In one-dimensional, two-dimensional and three-dimensional systems, a wide variety of novel properties has been discovered, like 1D magnetism, topological insulator and Weyl semiconductor. In this talk, high pressure was employed to tune the crystal structure and studied the electronic structure evolution and comprehensive quantum behavior by using experimental measurements and theoretical calculations.

We report systematical studies of a new quasi-one-dimensional (1D) compound Ba₃TiTe₅ and the high-pressure induced superconductivity therein. Ba₃TiTe₅ is a well-defined 1D conductor and thus, it can be considered a starting point to explore the exotic physics induced by pressure via enhancing the interchain hopping to move the 1D conductor to a high dimensional metal. The superconductivity emerges from 8.8 GPa, near which the Umklapp gap is mostly suppressed. T_c is enhanced and reaches the maximum ~6 K at about 36.7 GPa, where the spin/charge density wave (SDW/CDW) is completely suppressed, and a non-Fermi Liquid behavior appears. Our results suggest that the appearance of superconductivity is associated with the fluctuation due to the suppression of Umklapp gap and the enhancement of T_c is related with the fluctuation of the SDW/CDW. A thorough study of superconductivity and phase transitions in a quasi-hydrostatically pressurized Bi₄Br₄ crystal. Pressure-induced insulator-metal, superconductive, and structural transitions have been demonstrated in a pressurized Bi₄Br₄ crystal, which lays the foundation for further understanding the physics in this unique quasi-one-dimensional system.