arXiv subjects

Yen-Wen Lu

Publications and source records attributed to Yen-Wen Lu.

5 recordsLinked to original sources

arXiv2025

Interaction-enhanced quantum to classical transport crossover temperature in a Luttinger liquid

Strange metals are highly entangled gapless states of matter that exhibit anomalous transport, such as linear in temperature resistivity, over more than a decade of temperature. Why a single power law should be so robust is an open question. We propose a scenario in which interactions enhance the domain of certain scattering regimes, effectively suppressing other ``would-be regimes." We test this proposal in a one-dimensional Luttinger liquid coupled to a one-dimensional acoustic phonon. We use the memory matrix formalism to calculate the dc electrical and thermal conductivities at low and high temperatures, relative to the Debye cutoff on phonon frequencies, in both the ``clean" (umklapp scattering) and ``dirty" (disorder scattering) limits. We find the crossover temperature separating the low and high temperature regimes to be interaction-dependent, with repulsive interactions substantially increasing it, generally by more than an order of magnitude. This provides a concrete illustration for how interactions can extend a single transport regime over a wider temperature range.

cond-mat.str-el↗

arXiv2023

Weiss Oscillations in the Galilean-Invariant Dirac Composite Fermion Theory for Even-Denominator Filling Fractions of the Lowest Landau Level

Standard field theoretic formulations of composite fermion theories for the anomalous metals that form at or near even-denominator filling fractions of the lowest Landau level do not possess Galilei invariance. To restore Galilei symmetry, these theories must be supplemented by "correction" terms. We study the effect of the leading "correction" term, known as the dipole term, in the Dirac composite fermion theory (a theory that consists of a Dirac fermion coupled to an Abelian Chern-Simons gauge field) on quantum oscillations in the electrical resistivity due to a periodic scalar potential about even-denominator filling fractions. We find the dipole term to be insufficient to resolve the systematic discrepancy, discovered in [Kamburov et. al., Phys. Rev. Lett. 113, 196801 (2014)], between the locations of the oscillation minima predicted by Dirac composite fermion theory without Galilei invariance and those observed in experiment. Further, in contrast to [Hossain et al., Phys. Rev. B 100, 041112 (2019)], we find the quantum oscillations about the half-filled and quarter-filled lowest Landau level to have qualitatively similar behavior. This analysis uses a mean-field approximation, in which gauge field fluctuations are neglected. Based on this and previous analyses, we speculate the discrepancy with experiment may be an indirect signature of the effect of gauge field fluctuations in composite fermion theory.

cond-mat.str-el↗

arXiv2023

Topological Kondo Superconductors

Spin-triplet $p$-wave superconductors are promising candidates for topological superconductors. They have been proposed in various heterostructures where a material with strong spin-orbit interaction is coupled to a conventional $s$-wave superconductor by proximity effect. However, topological superconductors existing in nature and driven purely by strong electron correlations are yet to be studied. Here we propose a realization of such a system in a class of Kondo lattice materials in the absence of spin-orbit coupling and proximity effect. Therein, the odd-parity Kondo hybridization mediates ferromagnetic spin-spin coupling and leads to spin-triplet resonant-valence-bond ($t$-RVB) pairing between local moments. Spin-triplet $p\pm i p^\prime$-wave topological superconductivity is reached when Kondo effect co-exists with $t$-RVB. We identify the topological nature by the non-trivial topological invariant and the Majorana fermions at edges. Our results offer a comprehensive understanding of experimental observations on UTe$_2$, a U-based ferromagnetic heavy-electron superconductor.

cond-mat.str-el↗

arXiv2020

Enhanced quantum oscillations in Kondo insulators

Quantum oscillations have long been regarded as the manifestation of the Fermi surface in metals. However, they were recently observed in Kondo insulators. We examine the Kondo screening due to Landau levels in Kondo insulators. It is shown that even for large Kondo insulating gaps, appreciable amplitudes of quantum oscillations that are consistent with experimental observations are present both in magnetization and resistivity. Specifically, we show that due to the periodic alignment between the Landau levels in the conduction and the f-orbit electrons, the Kondo screening itself undergoes oscillations so that the electronic structure oscillates with the magnetic field. Our results explain main features of quantum oscillations observed in experiments. They indicate that the non-rigidity of the electronic structure results in observable quantum oscillations Kondo insulators. This new effect provides a new way to probe the Fermi surface geometry of insulators.

cond-mat.str-el↗

arXiv2019

Tunable topological semi-metallic phases in Kondo lattice systems

We exploit topological semi-metallic phases resulting from the Kondo screening in Anderson lattice models. It is shown that by including spin-orbit interactions both in the bulk electrons and in the hybridization between the conduction electrons and electrons in $f$ orbit, all types of topological semi-metallic phases can be realized in Anderson lattice models. Specifically, upon either time-reversal symmetry broken or inversion symmetry broken, we find that either Weyl semi-metallic phase, Dirac semi-metallic phase or nodal-ring semi-metallic phases always emerge between insulating phases and can be accessed by tuning either temperature or spin-orbit interaction. For Anderson lattice models with general 3D spin-orbit hybridization between the conduction electrons and electrons in $f$ orbit, we find that Weyl nodal-ring semi-metallic phases emerges between strong and weak topological insulating phases. Furthermore, in the presence of an exchange field, Weyl semi-metallic phases forms after two Weyl points of charge $\pm1$ split off from a Dirac point at time-reversal momenta. On the other hand, when the spin-orbit interaction is included in the conduction electron, we find that upon the rotation symmetry being broken with anisotropic hopping amplitudes, Weyl semi-metallic phase emerges with double Weyl node of charges of $\pm2$. Furthermore, the Weyl semi-metallic phases with charges of $\pm2$ can be tuned into Weyl semi-metallic phases with charges of $\pm1$ through the inclusion of the Rashba spin-orbit interaction. Our analyses indicate that Anderson lattices with appropriate spin-orbit interactions provide a platform for realizing all types of topological semi-metallic phase

cond-mat.str-el↗