Floquet Weyl semimetal induced by off-resonant light

Wang, Rui; Wang, Baigeng; Shen, R.; Sheng, L.; Xing, D. Y.

doi:10.1209/0295-5075/105/17004

Cited by 135 publications

(103 citation statements)

References 37 publications

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“…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.…”

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confidence: 99%

Tunable Weyl Points in Periodically Driven Nodal Line Semimetals

2016

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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...

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confidence: 99%

Tunable Weyl Points in Periodically Driven Nodal Line Semimetals

2016

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“…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.…”

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

2017

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We propose a setup for the experimental realization of anisotropic 0-π transitions of the Josephson current, in a junction whose link is made of irradiated Weyl semi-metal (WSM), due to the presence of chiral nodes. The Josephson current through a time-reversal symmetric WSM has anisotropic (with respect to the orientation of the chiral nodes) periodic oscillations as a function of k0L, where k0 is the (relevant) separation of the chiral nodes and L is the length of the sample. We then show that the effective value of k0 can be tuned with precision by irradiating the sample with linearly polarized light, which does not break time-reversal invariance, resulting in 0-π transitions of the critical current. We also discuss the feasibility and robustness of our setup.

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“…By using Floquet theory [23][24][25][26], it can be shown that such a driving field can modify the topology of the system's band structure. This method has been used to generate several topological phases such as Floquet topological insulators [27,28] and Floquet Weyl semimetals [29]. Our recent studies have also shown how a variety of novel topological phases emerge in a periodically driven system [30].…”

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confidence: 98%

Generating controllable type-II Weyl points via periodic driving

Bomantara

Gong

2016

Phys. Rev. B

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Type-II Weyl semimetals are a novel gapless topological phase of matter discovered recently in 2015. Similar to normal (type-I) Weyl semimetals, type-II Weyl semimetals consist of isolated band touching points. However, unlike type-I Weyl semimetals which have a linear energy dispersion around the band touching points forming a three dimensional (3D) Dirac cone, type-II Weyl semimetals have a tilted cone-like structure around the band touching points. This leads to various novel physical properties that are different from type-I Weyl semimetals. In order to study further the properties of type-II Weyl semimetals and perhaps realize them for future applications, generating controllable type-II Weyl semimetals is desirable. In this paper, we propose a way to generate a type-II Weyl semimetal via a generalized Harper model interacting with a harmonic driving field. When the field is treated classically, we find that only type-I Weyl points emerge.However, by treating the field quantum mechanically, some of these type-I Weyl points may turn into type-II Weyl points. Moreover, by tuning the coupling strength, it is possible to control the tilt of the Weyl points and the energy difference between two Weyl points, which makes it possible to generate a pair of mixed Weyl points of type-I and type-II. We also discuss how to physically distinguish these two types of Weyl points in the framework of our model via the Landau level structures in the presence of an artificial magnetic field. The results are of general interest to quantum optics as well as ongoing studies of Floquet topological phases.

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Floquet Weyl semimetal induced by off-resonant light

Cited by 135 publications

References 37 publications

Tunable Weyl Points in Periodically Driven Nodal Line Semimetals

Tunable Weyl Points in Periodically Driven Nodal Line Semimetals

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

Generating controllable type-II Weyl points via periodic driving

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