments of an entanglement monotone and measurable observables. First we introduce a new entanglement monotone, the number entanglement entropy [1]. It is an entropy change due to an unselective subsystem charge measurement, and is an entanglement monotone for the systems with a conserved charge. Next, we derive finite temperature equilibrium relations between the Renyi moments of the number entanglement entropy and multi-point charge correlation functions. We exemplify these relations in quantum dot systems where the desired charge correlations can be measured via a nearby quantum point contact. Especially, in the multi-channel Kondo effect, we show that the number entanglement entropy and its Renyi moments have the same nontrivial universal temperature dependence at low temperature, which is now accessible using the proposed methods. |
Wednesday, March 8, 2023 8:36AM - 8:48AM |
M30.00004: Microscopic theory of multi-stage Fermi surface reconstruction in heavy fermion systems with quartet multipolar local moments SangEun Han, Daniel J Schultz, Yong Baek Kim Recent experiments on Ce3Pd20(Si,Ge)6 show novel quantum critical behaviors associated with two consecutive quantum phase transitions upon varying the external magnetic field. Interestingly, the derivative of the Hall conductivity shows a discontinuous jump at each phase transition, which was attributed to sequential Fermi surface reconstructions. Motivated by this discovery and previous theory work, we consider a microscopic model of itinerant electrons coupled to the local moments described by a quartet of ground states in a crystal-electric-field (CEF). Such a quartet arises due to two degenerate Kramers doublets of Ce3+ ions in a cubic CEF and supports a large number of dipolar, quadrupolar, and octupolar moments. Specifically, we investigate emergent quantum phase transitions and criticality in a local effective model, the so-called Bose-Fermi Kondo model. This model describes the competition between the Kondo effect with the itinerant electrons and RKKY interaction for all of the 15 symmetry-allowed multipolar moments. Using renormalization group analyses, we demonstrate that a multitude of quantum phase transitions can occur depending on which multipolar moments participate in the Fermi surface formation and which other multipolar moments are decoupled via Kondo destruction. We provide a concrete example of two consecutive quantum phase transitions that involve the quadrupolar and dipolar/octupolar moments at two different stages. Our work provides an illuminating insight as to the importance of local symmetries in understanding multipolar Kondo lattice systems and an outlook for future directions. |
Wednesday, March 8, 2023 8:48AM - 9:00AM |
M30.00005: Quantum criticality in an artificial moire Kondo lattice Zhongdong Han, Yiyu Xia, Kenji Watanabe, Takashi Taniguchi, Jie Shan, Kin Fai Mak We artificially construct a two-dimensional Kondo lattice by combining transition metal dichalcogenide (TMD) moire superlattices with an angle-misaligned monolayer. At half band filling of the moire lattice, strong on-site Coulomb repulsion localizes electrons to form a triangular lattice, which provides local spin moments for the Kondo lattice. Angle-misaligned TMD monolayer hosts itinerate electrons coupled with the local moment layer via spin-exchange interaction. We demonstrate typical Kondo characteristics in this artificial system, including heavy fermion behaviors and a sudden change in the size of the Fermi surface during the Kondo breakdown. By tuning the density of local moments, we observe a quantum phase transition between heavy fermions and orbital-selective Mott states. Our study provides a highly tunable Kondo lattice system for discovery of rich exotic states in the Kondo phase diagrams and a better understanding of Kondo-related physics. |
Wednesday, March 8, 2023 9:00AM - 9:12AM |
M30.00006: Quench Dynamics in the Multi-Channel Kondo system Iksu Jang, Po-Yao Chang The Sachdev-Ye-Kitaev(SYK) model is an interesting model which shows the non-Fermi liquid state and the quantum chaotic behavior with the exact solvability in the large-N limit. Recently, there have been many studies done about the non-equilibrium properties of the SYK model regarding quantum chaos and thermalization in strongly interacting systems. However, the SYK model is more likely a toy model which is difficult to realize in real systems despite there having been some proposals. In this study, instead of the SYK model, we used the Multi-Channel Kondo model, which has many similarities to the SYK model but is more realizable in the real system, to investigate the non-equilibrium properties of the non-Fermi liquid state under sudden quench of the Kondo coupling constant. Using the Keldysh formalism, we obtained the Kadanoff-Baym equations and solved them numerically. Under several different conditions such as initial temperature, we have observed the thermalization process. To analyze the thermalization process quantitatively, we calculated the final temperature and thermalization time. We also obtained the change of the spin susceptibility under the sudden quench which can be measured in the experiment. In addition, we are calculating the Lyanupov exponent to see the effects of quantum chaos on thermalization. |
