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Angle-resolved upper critical field $H_{c2}$ provides an efficient tool toprobe the gap symmetry of unconventional superconductors. We revisit thebehavior of in-plane $H_{c2}$ in $d$-wave superconductors by considering boththe orbital effect and Pauli paramagnetic effect. After carrying out systematicanalysis, we show that the maxima of $H_{c2}$ could be along either nodal orantinodal directions of a $d$-wave superconducting gap, depending on thespecific values of a number of tuning parameters. This behavior is in contrastto the common belief that the maxima of in-plane $H_{c2}$ are along thedirection where the superconducting gap takes its maximal value. Therefore,identifying the precise $d$-wave gap symmetry through fitting experimentsresults of angle-resolved $H_{c2}$ with model calculations at a fixedtemperature, as widely used in previous studies, is difficult and practicallyunreliable. However, our extensive analysis of angle-resolved $H_{c2}$ showthat there is a critical temperature $T^{*}$: in-plane $H_{c2}$ exhibits itsmaxima along nodal directions at $T < T^{*}$ and along antinodal directions at$T^{*} < T < T_c$. The concrete value of $T^{*}$ may change as other parametersvary, but the existence of $\pi/4$ shift of $H_{c2}$ at $T^{\ast}$ appears tobe a general feature. Thus a better method to identify the precise $d$-wave gapsymmetry is to measure $H_{c2}$ at a number of different temperatures, andexamine whether there is a $\pi/4$ shift in its angular dependence at certain$T^{*}$. We further show that Landau level mixing does not change this generalfeature. However, in the presence of Fulde-Ferrell-Larkin-Ovchinnikov state,the angular dependence of $H_{c2}$ becomes quite complicated, which makes itmore difficult to determine the gap symmetry by measuring $H_{c2}$.

Connection between in-plane upper critical field $H_{c2}$ and gap symmetry in layered $d$-wave superconductors revisited