High-temperature superconductivity stabilized by electron-hole interband coupling in collapsed tetragonal phase of KFe2As2 under high pressure

Abstract

We report a high-pressure study of simultaneous low-temperature electrical resistivity and Hall effect measurements on high quality single-crystalline KFe2As2 using designer diamond anvil cell techniques with applied pressures up to 33 GPa. In the low pressure regime, we show that the superconducting transition temperature T_c finds a maximum onset value of 7 K near 2 GPa, in contrast to previous reports that find a minimum T_c and reversal of pressure dependence at this pressure. Upon applying higher pressures, this T_c is diminished until a sudden drastic enhancement occurs coincident with a first-order structural phase transition into a collapsed tetragonal phase. The appearance of a distinct superconducting phase above 13 GPa is also accompanied by a sudden reversal of dominant charge carrier sign, from hole- to electron-like, which agrees with our band calculations predicting the emergence of an electron pocket and diminishment of hole pockets upon Fermi surface reconstruction. Our results suggest the high-temperature superconducting phase in KFe2As2 is substantially enhanced by the presence of nested electron and hole pockets, providing the key ingredient of high-T_c superconductivity in iron pnictide superconductors.

5 pages, 4 figures; Phys. Rev. B - Rapid Communications (in press)

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• Superconducting and magnetic phase diagram of RbEuFe4As4 and CsEuFe4As4 at high pressure
• Origin of the superconducting state in the collapsed tetragonal phase of KFe2As2
• Origin of Pressure-induced Superconducting Phase in K${}_x$Fe${}_{2-y}$Se${}_2$ studied by Synchrotron X-ray Diffraction and Spectroscopy
• Ab-initio perspective on structural and electronic properties of iron-based superconductors
• Fermi-surface topological phase transition and horizontal order-parameter nodes in CaFe${}_2$As${}_2$ under pressure
• Observation of Two Collapsed Phases in CaRbFe4As4
• Non-trivial role of interlayer cation states in iron-based superconductors
• Structural, electronic, and dynamical properties of the tetragonal and collapsed tetragonal phases of KFe${}_2$As${}_2$
• Impact of disorder on the superconducting transition temperature near a Lifshitz transition
• Interband electron pairing for superconductivity from the breakdown of the Born-Oppenheimer approximation
• Possible superconducting fluctuation and pseudogap state above $T_c$ in CsFe${}_2$As${}_2$
• Quantum Oscillations in the Anomalous Spin Density Wave State of FeAs
• Nearly ferromagnetic metal state in the collapsed tetragonal phase of YFe${}_2$(Ge,Si)${}_2$
• Pressure induced antiferromagnetic-tetragonal to nonmagnetic-collapse-tetragonal insulator-metal transition in ThMnAsN
• Universal quasi-degenerate orbital origin of two-dome phases in iron pnictide superconductors
• Superconducting density of states and vortex lattice of LaRu${}_2$P${}_2$ observed by Scanning Tunneling Spectroscopy
• Enhanced critical temperatures in the strongly overdoped iron-based superconductors AFe${}_2$As${}_2$ (A = K, Cs, Rb) observed by point contacts
• Photochemical Synthesis of P-S-H Ternary Hydride at High Pressures
• Influence of growth flux solvent on anneal-tuning of ground states in CaFe2As2