Wednesday, March 8, 2023 9:12AM - 9:24AM |
M30.00007: First-principles study of Kondo effects in actinide- and lanthanide-based compounds Byungkyun Kang, Hyunsoo Kim, Sangkook Choi, Qiang Zhu, Chul-Hong Park Recent advances in research on quantum materials led to discoveries of fascinating superconductors such as paramagnetic heavy fermion UTe2, nickelates that are isostructural with high-Tc cuprates, and almost room temperature superconducting superhydrides under high pressure. A common thread of these superconductors is containing f and d electrons in lanthanide or actinide cations. However, it has been a great challenge to identify the role of the elements in the superconductivity due to its complex f and d electrons correlations. To explore the f and d entangled real systems, we employed ab-inito many-body perturbation theory combined with dynamical mean field theory (LQSGW+DMFT). In this talk, we will present the discovered Kondo effects in three materials. First, we found f-d Kondo effect in USbTe and its temperature dependence is in good agreement with ARPES. Second, we show the orbital selective Kondo effect in UTe2, which elucidates the anomalous temperature dependence of resistivity. Finally, we will discuss the impact of f-d Kondo cloud on the superconductivity of NdNiO2. |
Wednesday, March 8, 2023 9:24AM - 9:36AM Author not Attending |
M30.00008: $mathbb{Z}_3$ parafermion in the double charge-Kondo model Deepak Karki, Christophe Mora, Edouard Boulat, Andrew K Mitchell, Winston Pouse, David Goldhaber-Gordon Quantum impurity models with frustrated Kondo interactions can support quantum critical points with fractionalized excitations. |
Wednesday, March 8, 2023 9:36AM - 9:48AM |
M30.00009: Kondo enabled transmutation between spinons and superconducting vortices: origin of magnetic memory in 4Hb-$mathrm{TaS_2}$ Shizeng Lin Recent experiments [Persky {it{et al.}}, Nature {f{607}}, 692 (2022)] demonstrate a magnetic memory effect in 4Hb-$mathrm{TaS_2}$ above its superconducting transition temperature, where Abriokosov vortices are generated spontaneously by lowering temperature at zero magnetic field after field training the normal state. Motivated by the experiment, we propose the chiral quantum spin liquid (QSL) stabilized in the constituent layers of 4Hb-$mathrm{TaS_2}$ as a mechanism. We model 4Hb-$mathrm{TaS_2}$ as coupled layers of the chiral QSL and superconductor. Through the Kondo coupling between the localized moments and conduction electrons, there is mutual transmutation between spinons and vortices during the thermal cycling process, which yields magnetic memory effect as observed in experiments. We also propose a mechanism to stabilize the chiral and nematic superconductivity in 4Hb-$mathrm{TaS_2}$ through the Kondo coupling of conduction electrons to the chiral QSL. Our results suggest 4Hb-$mathrm{TaS_2}$ as an exciting platform to explore the interplay between QSL and superconductivity through the Kondo effect. |
Wednesday, March 8, 2023 9:48AM - 10:00AM |
M30.00010: Nonequilibrium Kondo effect in a Quantum Dot coupled to Ferromagnetic leads Anand Manaparambil, Andreas Weichselbaum, Jan von Delft, Ireneusz Weymann The accurate quantitative description of the nonequilibrium transport in interacting nanoscale junctions presents a formidable challenge. Tensor network methods have entered the arena as a highly competitive, versatile, and well-controlled approach. In particular, we use a recently developed hybrid numerical renormalization group-density matrix renormalization group thermofield quench approach based on a matrix product state framework. With this, we obtain quantitatively reliable predictions for spintronic transport through a Kondo-correlated quantum dot coupled to ferromagnetic leads in far-from-equilibrium conditions. We primarily study the bias dependence of the differential conductance through the system, which shows a finite zero-bias peak and a characteristic Kondo energy scale in the applied bias. We show that this Kondo scale decreases with an increase in the spin polarization on the leads and an exchange field can develop across the system. As a key result, we demonstrate that an additional external magnetic field can be utilized to achieve a full Kondo revival in an out-of-equilibrium setting. |
Wednesday, March 8, 2023 10:00AM - 10:12AM |
M30.00011: Fractional Kondo state near a band singularity in one-dimensional systems George B Martins, Marco M Suni, Patricia A Almeida, Marcos Sergio Figueira S Silva, Enrique V Anda, Sergio E Ulloa We present peculiar results for a Kondo state that is strongly affected by the proximity to the Fermi energy of a density of states ω-1/2 singularity (located at the bottom of the band). Signs of this effect are already visible at the single-particle (non-interacting) level. Indeed, a resonant state εd (the Anderson impurity energy level), located close to the band singularity, suffers a strong 'renormalization', where a bound state εb (delta function) is created below the bottom of the band, while the impurity level εd is pushed up to a renormalized position εdr. We note the very peculiar result that if εd is positioned right at the singularity, the spectral weight of the bound state εb is exactly 2/3. This is reminiscent of a result obtained for a three-dimensional electron gas subjected to a very strong spin-orbit interaction, treated in the continuum, as shown in PRB 93, 241111(R) (2016). The interacting system is modeled using the Single Impurity Anderson Model (SIAM), which is then solved using the Numerical Renormalization Group method. We provide a detailed description of the evolution of the Kondo state as the Fermi energy approaches the singularity, as well as when εd is placed at the singularity. |
