Photocurrent response in parity-time symmetric current-ordered states

Abstract

Parity-time-reversal symmetry (PT symmetry), a symmetry for the combined operations of space inversion (P) and time reversal (T ), is a fundamental concept of physics and characterizes the functionality of materials as well as P and T symmetries. In particular, the PT -symmetric systems can be found in the centrosymmetric crystals undergoing the parity-violating magnetic order which we call the odd-parity magnetic multipole order. While this spontaneous order leaves PT symmetry intact, the simultaneous violation of P and T symmetries gives rise to various emergent responses that are qualitatively different from those allowed by the nonmagnetic P-symmetry breaking or by the ferromagnetic order. In this review, we introduce candidates hosting the intriguing spontaneous order and overview the characteristic physical responses. Various off-diagonal and/or nonreciprocal responses are identified, which are closely related to the unusual electronic structures such as hidden spin-momentum locking and asymmetric band dispersion. Contents I. Introduction II. Magnetic Parity Violation and Space-Time Symmetry A. Parity-time-reversal symmetry and parity violations B. Hidden Magnetic Degrees of Freedom in Crystals C. Multipolar degree of freedom of visible antiferromagnets III. Emergent Responses of PT -symmetric magnets A. Electric-Magnetic Classification of Response Function B. Magnetic Counterpart of Piezoelectric Effect C. Nonreciprocal Property of Electronic Transport and Optical Response 1. Nonreciprocal conductivity 2. Photocurrent generation IV. Availability of PT -symmetric Magnets and Physical Properties A. Switching the compensated magnets B. Control of electronic property with PT -symmetric magnetic order V.

Imaginary spin-orbital coupling in parity-time symmetric systems with momentum-dependent gain and loss

“…This imaginary SOC Hamiltonian is PT -symmetric, with the parity operator P exchanging the two spin components, and the operator T performing the complex conjugation [35]. We also note that there already exist some researches combining SOC and PT symmetry [80][81][82][83][84], however in these works it is a conventional Hermitian SOC term and a PT -symmetric term been stiffly glued. In contrast, here the SOC term itself is non-Hermitian.…”

Theoretical Understanding of Nonlinear Optical Properties in Solids: A Perspective

“…In addition to the shift current, the injection current and spin current are also recognized as key contributors to the second-order nonlinear optics. Typically employed in magnetic materials, these phenomena present distinct characteristics. − In nonmagnetic materials, the injection current vanishes under linearly polarized incident light, leading discussions to focus primarily on circularly polarized light. Recent advancements in two-dimensional magnetic materials have renewed interest in their electronic and optical properties, especially regarding their PBVE effect. − The breakdown of the time-reversal symmetry in magnetic materials allows for the generation of injection currents under linear illumination.…”

Topological Insulator Metamaterials

“…Nanostructuring of electronic topological materials with elements introducing either intrinsic or extrinsic (by arrangement) electromagnetic chirality gives the opportunity to study how fundamental symmetries manifest optically in electronic topological systems. While theoretical and experimental studies of PT-symmetries abound in non-Hermitian optical systems, where on-site gain and losses can be finely tailored, their relevance to photoinduced phenomena in condensed matter topological systems is just being recognized. − Sculpting of the optical nearfield by metamaterials brings about intriguing questions like the effects that optically induced local anisotropy, birefringence, chirality, asymmetric absorptions, or more complex, highly structured optical fields would have on electronic topology and its manifestations. The implementation of photonic metamaterials to enhance, isolate, and manipulate the spin-polarized surface states of topological insulators provides new ways to control light–matter interaction in topological materials and paves the way toward realization of chiral photodetectors with tailored spectral and polarization response.…”