Terahertz radiation induced circular Hall effect in graphene

Light-induced phase crossovers in a quantum spin Hall system

“…In this work, based on numerical calculations with high-frequency Floquet expansion, we find that circularly polarized light can break the timereversal symmetry and introduce the QAH phase in HgTe quantum well. Our findings complement other works that utilizes circularly polarized light to induce new topological phases in Graphene [41][42][43][44][45][46][47][48][49][50][51], but with significant differences. In particular, the coupling between the edge states is spin dependent, and it is related not only to the width of the system but also to the strength of the polarized pumping optics.…”

Optical Conductivity Signatures of Floquet Electronic Phases

“…Furthermore, a non-zero anomalous Hall conductivity of 1.8 ± 0.4 e 2 /h was detected, which can be explained partially by the generation of topologically non-trivial Floquet-Bloch bands [22]. A subsequent experimental paper also found a radiation-induced anomalous Hall conductivity in graphene [20].…”

“…Based on that, observable quantities should be theoretically determined in order to make contact with experiments. Two techniques that have been utilized are time-and angleresolved photoemission spectroscopy (TR-ARPES) [12][13][14][15][16][17][18] and DC electronic transport measurements [19,20], each with their own benefits and limitations.…”

“…While TR-ARPES is a powerful technique for detecting dynamically renormalized energy bands, resolving the dispersion over the entire high-symmetry lines is challenging, due to the fact that the high intensities required restrict pulse lengths to picosecond timescales [12][13][14][15][16][17][18]. Additionally, while DC electronic transport can detect the size of gap openings and topological transitions via jumps in the anomalous Hall conductivity, the dispersion of the quasienergy band structure is not determined [19,20].…”