Wednesday, March 8, 2023 10:12AM - 10:24AM |
M30.00012: Quantum oscillations of Kondo screening phases in strong magnetic fields Chung-Yu Mou, Po-Hao Chou, Chung-Hou Chung We generalize the method of numerical renormalization group to analyze the Kondo effect in strong magnetic fields, where the density of states for itinerary electrons at the chemical potential varies discontinuously as the magnetic field changes. We first examine phases of many-body ground states in the presence of single impurity. By investigating change of $z$-component of total spin, $Delta S_z$, and spin-spin correlation between the impurity and conduction electrons, we find that there are three states competing for the ground state when Zeeman splitting is present. One of the states is doublet in which the impurity spin is unscreened. The other two states are Kondo screening states with $Delta S_z=1/2$ and $Delta S_z=1$, in which the impurity spin is partially screened and completely screened respectively. For Kondo systems with two-impurities in strong magnetic fields, we find that the interplay between the Kondo screening effect, RKKY interaction, and quantum oscillations due to Landau levels determines the ground state of the system. Combination of these three factors results in different screening scenarios for different phases in which spins of two impurities can form spin-0 or spin-1 states, while impurity spins in these phases can be either screened, partially screened, or unscreened by conduction electrons. The emergence of these competing states as the ground state oscillates with the change of magnetic field, chemical potential or inter-impurity distance. This leads to quantum oscillations in magnetization and conductivity. In particular, we find extra peak structures in longitudinal conductivity that reflect changes of Kondo screening phases and are important features to be observed in experiments. Our results provide a complete characterization of phases for Kondo effect in strong magnetic fields. |
Wednesday, March 8, 2023 10:24AM - 10:36AM |
M30.00013: Kondo Lattice Semimetallic Behavior in NpTe1.75 Single Crystals William L Nelson, Ashini S Jayasinghe, Joseph M Sperling, Nicholas Beck, Todd N Poe, Daniel Murray, Narayan Poudel, Rory Kennedy, Susan Latturner, Thomas E Albrecht-Schoenzart, Krzysztof Gofryk, Ryan E Baumbach XRD, magnetic susceptibility, magnetization, heat capacity, and resistivity results are reported for single crystals of NpTe1.75 that were synthesized using iodine vapor transport. XRD and EDS measurements show that these crystals form in the layered tetragonal UAs2-type structure, with vacancies on the Te site. Magnetic susceptibility measurements reveal anisotropic paramagnetism, where Curie Weiss fits to the data yield a μeff of 3.6 μB/Np that is consistent with expectations for Np4+. Gradual deviation from this behavior is seen at low temperatures, which may be due to hybridization between f- and conduction electrons or crystal electric field effects. Heat capacity measurements reveal enhanced mass Fermi liquid behavior at low temperatures, as well as evidence for a possible phase transition at T = 1.5 K. Together with electrical resistivity measurements that show semimetallic behavior, these results indicate that hybridization between the f- and conduction electron states dominates the physics of NpTe1.75, leading to a hybridization gap semimetal. |
Wednesday, March 8, 2023 10:36AM - 10:48AM |
M30.00014: Charge density wave and vanishing drude weight in a one dimensional Kondo model Alexander Nikolaenko, Yahui Zhang, Subir Sachdev We propose to simulate Kondo transition in a bilayer optical lattice with a displacement field |
Wednesday, March 8, 2023 10:48AM - 11:00AM |
M30.00015: Excitonic instability in Kondo insulator. Abu S Musa Patoary, Hossein Dehghani, Victor M Galitski Kondo insulators (KI) are well known example of topological insulators. They are strongly interacting electronic systems where the hybridization between itinerant and localized electrons opens up a gap. KIs have been extensively studied for more than five decades. However, the study of excitonic phases in these materials is a relatively new research direction. Here, using a Bethe-Salpeter approach we study the exciton spectrum in these materials and we show that in some interaction strength regimes there can be an excitonic instability which leads to the formation of an excitonic insulator (EI) phase. Correspondingly, we calculate the gap and critical temperature of the EI phase using a mean-field approach. |
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