arXiv subjects

Hong-Yan Lu

Publications and source records attributed to Hong-Yan Lu.

24 records · Page 2Linked to original sources

arXiv2018

Electronic structure and nontrivial topological surface states in ZrRuP and ScPd$_{3}$ compounds

In this paper, we investigate the topological properties of ZrRuP and ScPd$_{3}$ using the first-principles calculations. We calculate the electronic structure, surface states, and Z$_{2}$ topological invariant. The band structure of ZrRuP without the spin-orbit coupling (SOC) exhibits a nodal line located at $Γ$-K-M high symmetry line in the Brillouin zone(BZ). The nodal line is protected by the mirror symmetry corresponding to the plane $k_{z}=0$. The geometry of Fermi surface is a connected torus centered at K point with open orbits at the boundary of BZ, when the Fermi level is shifted up 0.25 eV. The inclusion of SOC leads to the gap opening in the band structure which corresponds adiabatically to transition from nodal line semimetal to topological insulator. The corresponding surface states were obtained from thin film calculations, and the result shows surface states emerging along the gap region. We also identify the ScPd$_{3}$ compound as a Dirac nodal line semimetal. This structure has nontrivial surface states and the corresponding Z$_{2}$ topological invariant is (1;000). Both the ScPd$_{3}$ and ZrRuP have the Fermi surfaces of the bands which make nodal lines with open orbits.

cond-mat.mtrl-sci↗

arXiv2017

Type-II Dirac cone and Dirac cone protected by nonsymmorphic symmetry in carbon-lithium compound (C4Li)

In this work, we predict a novel band structure for Carbon-Lithium(C4Li) compound using the first-principles method. We show that it exhibits two Dirac points near the Fermi level; one located at W point originating from the nonsymmophic symmetry of the compound, and the other one behaves like a type-II Dirac cone with higher anisotropy along the Γ to X line. The obtained Fermi surface sheets of the hole-pocket and the electron-pocket near the type-II Dirac cone are separated from each other, and they would touch each other when the Fermi level is doped to cross the type-II Dirac cone. The evolution of Fermi surface with doping is also discussed. The bands crossing from T to W make a line-node at the intersection of kx=π and ky=π mirror planes. The C4Li is a novel material with both nonsymmorphic protected Dirac cone and type-II Dirac cone near the Fermi level which may exhibit exceptional topological property for electronic applications.

cond-mat.mtrl-sci↗

arXiv2016

Spinon Majorana fermions

A realization of Majorana fermions is proposed in the frustrated magnets via the topological proximity effect. Specifically, we consider a theoretical model, where a topological insulator is coupled to a frustrated magnetic material through the spin exchange interaction. Using the renormalization group-based self-consistent mean-field approach, and calculating the self-energy correction due to the topological insulator, we find that the spin texture and the spin-momentum locking of the Dirac cone will be inherited by the spinons in the nearby frustrated magnets. This leads to a particular topological state of matter that supports the Majorana excitations. Unlike the conventional realization in SC systems, these Majorana fermions are the combination of spinons and anti-spinons, rather than electrons and holes. They can participate in the transport of spinons, leading to nontrivial properties of the spin transport.

cond-mat.str-el↗

arXiv2016

Ferromagnetism and superconductivity with possible $p+ip$ pairing symmetry in partially hydrogenated graphene

By means of first-principles calculations, we predict two new types of partially hydrogenated graphene systems: C$_{6}$H$_{1}$ and C$_{6}$H$_{5}$, which are shown to be ferromagnetic (FM) semimetal and FM narrow-gap semiconductor, respectively. When properly doped, the Fermi surface of the two systems consists of an electron pocket or six hole patches in the first Brillouin zone with completely spin-polarized charge carries. If superconductivity exists in these systems, the stable pairing symmetries are shown to be $p+ip$ for electron doped case, and anisotropic $p+ip$ for hole doped case. The predicted systems may provide fascinating platforms for studying the novel properties of ferromagnetism and triplet-pairing superconductivity as well as two-dimensional spintronics.

cond-mat.supr-con↗

arXiv2007

Impurity resonance states in electron-doped high T_c superconductors

Two scenarios, i.e., the anisotropic s-wave pairing (the s-wave scenario) and the d-wave pairing coexisting with antiferromagnetism (the coexisting scenario) have been introduced to understand some of seemingly s-wave like behaviors in electron doped cuprates. We considered the electronic structure in the presence of a nonmagnetic impurity in the coexistence scenario. We found that even if the AF order opens a full gap in quasi-particle excitation spectra, the mid-gap resonant peaks in local density of states (LDoS) around an impurity can still be observed in the presence of a d-wave pairing gap. The features of the impurity states in the coexisting phase are markedly different from the pure AF or pure d-wave pairing phases, showing the unique role of the coexisting AF and d-wave pairing orders. On the other hand, it is known that in the pure s-wave case no mid-gap states can be induced by a nonmagnetic impurity. Therefore we proposed that the response to a nonmagnetic impurity can be used to differentiate the two scenarios.

cond-mat.supr-con↗

arXiv2006

Disentangling single-particle gap by electronic Raman absorption in electron-doped cuprates

In the under- to optimal-doping regimes of electron-doped cuprates, it was theoretically suspected that there is a coexistence of superconducting (SC) and antiferromagnetic (AFM) orders. The quasi-particle excitations could be gapped by both orders, and the effective gap is non-monotonic d-wave-like in the momentum space. Alternatively the gap was also speculated as a pure pairing gap. Using an effective microscopic model, we consider the manifestation of the quasi-particle gap in the electronic Raman spectra in a range of doping levels, where the relative strength of the SC and AFM order parameters varies. We demonstrate that from the electronic Raman spectra the effective single-particle gap can be disentangled into contributions from the two distinctive orders. This would help to tell whether the non-monotonic gap is due to the coexistence of SC and AFM orders.

cond-mat.supr-con↗