Tunable Weyl Points in Periodically Driven Nodal Line Semimetals

Abstract

Weyl semimetals and nodal line semimetals are characterized by linear band touching at zero-dimensional points and one-dimensional lines, respectively. We predict that a circularly polarized light drives nodal line semimetals into Weyl semimetals. The Floquet Weyl points thus obtained are tunable by the incident light, which enables investigations of them in a highly controllable manner. The transition from nodal line semimetals to Weyl semimetals is accompanied by the emergence of a large and tunable anomalous Hall conductivity. Our predictions are experimentally testable by transport measurement in film samples or by pump-probe angleresolved photoemission spectroscopy. 71.70.Ej,75.70.Tj It has become well known that topological concepts underlie many fascinating phenomena in condensed matter physics. After in-depth investigations of topological insulators [1][2][3], considerable attention is now focused on topological semimetals. Unlike topological insulators, whose gapless excitations always live at the sample boundary, topological semimetals host gapless fermions in the bulk. The two major classes of topological semimetals under intense study are (i) nodal point semimetals and (ii) nodal line semimetals (NLSM). The nodal point semimetals include Dirac semimetals(DSM) [4][5][6][7][8][9][10][11][12][13][14] and Weyl semimetals(WSM) [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31]. The main feature of the band structures of DSMs and WSMs is the linear bandtouching points ("Dirac points" and "Weyl points"), which are responsible for most of their interesting properties, including novel phenomena induced by the chiral anomaly [32][33][34][35][36][37][38][39][40][41][42][43][44]. NLSMs [45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63] differ in that they contain band-touching lines or rings [107], away from which the dispersion is linear.In this Letter we show that driving NLSMs by a circularly polarized light (CPL) creates WSMs, namely, nodal lines become nodal points under radiations. Our work was motivated by recent progress in Floquet topological states [64][65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83], in particular, Ref. [84] showed that incident light can shift the locations of Weyl points in WSMs. The effect we predict in NLSMs is more dramatic: band-touching lines are driven to points; thus, the dimension of the band-touching manifold is changed. Meanwhile, a large anomalous Hall conductivity tunable by the incident light emerges. Unlike the photoinduced Hall effect in WSMs [84], which is proportional to intensity of incident light, the Hall conductivity in our systems is large and quite insensitive to the light intensity at low temperature, though it depends sensitively on the incident angle of light. The surface Fermi arcs of the Floquet WSMs have a simple interpretation, namely, it comes from tilting the drumhead surface dispersion of NLSMs.The Floquet WSMs derived from NLSMs are highly tunable, in particular, the Weyl poi...

Monitoring Electron-Photon Dressing in WSe2

“…Other recent Floquet-topological phenomena include nodal rings, 15 type-II Floquet-Weyl semimetals 16 , carbon nanotubes 17 and soundwaves 18 among others.…”

0−π transitions in a Josephson junction of an irradiated Weyl semimetal

“…The observation of such oscillations could be a direct proof of the existence of the chiral nodes, but since the momentum separation of the chiral nodes remains fixed for a given material, it is not likely to be usable as a tuning parameter. On the other hand, it has also been understood recently how time periodic perturbations can affect the WSM [37][38][39][40][41][42] , and in particular, how a high frequency incident elliptically polarized light can slightly modify the position of the effective chiral nodes of the WSM 43 . This provides the possibility that the external parameters controlling the perturbation can serve as tuning parameters in adjusting the separation of the chiral nodes.…”

Photoinduced topological phase transition from a crossing-line nodal semimetal to a multiple-Weyl semimetal

“…A typical example is the generation of a Weyl point from a Dirac semimetal [42][43][44][45] . It is shown that a Weyl node can also be generated by applying photoirradiation to a loop nodal semimetal 46,47 . In this paper, we first propose a simple scheme to construct models for crossing-line nodal semimetals.…”