Topological phases and bulk-edge correspondence of magnetized cold plasmas

Abstract

Plasmas have been recently studied as topological materials. However, a comprehensive picture of topological phases and topological phase transitions in cold magnetized plasmas is still missing. Here we systematically map out all the topological phases and establish the bulk-edge correspondence in cold magnetized plasmas. We find that for the linear eigenmodes, there are 10 topological phases in the parameter space of density n, magnetic field B, and parallel wavenumber kz, separated by the surfaces of Langmuir wave-L wave resonance, Langmuir wave-cyclotron wave resonance, and zero magnetic field. For fixed B and kz, only the phase transition at the Langmuir wave-cyclotron wave resonance corresponds to edge modes. A sufficient and necessary condition for the existence of this type of edge modes is given and verified by numerical solutions. We demonstrate that edge modes exist not only on a plasma-vacuum interface but also on more general plasma-plasma interfaces. This finding broadens the possible applications of these exotic excitations in space and laboratory plasmas.

The dispersion and propagation of topological Langmuir-cyclotron waves in cold magnetized plasmas

“…Surface waves in plasmas have been extensively studied [1-3] due to their wide range of applications [4][5][6][7][8][9]. Recently, a new class of surface modes in plasma produced by topological phase transition have been investigated [10,11]. Here, we report studies on the dispersion and propagation of the newly identified topological surface mode called Topological Langmuir-Cyclotron Wave (TLCW) in cold magnetized plasmas.…”

“…When variation in the z-direction can be ignored, i.e., k z = 0, Chern numbers for the X waves in 2D plasmas were calculated [34,35] and related to surface waves via the bulk-edge correspondence [36]. When k z = 0, the non-trivial topology of the plasma as a 2D system were found [10,37] and its topological phase diagram was established [11]. In particular, underdense plasmas can be regarded as a Weyl semimetal [38,39] and host a surface state with the Fermi-arc structure [17].…”

“…The topological surface wave in the present study is called Topological Langmuir-Cyclotron Wave (TLCW), because it is localized at the interface between two plasmas in different topological phases separated by the phase transition at the resonance between the Langmuir wave and the cyclotron wave [11]. Based on a one-dimensional model, we study the dispersion of the TLCW using its isofrequency contours, from which the main physical properties of the TLCW, such as the unidirectional (chiral) propagation and the immunity of scattering, can be directly observed.…”

Continuum damping of topologically-protected edge modes at the boundary of a magnetized plasma

“…Here subscript x, y, z show the component of electromagnetic fields in x−, y− and z− direction, (1-4) over the PVI. For low frequency SPW's on SPVI, transverse permittivity t remains positive everywhere and the waves propagate without damping [11,12]. The boundary conditions turn out to be…”

“…Recently, topological properties of edge states (surface plasma waves; SPW's), occurring at the boundary of cold magnetized plasma, have been explored [8][9][10][11][12][13] and it has been shown that for certain choices of plasma density (n), stationary external magnetic field (B 0 = B 0 ẑ) and parallel wavenumber k z , SPW's can exist at the plasma-vacuum [11] or plasma-plasma interface, provided both plasmas have different topological phase [12].…”