Correlation-driven organic 3D topological insulator with relativistic fermions

Abstract

Exploring new topological phenomena and functionalities induced by strong electron correlation has been a central issue in modern condensed-matter physics. One example is a topological insulator (TI) state and its functionality driven by the Coulomb repulsion rather than a spin-orbit coupling. Here, we report a ‘correlation-driven’ TI state realized in an organic zero-gap system α-(BETS)2I3. The topological surface state and chiral anomaly are observed in temperature and field dependences of resistance, indicating a three-dimensional TI state at low temperatures. Moreover, we observe a topological phase switching between the TI state and non-equilibrium Dirac semimetal state by a dc current, which is a unique functionality of a correlation-driven TI state. Our findings demonstrate that correlation-driven TIs are promising candidates not only for practical electronic devices but also as a field for discovering new topological phenomena and phases.

Band Structure Evolution during Reversible Interconversion between Dirac and Standard Fermions in Organic Charge-Transfer Salts

“…Below, we briefly summarize the structural and physical properties of α-D 2 I 3 . These properties are known [19][20][21][22][23][24][25][26][45][46][47][48][49][50], but are necessary for proving the validity of our calculated band structures. As the observed electronic properties and calculated band structures in previous papers do not always provide necessary information for comparison with our calculated band structures in detail, we re-examined the physical properties shown below.…”

“…In our calculation, α-BETS 2 I 3 retained the metallic band structure down to 30 K. However, the electrical resistivity of α-BETS 2 I 3 smoothly commenced to increase at ~50 K (Figure 2a), while the magnetic susceptibility took the broad minimum at ~30 K (Figure 2c). These observed electronic behaviors suggest the significant effects of fluctuation and/or strong electron correlation at low T in α-BETS 2 I 3 [22]. The calculated band structures would be inconsistent with the observed electronic properties owing to fluctuation and/or strong electron correlation, because they were not considered in the calculation.…”

“…The organic charge-transfer (CT) salts α-D 2 I 3 (D = C 10 H 8 S 8 (ET), C 10 H 8 S 6 Se 2 (STF), and C 10 H 8 S 4 Se 4 (BETS); Figure 1b) under ambient pressure are extensively studied, as well as their aspects regarding organic DF systems [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62]. However, most studies on them are focused on whether they belong to the zero-gap semiconductors (ZGSs) [19][20][21][22][23][24][25][26][27][28][29][30]…”

Structural and morphological investigation of (R)-α-phenylethylammonium-oxalate in bulk vs. nanowires on a modified substrate surface

“…29,30 Organic conductor, bis(ethylenedithio) tetraselenafulvalene have been explored as a part of topological insulators. 31 A distinct type of organic semiconductors that serve as a versatile foundation for electrical, spintronic, and energy-harvesting devices show dependence of structural modications, particularly in terms of electrical, optical, and dielectric properties. 32 Very popular application of organics is as an insulators.…”

Ultrafast Pump–Probe Spectroscopy in Organic Dirac Electron Candidate α-(BETS)2I3

“…On the other hand, resistivity gradually increases with a decreasing temperature below T MI = 50 K and a step-like change at around 40 K, and these origins are still controversial [11]. To date, theoretical studies [12,13], as well as various transport and magnetic measurements [14][15][16][17][18][19], have been conducted to elucidate the rise in resistivity. However, time-resolved spectroscopic measurements are still lacking.…”